- Extended getuid() to replace figure_curuserid().

[roundup.git] / doc / customizing.txt

===================
Customising Roundup
===================

:Version: $Revision: 1.97 $

.. This document borrows from the ZopeBook section on ZPT. The original is at:
   http://www.zope.org/Documentation/Books/ZopeBook/current/ZPT.stx

.. contents::
   :depth: 1

What You Can Do
===============

Before you get too far, it's probably worth having a quick read of the Roundup
`design documentation`_.

Customisation of Roundup can take one of five forms:

1. `tracker configuration`_ file changes
2. database, or `tracker schema`_ changes
3. "definition" class `database content`_ changes
4. behavioural changes, through detectors_
5. `access controls`_
6. change the `web interface`_

The third case is special because it takes two distinctly different forms
depending upon whether the tracker has been initialised or not. The other two
may be done at any time, before or after tracker initialisation. Yes, this
includes adding or removing properties from classes.


Trackers in a Nutshell
======================

Trackers have the following structure:

=================== ========================================================
Tracker File        Description
=================== ========================================================
config.py           Holds the basic `tracker configuration`_                 
dbinit.py           Holds the `tracker schema`_                              
interfaces.py       Defines the Web and E-Mail interfaces for the tracker    
select_db.py        Selects the database back-end for the tracker            
db/                 Holds the tracker's database                             
db/files/           Holds the tracker's upload files and messages            
detectors/          Auditors and reactors for this tracker                   
html/               Web interface templates, images and style sheets         
=================== ======================================================== 

Tracker Configuration
=====================

The ``config.py`` located in your tracker home contains the basic
configuration for the web and e-mail components of roundup's interfaces.
As the name suggests, this file is a Python module. This means that any
valid python expression may be used in the file. Mostly though, you'll
be setting the configuration variables to string values. Python string
values must be quoted with either single or double quotes::

   'this is a string'
   "this is also a string - use it when the value has 'single quotes'"
   this is not a string - it's not quoted

Python strings may use formatting that's almost identical to C string
formatting. The ``%`` operator is used to perform the formatting, like
so::

    'roundup-admin@%s'%MAIL_DOMAIN

this will create a string ``'roundup-admin@tracker.domain.example'`` if
MAIL_DOMAIN is set to ``'tracker.domain.example'``.

You'll also note some values are set to::

   os.path.join(TRACKER_HOME, 'db')

or similar. This creates a new string which holds the path to the
``'db'`` directory in the TRACKER_HOME directory. This is just a
convenience so if the TRACKER_HOME changes you don't have to edit
multiple valoues.

The configuration variables available are:

**TRACKER_HOME** - ``os.path.split(__file__)[0]``
 The tracker home directory. The above default code will automatically
 determine the tracker home for you, so you can just leave it alone.

**MAILHOST** - ``'localhost'``
 The SMTP mail host that roundup will use to send e-mail.

**MAILUSER** - ``()``
 If your SMTP mail host requires a username and password for access, then
 specify them here. eg. ``MAILUSER = ('username', 'password')``

**MAILHOST_TLS** - ``'no'``
 If your SMTP mail host provides or requires TLS (Transport Layer
 Security) then set ``MAILHOST_TLS = 'yes'``

**MAILHOST_TLS_KEYFILE** - ``''``
 If you're using TLS, you may also set MAILHOST_TLS_KEYFILE to the name of
 a PEM formatted file that contains your private key.

**MAILHOST_TLS_CERTFILE** - ``''``
 If you're using TLS and have specified a MAILHOST_TLS_KEYFILE, you may
 also set MAILHOST_TLS_CERTFILE to the name of a PEM formatted certificate
 chain file.

**MAIL_DOMAIN** - ``'tracker.domain.example'``
 The domain name used for email addresses.

**DATABASE** - ``os.path.join(TRACKER_HOME, 'db')``
 This is the directory that the database is going to be stored in. By default
 it is in the tracker home.

**TEMPLATES** - ``os.path.join(TRACKER_HOME, 'html')``
 This is the directory that the HTML templates reside in. By default they are
 in the tracker home.

**TRACKER_NAME** - ``'Roundup issue tracker'``
 A descriptive name for your roundup tracker. This is sent out in e-mails and
 appears in the heading of CGI pages.

**TRACKER_EMAIL** - ``'issue_tracker@%s'%MAIL_DOMAIN``
 The email address that e-mail sent to roundup should go to. Think of it as the
 tracker's personal e-mail address.

**TRACKER_WEB** - ``'http://tracker.example/cgi-bin/roundup.cgi/bugs/'``
 The web address that the tracker is viewable at. This will be included in
 information sent to users of the tracker. The URL **must** include the
 cgi-bin part or anything else that is required to get to the home page of
 the tracker. You **must** include a trailing '/' in the URL.

**ADMIN_EMAIL** - ``'roundup-admin@%s'%MAIL_DOMAIN``
 The email address that roundup will complain to if it runs into trouble.

**EMAIL_FROM_TAG** - ``''``
 Additional text to include in the "name" part of the ``From:`` address used
 in nosy messages. If the sending user is "Foo Bar", the ``From:`` line is
 usually::

    "Foo Bar" <issue_tracker@tracker.example>

 The EMAIL_FROM_TAG goes inside the "Foo Bar" quotes like so::

    "Foo Bar EMAIL_FROM_TAG" <issue_tracker@tracker.example>

**MESSAGES_TO_AUTHOR** - ``'new'``, ``'yes'`` or``'no'``
 Send nosy messages to the author of the message?
 If 'new' is used, then the author will only be sent the message when the
 message creates a new issue. If 'yes' then the author will always be sent
 a copy of the message they wrote.

**ADD_AUTHOR_TO_NOSY** - ``'new'``, ``'yes'`` or ``'no'``
 Does the author of a message get placed on the nosy list automatically?
 If ``'new'`` is used, then the author will only be added when a message
 creates a new issue. If ``'yes'``, then the author will be added on followups
 too. If ``'no'``, they're never added to the nosy.

**ADD_RECIPIENTS_TO_NOSY** - ``'new'``, ``'yes'`` or ``'no'``
 Do the recipients (To:, Cc:) of a message get placed on the nosy list?
 If ``'new'`` is used, then the recipients will only be added when a message
 creates a new issue. If ``'yes'``, then the recipients will be added on
 followups too. If ``'no'``, they're never added to the nosy.

**EMAIL_SIGNATURE_POSITION** - ``'top'``, ``'bottom'`` or ``'none'``
 Where to place the email signature in messages that Roundup generates.

**EMAIL_KEEP_QUOTED_TEXT** - ``'yes'`` or ``'no'``
 Keep email citations. Citations are the part of e-mail which the sender has
 quoted in their reply to previous e-mail.

**EMAIL_LEAVE_BODY_UNCHANGED** - ``'no'``
 Preserve the email body as is. Enabiling this will cause the entire message
 body to be stored, including all citations and signatures. It should be
 either ``'yes'`` or ``'no'``.

**MAIL_DEFAULT_CLASS** - ``'issue'`` or ``''``
 Default class to use in the mailgw if one isn't supplied in email
 subjects. To disable, comment out the variable below or leave it blank.

The default config.py is given below - as you
can see, the MAIL_DOMAIN must be edited before any interaction with the
tracker is attempted.::

    # roundup home is this package's directory
    TRACKER_HOME=os.path.split(__file__)[0]

    # The SMTP mail host that roundup will use to send mail
    MAILHOST = 'localhost'

    # The domain name used for email addresses.
    MAIL_DOMAIN = 'your.tracker.email.domain.example'

    # This is the directory that the database is going to be stored in
    DATABASE = os.path.join(TRACKER_HOME, 'db')

    # This is the directory that the HTML templates reside in
    TEMPLATES = os.path.join(TRACKER_HOME, 'html')

    # A descriptive name for your roundup tracker
    TRACKER_NAME = 'Roundup issue tracker'

    # The email address that mail to roundup should go to
    TRACKER_EMAIL = 'issue_tracker@%s'%MAIL_DOMAIN

    # The web address that the tracker is viewable at. This will be
    # included in information sent to users of the tracker. The URL MUST
    # include the cgi-bin part or anything else that is required to get
    # to the home page of the tracker. You MUST include a trailing '/'
    # in the URL.
    TRACKER_WEB = 'http://tracker.example/cgi-bin/roundup.cgi/bugs/'

    # The email address that roundup will complain to if it runs into
    # trouble
    ADMIN_EMAIL = 'roundup-admin@%s'%MAIL_DOMAIN

    # Additional text to include in the "name" part of the From: address
    # used in nosy messages. If the sending user is "Foo Bar", the From:
    # line is usually: "Foo Bar" <issue_tracker@tracker.example>
    # the EMAIL_FROM_TAG goes inside the "Foo Bar" quotes like so:
    #    "Foo Bar EMAIL_FROM_TAG" <issue_tracker@tracker.example>
    EMAIL_FROM_TAG = ""

    # Send nosy messages to the author of the message
    MESSAGES_TO_AUTHOR = 'no'           # either 'yes' or 'no'

    # Does the author of a message get placed on the nosy list
    # automatically? If 'new' is used, then the author will only be
    # added when a message creates a new issue. If 'yes', then the
    # author will be added on followups too. If 'no', they're never
    # added to the nosy.
    ADD_AUTHOR_TO_NOSY = 'new'          # one of 'yes', 'no', 'new'

    # Do the recipients (To:, Cc:) of a message get placed on the nosy
    # list? If 'new' is used, then the recipients will only be added
    # when a message creates a new issue. If 'yes', then the recipients
    # will be added on followups too. If 'no', they're never added to
    # the nosy.
    ADD_RECIPIENTS_TO_NOSY = 'new'      # either 'yes', 'no', 'new'

    # Where to place the email signature
    EMAIL_SIGNATURE_POSITION = 'bottom' # one of 'top', 'bottom', 'none'

    # Keep email citations
    EMAIL_KEEP_QUOTED_TEXT = 'no'       # either 'yes' or 'no'

    # Preserve the email body as is
    EMAIL_LEAVE_BODY_UNCHANGED = 'no'   # either 'yes' or 'no'

    # Default class to use in the mailgw if one isn't supplied in email
    # subjects. To disable, comment out the variable below or leave it
    # blank. Examples:
    MAIL_DEFAULT_CLASS = 'issue'   # use "issue" class by default
    #MAIL_DEFAULT_CLASS = ''        # disable (or just comment the var out)

    # 
    # SECURITY DEFINITIONS
    #
    # define the Roles that a user gets when they register with the
    # tracker these are a comma-separated string of role names (e.g.
    # 'Admin,User')
    NEW_WEB_USER_ROLES = 'User'
    NEW_EMAIL_USER_ROLES = 'User'

Tracker Schema
==============

Note: if you modify the schema, you'll most likely need to edit the
      `web interface`_ HTML template files and `detectors`_ to reflect
      your changes.

A tracker schema defines what data is stored in the tracker's database.
Schemas are defined using Python code in the ``dbinit.py`` module of your
tracker. The "classic" schema looks like this (see below for the meaning
of ``'setkey'``)::

    pri = Class(db, "priority", name=String(), order=String())
    pri.setkey("name")

    stat = Class(db, "status", name=String(), order=String())
    stat.setkey("name")

    keyword = Class(db, "keyword", name=String())
    keyword.setkey("name")

    user = Class(db, "user", username=String(), organisation=String(),
        password=String(), address=String(), realname=String(),
        phone=String())
    user.setkey("username")

    msg = FileClass(db, "msg", author=Link("user"), summary=String(),
        date=Date(), recipients=Multilink("user"),
        files=Multilink("file"))

    file = FileClass(db, "file", name=String(), type=String())

    issue = IssueClass(db, "issue", topic=Multilink("keyword"),
        status=Link("status"), assignedto=Link("user"),
        priority=Link("priority"))
    issue.setkey('title')

Classes and Properties - creating a new information store
---------------------------------------------------------

In the tracker above, we've defined 7 classes of information:

  priority
      Defines the possible levels of urgency for issues.

  status
      Defines the possible states of processing the issue may be in.

  keyword
      Initially empty, will hold keywords useful for searching issues.

  user
      Initially holding the "admin" user, will eventually have an entry
      for all users using roundup.

  msg
      Initially empty, will hold all e-mail messages sent to or
      generated by roundup.

  file
      Initially empty, will hold all files attached to issues.

  issue
      Initially empty, this is where the issue information is stored.

We define the "priority" and "status" classes to allow two things:
reduction in the amount of information stored on the issue and more
powerful, accurate searching of issues by priority and status. By only
requiring a link on the issue (which is stored as a single number) we
reduce the chance that someone mis-types a priority or status - or
simply makes a new one up.


Class and Items
~~~~~~~~~~~~~~~

A Class defines a particular class (or type) of data that will be stored
in the database. A class comprises one or more properties, which gives
the information about the class items.

The actual data entered into the database, using ``class.create()``, are
called items. They have a special immutable property called ``'id'``. We
sometimes refer to this as the *itemid*.


Properties
~~~~~~~~~~

A Class is comprised of one or more properties of the following types:

* String properties are for storing arbitrary-length strings.
* Password properties are for storing encoded arbitrary-length strings.
  The default encoding is defined on the ``roundup.password.Password``
  class.
* Date properties store date-and-time stamps. Their values are Timestamp
  objects.
* Number properties store numeric values.
* Boolean properties store on/off, yes/no, true/false values.
* A Link property refers to a single other item selected from a
  specified class. The class is part of the property; the value is an
  integer, the id of the chosen item.
* A Multilink property refers to possibly many items in a specified
  class. The value is a list of integers.


FileClass
~~~~~~~~~

FileClasses save their "content" attribute off in a separate file from
the rest of the database. This reduces the number of large entries in
the database, which generally makes databases more efficient, and also
allows us to use command-line tools to operate on the files. They are
stored in the files sub-directory of the ``'db'`` directory in your
tracker.


IssueClass
~~~~~~~~~~

IssueClasses automatically include the "messages", "files", "nosy", and
"superseder" properties.

The messages and files properties list the links to the messages and
files related to the issue. The nosy property is a list of links to
users who wish to be informed of changes to the issue - they get "CC'ed"
e-mails when messages are sent to or generated by the issue. The nosy
reactor (in the ``'detectors'`` directory) handles this action. The
superseder link indicates an issue which has superseded this one.

They also have the dynamically generated "creation", "activity" and
"creator" properties.

The value of the "creation" property is the date when an item was
created, and the value of the "activity" property is the date when any
property on the item was last edited (equivalently, these are the dates
on the first and last records in the item's journal). The "creator"
property holds a link to the user that created the issue.


setkey(property)
~~~~~~~~~~~~~~~~

Select a String property of the class to be the key property. The key
property must be unique, and allows references to the items in the class
by the content of the key property. That is, we can refer to users by
their username: for example, let's say that there's an issue in roundup,
issue 23. There's also a user, richard, who happens to be user 2. To
assign an issue to him, we could do either of::

     roundup-admin set issue23 assignedto=2

or::

     roundup-admin set issue23 assignedto=richard

Note, the same thing can be done in the web and e-mail interfaces. 

If a class does not have an "order" property, the key is also used to
sort instances of the class when it is rendered in the user interface.
(If a class has no "order" property, sorting is by the labelproperty of
the class. This is computed, in order of precedence, as the key, the
"name", the "title", or the first property alphabetically.)


create(information)
~~~~~~~~~~~~~~~~~~~

Create an item in the database. This is generally used to create items
in the "definitional" classes like "priority" and "status".


Examples of adding to your schema
---------------------------------

TODO


Detectors - adding behaviour to your tracker
============================================
.. _detectors:

Detectors are initialised every time you open your tracker database, so
you're free to add and remove them any time, even after the database is
initialised via the "roundup-admin initialise" command.

The detectors in your tracker fire *before* (**auditors**) and *after*
(**reactors**) changes to the contents of your database. They are Python
modules that sit in your tracker's ``detectors`` directory. You will
have some installed by default - have a look. You can write new
detectors or modify the existing ones. The existing detectors installed
for you are:

**nosyreaction.py**
  This provides the automatic nosy list maintenance and email sending.
  The nosy reactor (``nosyreaction``) fires when new messages are added
  to issues. The nosy auditor (``updatenosy``) fires when issues are
  changed, and figures out what changes need to be made to the nosy list
  (such as adding new authors, etc.)
**statusauditor.py**
  This provides the ``chatty`` auditor which changes the issue status
  from ``unread`` or ``closed`` to ``chatting`` if new messages appear.
  It also provides the ``presetunread`` auditor which pre-sets the
  status to ``unread`` on new items if the status isn't explicitly
  defined.
**messagesummary.py**
  Generates the ``summary`` property for new messages based on the message
  content.
**userauditor.py**
  Verifies the content of some of the user fields (email addresses and
  roles lists).

If you don't want this default behaviour, you're completely free to change
or remove these detectors.

See the detectors section in the `design document`__ for details of the
interface for detectors.

__ design.html

Sample additional detectors that have been found useful will appear in
the ``'detectors'`` directory of the Roundup distribution. If you want
to use one, copy it to the ``'detectors'`` of your tracker instance:

**newissuecopy.py**
  This detector sends an email to a team address whenever a new issue is
  created. The address is hard-coded into the detector, so edit it
  before you use it (look for the text 'team@team.host') or you'll get
  email errors!

  The detector code::

    from roundup import roundupdb

    def newissuecopy(db, cl, nodeid, oldvalues):
        ''' Copy a message about new issues to a team address.
        '''
        # so use all the messages in the create
        change_note = cl.generateCreateNote(nodeid)

        # send a copy to the nosy list
        for msgid in cl.get(nodeid, 'messages'):
            try:
                # note: last arg must be a list
                cl.send_message(nodeid, msgid, change_note,
                    ['team@team.host'])
            except roundupdb.MessageSendError, message:
                raise roundupdb.DetectorError, message

    def init(db):
        db.issue.react('create', newissuecopy)


Database Content
================

Note: if you modify the content of definitional classes, you'll most
       likely need to edit the tracker `detectors`_ to reflect your
       changes.

Customisation of the special "definitional" classes (eg. status,
priority, resolution, ...) may be done either before or after the
tracker is initialised. The actual method of doing so is completely
different in each case though, so be careful to use the right one.

**Changing content before tracker initialisation**
    Edit the dbinit module in your tracker to alter the items created in
    using the ``create()`` methods.

**Changing content after tracker initialisation**
    As the "admin" user, click on the "class list" link in the web
    interface to bring up a list of all database classes. Click on the
    name of the class you wish to change the content of.

    You may also use the ``roundup-admin`` interface's create, set and
    retire methods to add, alter or remove items from the classes in
    question.

See "`adding a new field to the classic schema`_" for an example that
requires database content changes.


Access Controls
===============

A set of Permissions is built into the security module by default:

- Edit (everything)
- View (everything)

The default interfaces define:

- Web Registration
- Web Access
- Web Roles
- Email Registration
- Email Access

These are hooked into the default Roles:

- Admin (Edit everything, View everything, Web Roles)
- User (Web Access, Email Access)
- Anonymous (Web Registration, Email Registration)

And finally, the "admin" user gets the "Admin" Role, and the "anonymous"
user gets "Anonymous" assigned when the database is initialised on
installation. The two default schemas then define:

- Edit issue, View issue (both)
- Edit file, View file (both)
- Edit msg, View msg (both)
- Edit support, View support (extended only)

and assign those Permissions to the "User" Role. Put together, these
settings appear in the ``open()`` function of the tracker ``dbinit.py``
(the following is taken from the "minimal" template's ``dbinit.py``)::

    #
    # SECURITY SETTINGS
    #
    # new permissions for this schema
    for cl in ('user', ):
        db.security.addPermission(name="Edit", klass=cl,
            description="User is allowed to edit "+cl)
        db.security.addPermission(name="View", klass=cl,
            description="User is allowed to access "+cl)

    # and give the regular users access to the web and email interface
    p = db.security.getPermission('Web Access')
    db.security.addPermissionToRole('User', p)
    p = db.security.getPermission('Email Access')
    db.security.addPermissionToRole('User', p)

    # May users view other user information? Comment these lines out
    # if you don't want them to
    p = db.security.getPermission('View', 'user')
    db.security.addPermissionToRole('User', p)

    # Assign the appropriate permissions to the anonymous user's
    # Anonymous role. Choices here are:
    # - Allow anonymous users to register through the web
    p = db.security.getPermission('Web Registration')
    db.security.addPermissionToRole('Anonymous', p)
    # - Allow anonymous (new) users to register through the email
    #   gateway
    p = db.security.getPermission('Email Registration')
    db.security.addPermissionToRole('Anonymous', p)


New User Roles
--------------

New users are assigned the Roles defined in the config file as:

- NEW_WEB_USER_ROLES
- NEW_EMAIL_USER_ROLES


Changing Access Controls
------------------------

You may alter the configuration variables to change the Role that new
web or email users get, for example to not give them access to the web
interface if they register through email. 

You may use the ``roundup-admin`` "``security``" command to display the
current Role and Permission configuration in your tracker.


Adding a new Permission
~~~~~~~~~~~~~~~~~~~~~~~

When adding a new Permission, you will need to:

1. add it to your tracker's dbinit so it is created
2. enable it for the Roles that should have it (verify with
   "``roundup-admin security``")
3. add it to the relevant HTML interface templates
4. add it to the appropriate xxxPermission methods on in your tracker
   interfaces module


Example Scenarios
~~~~~~~~~~~~~~~~~

**automatic registration of users in the e-mail gateway**
 By giving the "anonymous" user the "Email Registration" Role, any
 unidentified user will automatically be registered with the tracker
 (with no password, so they won't be able to log in through the web
 until an admin sets their password). Note: this is the default
 behaviour in the tracker templates that ship with Roundup.

**anonymous access through the e-mail gateway**
 Give the "anonymous" user the "Email Access" and ("Edit", "issue")
 Roles but do not not give them the "Email Registration" Role. This
 means that when an unknown user sends email into the tracker, they're
 automatically logged in as "anonymous". Since they don't have the
 "Email Registration" Role, they won't be automatically registered, but
 since "anonymous" has permission to use the gateway, they'll still be
 able to submit issues. Note that the Sender information - their email
 address - will not be available - they're *anonymous*.

**only developers may be assigned issues**
 Create a new Permission called "Fixer" for the "issue" class. Create a
 new Role "Developer" which has that Permission, and assign that to the
 appropriate users. Filter the list of users available in the assignedto
 list to include only those users. Enforce the Permission with an
 auditor. See the example 
 `restricting the list of users that are assignable to a task`_.

**only managers may sign off issues as complete**
 Create a new Permission called "Closer" for the "issue" class. Create a
 new Role "Manager" which has that Permission, and assign that to the
 appropriate users. In your web interface, only display the "resolved"
 issue state option when the user has the "Closer" Permissions. Enforce
 the Permission with an auditor. This is very similar to the previous
 example, except that the web interface check would look like::

   <option tal:condition="python:request.user.hasPermission('Closer')"
           value="resolved">Resolved</option>
 
**don't give web access to users who register through email**
 Create a new Role called "Email User" which has all the Permissions of
 the normal "User" Role minus the "Web Access" Permission. This will
 allow users to send in emails to the tracker, but not access the web
 interface.

**let some users edit the details of all users**
 Create a new Role called "User Admin" which has the Permission for
 editing users::

    db.security.addRole(name='User Admin', description='Managing users')
    p = db.security.getPermission('Edit', 'user')
    db.security.addPermissionToRole('User Admin', p)

 and assign the Role to the users who need the permission.


Web Interface
=============

.. contents::
   :local:
   :depth: 1

The web interface is provided by the ``roundup.cgi.client`` module and
is used by ``roundup.cgi``, ``roundup-server`` and ``ZRoundup``
(``ZRoundup``  is broken, until further notice). In all cases, we
determine which tracker is being accessed (the first part of the URL
path inside the scope of the CGI handler) and pass control on to the
tracker ``interfaces.Client`` class - which uses the ``Client`` class
from ``roundup.cgi.client`` - which handles the rest of the access
through its ``main()`` method. This means that you can do pretty much
anything you want as a web interface to your tracker.

Repercussions of changing the tracker schema
---------------------------------------------

If you choose to change the `tracker schema`_ you will need to ensure
the web interface knows about it:

1. Index, item and search pages for the relevant classes may need to
   have properties added or removed,
2. The "page" template may require links to be changed, as might the
   "home" page's content arguments.

How requests are processed
--------------------------

The basic processing of a web request proceeds as follows:

1. figure out who we are, defaulting to the "anonymous" user
2. figure out what the request is for - we call this the "context"
3. handle any requested action (item edit, search, ...)
4. render the template requested by the context, resulting in HTML
   output

In some situations, exceptions occur:

- HTTP Redirect  (generally raised by an action)
- SendFile       (generally raised by ``determine_context``)
    here we serve up a FileClass "content" property
- SendStaticFile (generally raised by ``determine_context``)
    here we serve up a file from the tracker "html" directory
- Unauthorised   (generally raised by an action)
    here the action is cancelled, the request is rendered and an error
    message is displayed indicating that permission was not granted for
    the action to take place
- NotFound       (raised wherever it needs to be)
    this exception percolates up to the CGI interface that called the
    client

Determining web context
-----------------------

To determine the "context" of a request, we look at the URL and the
special request variable ``@template``. The URL path after the tracker
identifier is examined. Typical URL paths look like:

1.  ``/tracker/issue``
2.  ``/tracker/issue1``
3.  ``/tracker/_file/style.css``
4.  ``/cgi-bin/roundup.cgi/tracker/file1``
5.  ``/cgi-bin/roundup.cgi/tracker/file1/kitten.png``

where the "tracker identifier" is "tracker" in the above cases. That means
we're looking at "issue", "issue1", "_file/style.css", "file1" and
"file1/kitten.png" in the cases above. The path is generally only one
entry long - longer paths are handled differently.

a. if there is no path, then we are in the "home" context.
b. if the path starts with "_file" (as in example 3,
   "/tracker/_file/style.css"), then the additional path entry,
   "style.css" specifies the filename of a static file we're to serve up
   from the tracker "html" directory. Raises a SendStaticFile exception.
c. if there is something in the path (as in example 1, "issue"), it
   identifies the tracker class we're to display.
d. if the path is an item designator (as in examples 2 and 4, "issue1"
   and "file1"), then we're to display a specific item.
e. if the path starts with an item designator and is longer than one
   entry (as in example 5, "file1/kitten.png"), then we're assumed to be
   handling an item of a ``FileClass``, and the extra path information
   gives the filename that the client is going to label the download
   with (i.e. "file1/kitten.png" is nicer to download than "file1").
   This raises a ``SendFile`` exception.

Both b. and e. stop before we bother to determine the template we're
going to use. That's because they don't actually use templates.

The template used is specified by the ``@template`` CGI variable, which
defaults to:

- only classname suplied:        "index"
- full item designator supplied: "item"


Performing actions in web requests
----------------------------------

When a user requests a web page, they may optionally also request for an
action to take place. As described in `how requests are processed`_, the
action is performed before the requested page is generated. Actions are
triggered by using a ``@action`` CGI variable, where the value is one
of:

**login**
 Attempt to log a user in.

**logout**
 Log the user out - make them "anonymous".

**register**
 Attempt to create a new user based on the contents of the form and then
 log them in.

**edit**
 Perform an edit of an item in the database. There are some `special form
 variables`_ you may use.

**new**
 Add a new item to the database. You may use the same `special form
 variables`_ as in the "edit" action.

**retire**
 Retire the item in the database.

**editCSV**
 Performs an edit of all of a class' items in one go. See also the
 *class*.csv templating method which generates the CSV data to be
 edited, and the ``'_generic.index'`` template which uses both of these
 features.

**search**
 Mangle some of the form variables:

 - Set the form ":filter" variable based on the values of the filter
   variables - if they're set to anything other than "dontcare" then add
   them to :filter.

 - Also handle the ":queryname" variable and save off the query to the
   user's query list.

Each of the actions is implemented by a corresponding ``*actionAction*``
(where "action" is the name of the action) method on the
``roundup.cgi.Client`` class, which also happens to be available in your
tracker instance as ``interfaces.Client``. So if you need to define new
actions, you may add them there (see `defining new web actions`_).

Each action also has a corresponding ``*actionPermission*`` (where
"action" is the name of the action) method which determines whether the
action is permissible given the current user. The base permission checks
are:

**login**
 Determine whether the user has permission to log in. Base behaviour is
 to check the user has "Web Access".
**logout**
 No permission checks are made.
**register**
 Determine whether the user has permission to register. Base behaviour
 is to check the user has the "Web Registration" Permission.
**edit**
 Determine whether the user has permission to edit this item. Base
 behaviour is to check whether the user can edit this class. If we're
 editing the "user" class, users are allowed to edit their own details -
 unless they try to edit the "roles" property, which requires the
 special Permission "Web Roles".
**new**
 Determine whether the user has permission to create (or edit) this
 item. Base behaviour is to check the user can edit this class. No
 additional property checks are made. Additionally, new user items may
 be created if the user has the "Web Registration" Permission.
**editCSV**
 Determine whether the user has permission to edit this class. Base
 behaviour is to check whether the user may edit this class.
**search**
 Determine whether the user has permission to search this class. Base
 behaviour is to check whether the user may view this class.


Special form variables
----------------------

Item properties and their values are edited with html FORM
variables and their values. You can:

- Change the value of some property of the current item.
- Create a new item of any class, and edit the new item's
  properties,
- Attach newly created items to a multilink property of the
  current item.
- Remove items from a multilink property of the current item.
- Specify that some properties are required for the edit
  operation to be successful.

In the following, <bracketed> values are variable, "@" may be
either ":" or "@", and other text "required" is fixed.

Most properties are specified as form variables:

``<propname>``
  property on the current context item

``<designator>"@"<propname>``
  property on the indicated item (for editing related information)

Designators name a specific item of a class.

``<classname><N>``
    Name an existing item of class <classname>.

``<classname>"-"<N>``
    Name the <N>th new item of class <classname>. If the form
    submission is successful, a new item of <classname> is
    created. Within the submitted form, a particular
    designator of this form always refers to the same new
    item.

Once we have determined the "propname", we look at it to see
if it's special:

``@required``
    The associated form value is a comma-separated list of
    property names that must be specified when the form is
    submitted for the edit operation to succeed.  

    When the <designator> is missing, the properties are
    for the current context item.  When <designator> is
    present, they are for the item specified by
    <designator>.

    The "@required" specifier must come before any of the
    properties it refers to are assigned in the form.

``@remove@<propname>=id(s)`` or ``@add@<propname>=id(s)``
    The "@add@" and "@remove@" edit actions apply only to
    Multilink properties.  The form value must be a
    comma-separate list of keys for the class specified by
    the simple form variable.  The listed items are added
    to (respectively, removed from) the specified
    property.

``@link@<propname>=<designator>``
    If the edit action is "@link@", the simple form
    variable must specify a Link or Multilink property.
    The form value is a comma-separated list of
    designators.  The item corresponding to each
    designator is linked to the property given by simple
    form variable.

None of the above (ie. just a simple form value)
    The value of the form variable is converted
    appropriately, depending on the type of the property.

    For a Link('klass') property, the form value is a
    single key for 'klass', where the key field is
    specified in dbinit.py.  

    For a Multilink('klass') property, the form value is a
    comma-separated list of keys for 'klass', where the
    key field is specified in dbinit.py.  

    Note that for simple-form-variables specifiying Link
    and Multilink properties, the linked-to class must
    have a key field.

    For a String() property specifying a filename, the
    file named by the form value is uploaded. This means we
    try to set additional properties "filename" and "type" (if
    they are valid for the class).  Otherwise, the property
    is set to the form value.

    For Date(), Interval(), Boolean(), and Number()
    properties, the form value is converted to the
    appropriate

Any of the form variables may be prefixed with a classname or
designator.

Two special form values are supported for backwards compatibility:

@note
    This is equivalent to::

        @link@messages=msg-1
        @msg-1@content=value

    except that in addition, the "author" and "date" properties of
    "msg-1" are set to the userid of the submitter, and the current
    time, respectively.

@file
    This is equivalent to::

        @link@files=file-1
        @file-1@content=value

    The String content value is handled as described above for file
    uploads.

If both the "@note" and "@file" form variables are
specified, the action::

        @link@msg-1@files=file-1

is also performed.

We also check that FileClass items have a "content" property with
actual content, otherwise we remove them from all_props before
returning.



Default templates
-----------------

Most customisation of the web view can be done by modifying the
templates in the tracker ``'html'`` directory. There are several types
of files in there. The *minimal* template includes:

**page.html**
  This template usually defines the overall look of your tracker. When
  you view an issue, it appears inside this template. When you view an
  index, it also appears inside this template. This template defines a
  macro called "icing" which is used by almost all other templates as a
  coating for their content, using its "content" slot. It also defines
  the "head_title" and "body_title" slots to allow setting of the page
  title.
**home.html**
  the default page displayed when no other page is indicated by the user
**home.classlist.html**
  a special version of the default page that lists the classes in the
  tracker
**classname.item.html**
  displays an item of the *classname* class
**classname.index.html**
  displays a list of *classname* items
**classname.search.html**
  displays a search page for *classname* items
**_generic.index.html**
  used to display a list of items where there is no
  ``*classname*.index`` available
**_generic.help.html**
  used to display a "class help" page where there is no
  ``*classname*.help``
**user.register.html**
  a special page just for the user class, that renders the registration
  page
**style.css.html**
  a static file that is served up as-is

The *classic* template has a number of additional templates.

Note: Remember that you can create any template extension you want to,
so if you just want to play around with the templating for new issues,
you can copy the current "issue.item" template to "issue.test", and then
access the test template using the "@template" URL argument::

   http://your.tracker.example/tracker/issue?@template=test

and it won't affect your users using the "issue.item" template.


How the templates work
----------------------


Basic Templating Actions
~~~~~~~~~~~~~~~~~~~~~~~~

Roundup's templates consist of special attributes on the HTML tags.
These attributes form the Template Attribute Language, or TAL. The basic
TAL commands are:

**tal:define="variable expression; variable expression; ..."**
   Define a new variable that is local to this tag and its contents. For
   example::

      <html tal:define="title request/description">
       <head><title tal:content="title"></title></head>
      </html>

   In this example, the variable "title" is defined as the result of the
   expression "request/description". The "tal:content" command inside the
   <html> tag may then use the "title" variable.

**tal:condition="expression"**
   Only keep this tag and its contents if the expression is true. For
   example::

     <p tal:condition="python:request.user.hasPermission('View', 'issue')">
      Display some issue information.
     </p>

   In the example, the <p> tag and its contents are only displayed if
   the user has the "View" permission for issues. We consider the number
   zero, a blank string, an empty list, and the built-in variable
   nothing to be false values. Nearly every other value is true,
   including non-zero numbers, and strings with anything in them (even
   spaces!).

**tal:repeat="variable expression"**
   Repeat this tag and its contents for each element of the sequence
   that the expression returns, defining a new local variable and a
   special "repeat" variable for each element. For example::

     <tr tal:repeat="u user/list">
      <td tal:content="u/id"></td>
      <td tal:content="u/username"></td>
      <td tal:content="u/realname"></td>
     </tr>

   The example would iterate over the sequence of users returned by
   "user/list" and define the local variable "u" for each entry.

**tal:replace="expression"**
   Replace this tag with the result of the expression. For example::

    <span tal:replace="request/user/realname" />

   The example would replace the <span> tag and its contents with the
   user's realname. If the user's realname was "Bruce", then the
   resultant output would be "Bruce".

**tal:content="expression"**
   Replace the contents of this tag with the result of the expression.
   For example::

    <span tal:content="request/user/realname">user's name appears here
    </span>

   The example would replace the contents of the <span> tag with the
   user's realname. If the user's realname was "Bruce" then the
   resultant output would be "<span>Bruce</span>".

**tal:attributes="attribute expression; attribute expression; ..."**
   Set attributes on this tag to the results of expressions. For
   example::

     <a tal:attributes="href string:user${request/user/id}">My Details</a>

   In the example, the "href" attribute of the <a> tag is set to the
   value of the "string:user${request/user/id}" expression, which will
   be something like "user123".

**tal:omit-tag="expression"**
   Remove this tag (but not its contents) if the expression is true. For
   example::

      <span tal:omit-tag="python:1">Hello, world!</span>

   would result in output of::

      Hello, world!

Note that the commands on a given tag are evaulated in the order above,
so *define* comes before *condition*, and so on.

Additionally, you may include tags such as <tal:block>, which are
removed from output. Its content is kept, but the tag itself is not (so
don't go using any "tal:attributes" commands on it). This is useful for
making arbitrary blocks of HTML conditional or repeatable (very handy
for repeating multiple table rows, which would othewise require an
illegal tag placement to effect the repeat).


Templating Expressions
~~~~~~~~~~~~~~~~~~~~~~

The expressions you may use in the attribute values may be one of the
following forms:

**Path Expressions** - eg. ``item/status/checklist``
   These are object attribute / item accesses. Roughly speaking, the
   path ``item/status/checklist`` is broken into parts ``item``,
   ``status`` and ``checklist``. The ``item`` part is the root of the
   expression. We then look for a ``status`` attribute on ``item``, or
   failing that, a ``status`` item (as in ``item['status']``). If that
   fails, the path expression fails. When we get to the end, the object
   we're left with is evaluated to get a string - if it is a method, it
   is called; if it is an object, it is stringified. Path expressions
   may have an optional ``path:`` prefix, but they are the default
   expression type, so it's not necessary.

   If an expression evaluates to ``default``, then the expression is
   "cancelled" - whatever HTML already exists in the template will
   remain (tag content in the case of ``tal:content``, attributes in the
   case of ``tal:attributes``).

   If an expression evaluates to ``nothing`` then the target of the
   expression is removed (tag content in the case of ``tal:content``,
   attributes in the case of ``tal:attributes`` and the tag itself in
   the case of ``tal:replace``).

   If an element in the path may not exist, then you can use the ``|``
   operator in the expression to provide an alternative. So, the
   expression ``request/form/foo/value | default`` would simply leave
   the current HTML in place if the "foo" form variable doesn't exist.

   You may use the python function ``path``, as in
   ``path("item/status")``, to embed path expressions in Python
   expressions.

**String Expressions** - eg. ``string:hello ${user/name}`` 
   These expressions are simple string interpolations - though they can
   be just plain strings with no interpolation if you want. The
   expression in the ``${ ... }`` is just a path expression as above.

**Python Expressions** - eg. ``python: 1+1`` 
   These expressions give the full power of Python. All the "root level"
   variables are available, so ``python:item.status.checklist()`` would
   be equivalent to ``item/status/checklist``, assuming that
   ``checklist`` is a method.

Modifiers:

**structure** - eg. ``structure python:msg.content.plain(hyperlink=1)``
   The result of expressions are normally *escaped* to be safe for HTML
   display (all "<", ">" and "&" are turned into special entities). The
   ``structure`` expression modifier turns off this escaping - the
   result of the expression is now assumed to be HTML, which is passed
   to the web browser for rendering.

**not:** - eg. ``not:python:1=1``
   This simply inverts the logical true/false value of another
   expression.


Template Macros
~~~~~~~~~~~~~~~

Macros are used in Roundup to save us from repeating the same common
page stuctures over and over. The most common (and probably only) macro
you'll use is the "icing" macro defined in the "page" template.

Macros are generated and used inside your templates using special
attributes similar to the `basic templating actions`_. In this case,
though, the attributes belong to the Macro Expansion Template Attribute
Language, or METAL. The macro commands are:

**metal:define-macro="macro name"**
  Define that the tag and its contents are now a macro that may be
  inserted into other templates using the *use-macro* command. For
  example::

    <html metal:define-macro="page">
     ...
    </html>

  defines a macro called "page" using the ``<html>`` tag and its
  contents. Once defined, macros are stored on the template they're
  defined on in the ``macros`` attribute. You can access them later on
  through the ``templates`` variable, eg. the most common
  ``templates/page/macros/icing`` to access the "page" macro of the
  "page" template.

**metal:use-macro="path expression"**
  Use a macro, which is identified by the path expression (see above).
  This will replace the current tag with the identified macro contents.
  For example::

   <tal:block metal:use-macro="templates/page/macros/icing">
    ...
   </tal:block>

   will replace the tag and its contents with the "page" macro of the
   "page" template.

**metal:define-slot="slot name"** and **metal:fill-slot="slot name"**
  To define *dynamic* parts of the macro, you define "slots" which may
  be filled when the macro is used with a *use-macro* command. For
  example, the ``templates/page/macros/icing`` macro defines a slot like
  so::

    <title metal:define-slot="head_title">title goes here</title>

  In your *use-macro* command, you may now use a *fill-slot* command
  like this::

    <title metal:fill-slot="head_title">My Title</title>

  where the tag that fills the slot completely replaces the one defined
  as the slot in the macro.

Note that you may not mix METAL and TAL commands on the same tag, but
TAL commands may be used freely inside METAL-using tags (so your
*fill-slots* tags may have all manner of TAL inside them).


Information available to templates
----------------------------------

Note: this is implemented by
``roundup.cgi.templating.RoundupPageTemplate``

The following variables are available to templates.

**context**
  The current context. This is either None, a `hyperdb class wrapper`_
  or a `hyperdb item wrapper`_
**request**
  Includes information about the current request, including:
   - the current index information (``filterspec``, ``filter`` args,
     ``properties``, etc) parsed out of the form. 
   - methods for easy filterspec link generation
   - *user*, the current user item as an HTMLItem instance
   - *form*
     The current CGI form information as a mapping of form argument name
     to value
**config**
  This variable holds all the values defined in the tracker config.py
  file (eg. TRACKER_NAME, etc.)
**db**
  The current database, used to access arbitrary database items.
**templates**
  Access to all the tracker templates by name. Used mainly in
  *use-macro* commands.
**utils**
  This variable makes available some utility functions like batching.
**nothing**
  This is a special variable - if an expression evaluates to this, then
  the tag (in the case of a ``tal:replace``), its contents (in the case
  of ``tal:content``) or some attributes (in the case of
  ``tal:attributes``) will not appear in the the output. So, for
  example::

    <span tal:attributes="class nothing">Hello, World!</span>

  would result in::

    <span>Hello, World!</span>

**default**
  Also a special variable - if an expression evaluates to this, then the
  existing HTML in the template will not be replaced or removed, it will
  remain. So::

    <span tal:replace="default">Hello, World!</span>

  would result in::

    <span>Hello, World!</span>


The context variable
~~~~~~~~~~~~~~~~~~~~

The *context* variable is one of three things based on the current
context (see `determining web context`_ for how we figure this out):

1. if we're looking at a "home" page, then it's None
2. if we're looking at a specific hyperdb class, it's a
   `hyperdb class wrapper`_.
3. if we're looking at a specific hyperdb item, it's a
   `hyperdb item wrapper`_.

If the context is not None, we can access the properties of the class or
item. The only real difference between cases 2 and 3 above are:

1. the properties may have a real value behind them, and this will
   appear if the property is displayed through ``context/property`` or
   ``context/property/field``.
2. the context's "id" property will be a false value in the second case,
   but a real, or true value in the third. Thus we can determine whether
   we're looking at a real item from the hyperdb by testing
   "context/id".

Hyperdb class wrapper
:::::::::::::::::::::

Note: this is implemented by the ``roundup.cgi.templating.HTMLClass``
class.

This wrapper object provides access to a hyperb class. It is used
primarily in both index view and new item views, but it's also usable
anywhere else that you wish to access information about a class, or the
items of a class, when you don't have a specific item of that class in
mind.

We allow access to properties. There will be no "id" property. The value
accessed through the property will be the current value of the same name
from the CGI form.

There are several methods available on these wrapper objects:

=========== =============================================================
Method      Description
=========== =============================================================
properties  return a `hyperdb property wrapper`_ for all of this class's
            properties.
list        lists all of the active (not retired) items in the class.
csv         return the items of this class as a chunk of CSV text.
propnames   lists the names of the properties of this class.
filter      lists of items from this class, filtered and sorted by the
            current *request* filterspec/filter/sort/group args
classhelp   display a link to a javascript popup containing this class'
            "help" template.
submit      generate a submit button (and action hidden element)
renderWith  render this class with the given template.
history     returns 'New node - no history' :)
is_edit_ok  is the user allowed to Edit the current class?
is_view_ok  is the user allowed to View the current class?
=========== =============================================================

Note that if you have a property of the same name as one of the above
methods, you'll need to access it using a python "item access"
expression. For example::

   python:context['list']

will access the "list" property, rather than the list method.


Hyperdb item wrapper
::::::::::::::::::::

Note: this is implemented by the ``roundup.cgi.templating.HTMLItem``
class.

This wrapper object provides access to a hyperb item.

We allow access to properties. There will be no "id" property. The value
accessed through the property will be the current value of the same name
from the CGI form.

There are several methods available on these wrapper objects:

=============== ========================================================
Method          Description
=============== ========================================================
submit          generate a submit button (and action hidden element)
journal         return the journal of the current item (**not
                implemented**)
history         render the journal of the current item as HTML
renderQueryForm specific to the "query" class - render the search form
                for the query
hasPermission   specific to the "user" class - determine whether the
                user has a Permission
is_edit_ok      is the user allowed to Edit the current item?
is_view_ok      is the user allowed to View the current item?
=============== ========================================================

Note that if you have a property of the same name as one of the above
methods, you'll need to access it using a python "item access"
expression. For example::

   python:context['journal']

will access the "journal" property, rather than the journal method.


Hyperdb property wrapper
::::::::::::::::::::::::

Note: this is implemented by subclasses of the
``roundup.cgi.templating.HTMLProperty`` class (``HTMLStringProperty``,
``HTMLNumberProperty``, and so on).

This wrapper object provides access to a single property of a class. Its
value may be either:

1. if accessed through a `hyperdb item wrapper`_, then it's a value from
   the hyperdb
2. if access through a `hyperdb class wrapper`_, then it's a value from
   the CGI form


The property wrapper has some useful attributes:

=============== ========================================================
Attribute       Description
=============== ========================================================
_name           the name of the property
_value          the value of the property if any - this is the actual
                value retrieved from the hyperdb for this property
=============== ========================================================

There are several methods available on these wrapper objects:

=========== ================================================================
Method      Description
=========== ================================================================
plain       render a "plain" representation of the property. This method
            may take two arguments:

            escape
             If true, escape the text so it is HTML safe (default: no). The
             reason this defaults to off is that text is usually escaped
             at a later stage by the TAL commands, unless the "structure"
             option is used in the template. The following ``tal:content``
             expressions are all equivalent::
 
              "structure python:msg.content.plain(escape=1)"
              "python:msg.content.plain()"
              "msg/content/plain"
              "msg/content"

             Usually you'll only want to use the escape option in a
             complex expression.

            hyperlink
             If true, turn URLs, email addresses and hyperdb item
             designators in the text into hyperlinks (default: no). Note
             that you'll need to use the "structure" TAL option if you
             want to use this ``tal:content`` expression::
  
              "structure python:msg.content.plain(hyperlink=1)"

             Note also that the text is automatically HTML-escaped before
             the hyperlinking transformation.
hyperlinked The same as msg.content.plain(hyperlink=1), but nicer::

              "structure msg/content/hyperlinked"

field       render an appropriate form edit field for the property - for
            most types this is a text entry box, but for Booleans it's a
            tri-state yes/no/neither selection.
stext       only on String properties - render the value of the property
            as StructuredText (requires the StructureText module to be
            installed separately)
multiline   only on String properties - render a multiline form edit
            field for the property
email       only on String properties - render the value of the property
            as an obscured email address
confirm     only on Password properties - render a second form edit field
            for the property, used for confirmation that the user typed
            the password correctly. Generates a field with name
            "name:confirm".
now         only on Date properties - return the current date as a new
            property
reldate     only on Date properties - render the interval between the date
            and now
local       only on Date properties - return this date as a new property
            with some timezone offset
pretty      only on Interval properties - render the interval in a pretty
            format (eg. "yesterday")
menu        only on Link and Multilink properties - render a form select
            list for this property
reverse     only on Multilink properties - produce a list of the linked
            items in reverse order
=========== ================================================================


The request variable
~~~~~~~~~~~~~~~~~~~~

Note: this is implemented by the ``roundup.cgi.templating.HTMLRequest``
class.

The request variable is packed with information about the current
request.

.. taken from ``roundup.cgi.templating.HTMLRequest`` docstring

=========== ============================================================
Variable    Holds
=========== ============================================================
form        the CGI form as a cgi.FieldStorage
env         the CGI environment variables
base        the base URL for this tracker
user        a HTMLUser instance for this user
classname   the current classname (possibly None)
template    the current template (suffix, also possibly None)
form        the current CGI form variables in a FieldStorage
=========== ============================================================

**Index page specific variables (indexing arguments)**

=========== ============================================================
Variable    Holds
=========== ============================================================
columns     dictionary of the columns to display in an index page
show        a convenience access to columns - request/show/colname will
            be true if the columns should be displayed, false otherwise
sort        index sort column (direction, column name)
group       index grouping property (direction, column name)
filter      properties to filter the index on
filterspec  values to filter the index on
search_text text to perform a full-text search on for an index
=========== ============================================================

There are several methods available on the request variable:

=============== ========================================================
Method          Description
=============== ========================================================
description     render a description of the request - handle for the
                page title
indexargs_form  render the current index args as form elements
indexargs_url   render the current index args as a URL
base_javascript render some javascript that is used by other components
                of the templating
batch           run the current index args through a filter and return a
                list of items (see `hyperdb item wrapper`_, and
                `batching`_)
=============== ========================================================

The form variable
:::::::::::::::::

The form variable is a bit special because it's actually a python
FieldStorage object. That means that you have two ways to access its
contents. For example, to look up the CGI form value for the variable
"name", use the path expression::

   request/form/name/value

or the python expression::

   python:request.form['name'].value

Note the "item" access used in the python case, and also note the
explicit "value" attribute we have to access. That's because the form
variables are stored as MiniFieldStorages. If there's more than one
"name" value in the form, then the above will break since
``request/form/name`` is actually a *list* of MiniFieldStorages. So it's
best to know beforehand what you're dealing with.


The db variable
~~~~~~~~~~~~~~~

Note: this is implemented by the ``roundup.cgi.templating.HTMLDatabase``
class.

Allows access to all hyperdb classes as attributes of this variable. If
you want access to the "user" class, for example, you would use::

  db/user
  python:db.user

Also, the current id of the current user is available as
``db.getuid()``. This isn't so useful in templates (where you have
``request/user``), but it can be useful in detectors or interfaces.

The access results in a `hyperdb class wrapper`_.


The templates variable
~~~~~~~~~~~~~~~~~~~~~~

Note: this is implemented by the ``roundup.cgi.templating.Templates``
class.

This variable doesn't have any useful methods defined. It supports being
used in expressions to access the templates, and consequently the
template macros. You may access the templates using the following path
expression::

   templates/name

or the python expression::

   templates[name]

where "name" is the name of the template you wish to access. The
template has one useful attribute, namely "macros". To access a specific
macro (called "macro_name"), use the path expression::

   templates/name/macros/macro_name

or the python expression::

   templates[name].macros[macro_name]


The utils variable
~~~~~~~~~~~~~~~~~~

Note: this is implemented by the
``roundup.cgi.templating.TemplatingUtils`` class, but it may be extended
as described below.

=============== ========================================================
Method          Description
=============== ========================================================
Batch           return a batch object using the supplied list
=============== ========================================================

You may add additional utility methods by writing them in your tracker
``interfaces.py`` module's ``TemplatingUtils`` class. See `adding a time
log to your issues`_ for an example. The TemplatingUtils class itself
will have a single attribute, ``client``, which may be used to access
the ``client.db`` when you need to perform arbitrary database queries.

Batching
::::::::

Use Batch to turn a list of items, or item ids of a given class, into a
series of batches. Its usage is::

    python:utils.Batch(sequence, size, start, end=0, orphan=0,
    overlap=0)

or, to get the current index batch::

    request/batch

The parameters are:

========= ==============================================================
Parameter  Usage
========= ==============================================================
sequence  a list of HTMLItems
size      how big to make the sequence.
start     where to start (0-indexed) in the sequence.
end       where to end (0-indexed) in the sequence.
orphan    if the next batch would contain less items than this value,
          then it is combined with this batch
overlap   the number of items shared between adjacent batches
========= ==============================================================

All of the parameters are assigned as attributes on the batch object. In
addition, it has several more attributes:

=============== ========================================================
Attribute       Description
=============== ========================================================
start           indicates the start index of the batch. *Note: unlike
                the argument, is a 1-based index (I know, lame)*
first           indicates the start index of the batch *as a 0-based
                index*
length          the actual number of elements in the batch
sequence_length the length of the original, unbatched, sequence.
=============== ========================================================

And several methods:

=============== ========================================================
Method          Description
=============== ========================================================
previous        returns a new Batch with the previous batch settings
next            returns a new Batch with the next batch settings
propchanged     detect if the named property changed on the current item
                when compared to the last item
=============== ========================================================

An example of batching::

 <table class="otherinfo">
  <tr><th colspan="4" class="header">Existing Keywords</th></tr>
  <tr tal:define="keywords db/keyword/list"
      tal:repeat="start python:range(0, len(keywords), 4)">
   <td tal:define="batch python:utils.Batch(keywords, 4, start)"
       tal:repeat="keyword batch" tal:content="keyword/name">
       keyword here</td>
  </tr>
 </table>

... which will produce a table with four columns containing the items of
the "keyword" class (well, their "name" anyway).

Displaying Properties
---------------------

Properties appear in the user interface in three contexts: in indices,
in editors, and as search arguments. For each type of property, there
are several display possibilities. For example, in an index view, a
string property may just be printed as a plain string, but in an editor
view, that property may be displayed in an editable field.


Index Views
-----------

This is one of the class context views. It is also the default view for
classes. The template used is "*classname*.index".


Index View Specifiers
~~~~~~~~~~~~~~~~~~~~~

An index view specifier (URL fragment) looks like this (whitespace has
been added for clarity)::

     /issue?status=unread,in-progress,resolved&
            topic=security,ui&
            :group=+priority&
            :sort==activity&
            :filters=status,topic&
            :columns=title,status,fixer

The index view is determined by two parts of the specifier: the layout
part and the filter part. The layout part consists of the query
parameters that begin with colons, and it determines the way that the
properties of selected items are displayed. The filter part consists of
all the other query parameters, and it determines the criteria by which
items are selected for display. The filter part is interactively
manipulated with the form widgets displayed in the filter section. The
layout part is interactively manipulated by clicking on the column
headings in the table.

The filter part selects the union of the sets of items with values
matching any specified Link properties and the intersection of the sets
of items with values matching any specified Multilink properties.

The example specifies an index of "issue" items. Only items with a
"status" of either "unread" or "in-progress" or "resolved" are
displayed, and only items with "topic" values including both "security"
and "ui" are displayed. The items are grouped by priority, arranged in
ascending order; and within groups, sorted by activity, arranged in
descending order. The filter section shows filters for the "status" and
"topic" properties, and the table includes columns for the "title",
"status", and "fixer" properties.

Searching Views
---------------

Note: if you add a new column to the ``:columns`` form variable
      potentials then you will need to add the column to the appropriate
      `index views`_ template so that it is actually displayed.

This is one of the class context views. The template used is typically
"*classname*.search". The form on this page should have "search" as its
``@action`` variable. The "search" action:

- sets up additional filtering, as well as performing indexed text
  searching
- sets the ``:filter`` variable correctly
- saves the query off if ``:query_name`` is set.

The search page should lay out any fields that you wish to allow the
user to search on. If your schema contains a large number of properties,
you should be wary of making all of those properties available for
searching, as this can cause confusion. If the additional properties are
Strings, consider having their value indexed, and then they will be
searchable using the full text indexed search. This is both faster, and
more useful for the end user.

The two special form values on search pages which are handled by the
"search" action are:

:search_text
  Text with which to perform a search of the text index. Results from
  that search will be used to limit the results of other filters (using
  an intersection operation)
:query_name
  If supplied, the search parameters (including :search_text) will be
  saved off as a the query item and registered against the user's
  queries property. Note that the *classic* template schema has this
  ability, but the *minimal* template schema does not.


Item Views
----------

The basic view of a hyperdb item is provided by the "*classname*.item"
template. It generally has three sections; an "editor", a "spool" and a
"history" section.


Editor Section
~~~~~~~~~~~~~~

The editor section is used to manipulate the item - it may be a static
display if the user doesn't have permission to edit the item.

Here's an example of a basic editor template (this is the default
"classic" template issue item edit form - from the "issue.item.html"
template)::

 <table class="form">
 <tr>
  <th nowrap>Title</th>
  <td colspan="3" tal:content="structure python:context.title.field(size=60)">title</td>
 </tr>
 
 <tr>
  <th nowrap>Priority</th>
  <td tal:content="structure context/priority/menu">priority</td>
  <th nowrap>Status</th>
  <td tal:content="structure context/status/menu">status</td>
 </tr>
 
 <tr>
  <th nowrap>Superseder</th>
  <td>
   <span tal:replace="structure python:context.superseder.field(showid=1, size=20)" />
   <span tal:replace="structure python:db.issue.classhelp('id,title')" />
   <span tal:condition="context/superseder">
    <br>View: <span tal:replace="structure python:context.superseder.link(showid=1)" />
   </span>
  </td>
  <th nowrap>Nosy List</th>
  <td>
   <span tal:replace="structure context/nosy/field" />
   <span tal:replace="structure python:db.user.classhelp('username,realname,address,phone')" />
  </td>
 </tr>
 
 <tr>
  <th nowrap>Assigned To</th>
  <td tal:content="structure context/assignedto/menu">
   assignedto menu
  </td>
  <td>&nbsp;</td>
  <td>&nbsp;</td>
 </tr>
 
 <tr>
  <th nowrap>Change Note</th>
  <td colspan="3">
   <textarea name=":note" wrap="hard" rows="5" cols="60"></textarea>
  </td>
 </tr>
 
 <tr>
  <th nowrap>File</th>
  <td colspan="3"><input type="file" name=":file" size="40"></td>
 </tr>
 
 <tr>
  <td>&nbsp;</td>
  <td colspan="3" tal:content="structure context/submit">
   submit button will go here
  </td>
 </tr>
 </table>


When a change is submitted, the system automatically generates a message
describing the changed properties. As shown in the example, the editor
template can use the ":note" and ":file" fields, which are added to the
standard changenote message generated by Roundup.


Form values
:::::::::::

We have a number of ways to pull properties out of the form in order to
meet the various needs of:

1. editing the current item (perhaps an issue item)
2. editing information related to the current item (eg. messages or
   attached files)
3. creating new information to be linked to the current item (eg. time
   spent on an issue)

In the following, ``<bracketed>`` values are variable, ":" may be one of
":" or "@", and other text ("required") is fixed.

Properties are specified as form variables:

``<propname>``
  property on the current context item

``<designator>:<propname>``
  property on the indicated item (for editing related information)

``<classname>-<N>:<propname>``
  property on the Nth new item of classname (generally for creating new
  items to attach to the current item)

Once we have determined the "propname", we check to see if it is one of
the special form values:

``@required``
  The named property values must be supplied or a ValueError will be
  raised.

``@remove@<propname>=id(s)``
  The ids will be removed from the multilink property.

``:add:<propname>=id(s)``
  The ids will be added to the multilink property.

``:link:<propname>=<designator>``
  Used to add a link to new items created during edit. These are
  collected and returned in ``all_links``. This will result in an
  additional linking operation (either Link set or Multilink append)
  after the edit/create is done using ``all_props`` in ``_editnodes``.
  The <propname> on the current item will be set/appended the id of the
  newly created item of class <designator> (where <designator> must be
  <classname>-<N>).

Any of the form variables may be prefixed with a classname or
designator.

Two special form values are supported for backwards compatibility:

``:note``
  create a message (with content, author and date), linked to the
  context item. This is ALWAYS designated "msg-1".
``:file``
  create a file, attached to the current item and any message created by
  :note. This is ALWAYS designated "file-1".


Spool Section
~~~~~~~~~~~~~

The spool section lists related information like the messages and files
of an issue.

TODO


History Section
~~~~~~~~~~~~~~~

The final section displayed is the history of the item - its database
journal. This is generally generated with the template::

 <tal:block tal:replace="structure context/history" />

*To be done:*

*The actual history entries of the item may be accessed for manual
templating through the "journal" method of the item*::

 <tal:block tal:repeat="entry context/journal">
  a journal entry
 </tal:block>

*where each journal entry is an HTMLJournalEntry.*

Defining new web actions
------------------------

You may define new actions to be triggered by the ``@action`` form
variable. These are added to the tracker ``interfaces.py`` as methods on
the ``Client`` class. 

Adding action methods takes three steps; first you `define the new
action method`_, then you `register the action method`_ with the cgi
interface so it may be triggered by the ``@action`` form variable.
Finally you `use the new action`_ in your HTML form.

See "`setting up a "wizard" (or "druid") for controlled adding of
issues`_" for an example.


Define the new action method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The action methods have the following interface::

    def myActionMethod(self):
        ''' Perform some action. No return value is required.
        '''

The *self* argument is an instance of your tracker ``instance.Client``
class - thus it's mostly implemented by ``roundup.cgi.Client``. See the
docstring of that class for details of what it can do.

The method will typically check the ``self.form`` variable's contents.
It may then:

- add information to ``self.ok_message`` or ``self.error_message``
- change the ``self.template`` variable to alter what the user will see
  next
- raise Unauthorised, SendStaticFile, SendFile, NotFound or Redirect
  exceptions


Register the action method
~~~~~~~~~~~~~~~~~~~~~~~~~~

The method is now written, but isn't available to the user until you add
it to the `instance.Client`` class ``actions`` variable, like so::

    actions = client.Class.actions + (
        ('myaction', 'myActionMethod'),
    )

This maps the action name "myaction" to the action method we defined.


Use the new action
~~~~~~~~~~~~~~~~~~

In your HTML form, add a hidden form element like so::

  <input type="hidden" name="@action" value="myaction">

where "myaction" is the name you registered in the previous step.


Examples
========

.. contents::
   :local:
   :depth: 1


Adding a new field to the classic schema
----------------------------------------

This example shows how to add a new constrained property (i.e. a
selection of distinct values) to your tracker.


Introduction
~~~~~~~~~~~~

To make the classic schema of roundup useful as a TODO tracking system
for a group of systems administrators, it needed an extra data field per
issue: a category.

This would let sysadmins quickly list all TODOs in their particular area
of interest without having to do complex queries, and without relying on
the spelling capabilities of other sysadmins (a losing proposition at
best).


Adding a field to the database
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the easiest part of the change. The category would just be a
plain string, nothing fancy. To change what is in the database you need
to add some lines to the ``open()`` function in ``dbinit.py``. Under the
comment::

    # add any additional database schema configuration here

add::

    category = Class(db, "category", name=String())
    category.setkey("name")

Here we are setting up a chunk of the database which we are calling
"category". It contains a string, which we are refering to as "name" for
lack of a more imaginative title. (Since "name" is one of the properties
that Roundup looks for on items if you do not set a key for them, it's
probably a good idea to stick with it for new classes if at all
appropriate.) Then we are setting the key of this chunk of the database
to be that "name". This is equivalent to an index for database types.
This also means that there can only be one category with a given name.

Adding the above lines allows us to create categories, but they're not
tied to the issues that we are going to be creating. It's just a list of
categories off on its own, which isn't much use. We need to link it in
with the issues. To do that, find the lines in the ``open()`` function
in ``dbinit.py`` which set up the "issue" class, and then add a link to
the category::

    issue = IssueClass(db, "issue", ... ,
        category=Multilink("category"), ... )

The ``Multilink()`` means that each issue can have many categories. If
you were adding something with a one-to-one relationship to issues (such
as the "assignedto" property), use ``Link()`` instead.

That is all you need to do to change the schema. The rest of the effort
is fiddling around so you can actually use the new category.


Populating the new category class
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you haven't initialised the database with the roundup-admin
"initialise" command, then you can add the following to the tracker
``dbinit.py`` in the ``init()`` function under the comment::

    # add any additional database create steps here - but only if you
    # haven't initialised the database with the admin "initialise" command

Add::

     category = db.getclass('category')
     category.create(name="scipy", order="1")
     category.create(name="chaco", order="2")
     category.create(name="weave", order="3")

If the database has already been initalised, then you need to use the
``roundup-admin`` tool::

     % roundup-admin -i <tracker home>
     Roundup <version> ready for input.
     Type "help" for help.
     roundup> create category name=scipy order=1
     1
     roundup> create category name=chaco order=1
     2
     roundup> create category name=weave order=1
     3
     roundup> exit...
     There are unsaved changes. Commit them (y/N)? y

TODO: explain why order=1 in each case. Also, does key get set to "name"
automatically when added via roundup-admin?


Setting up security on the new objects
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

By default only the admin user can look at and change objects. This
doesn't suit us, as we want any user to be able to create new categories
as required, and obviously everyone needs to be able to view the
categories of issues for it to be useful.

We therefore need to change the security of the category objects. This
is also done in the ``open()`` function of ``dbinit.py``.

There are currently two loops which set up permissions and then assign
them to various roles. Simply add the new "category" to both lists::

    # new permissions for this schema
    for cl in 'issue', 'file', 'msg', 'user', 'category':
        db.security.addPermission(name="Edit", klass=cl,
            description="User is allowed to edit "+cl)
        db.security.addPermission(name="View", klass=cl,
            description="User is allowed to access "+cl)

    # Assign the access and edit permissions for issue, file and message
    # to regular users now
    for cl in 'issue', 'file', 'msg', 'category':
        p = db.security.getPermission('View', cl)
        db.security.addPermissionToRole('User', p)
        p = db.security.getPermission('Edit', cl)
        db.security.addPermissionToRole('User', p)

So you are in effect doing the following (with 'cl' substituted by its
value)::

    db.security.addPermission(name="Edit", klass='category',
        description="User is allowed to edit "+'category')
    db.security.addPermission(name="View", klass='category',
        description="User is allowed to access "+'category')

which is creating two permission types; that of editing and viewing
"category" objects respectively. Then the following lines assign those
new permissions to the "User" role, so that normal users can view and
edit "category" objects::

    p = db.security.getPermission('View', 'category')
    db.security.addPermissionToRole('User', p)

    p = db.security.getPermission('Edit', 'category')
    db.security.addPermissionToRole('User', p)

This is all the work that needs to be done for the database. It will
store categories, and let users view and edit them. Now on to the
interface stuff.


Changing the web left hand frame
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We need to give the users the ability to create new categories, and the
place to put the link to this functionality is in the left hand function
bar, under the "Issues" area. The file that defines how this area looks
is ``html/page``, which is what we are going to be editing next.

If you look at this file you can see that it contains a lot of
"classblock" sections which are chunks of HTML that will be included or
excluded in the output depending on whether the condition in the
classblock is met. Under the end of the classblock for issue is where we
are going to add the category code::

  <p class="classblock"
     tal:condition="python:request.user.hasPermission('View', 'category')">
   <b>Categories</b><br>
   <a tal:condition="python:request.user.hasPermission('Edit', 'category')"
      href="category?@template=item">New Category<br></a>
  </p>

The first two lines is the classblock definition, which sets up a
condition that only users who have "View" permission for the "category"
object will have this section included in their output. Next comes a
plain "Categories" header in bold. Everyone who can view categories will
get that.

Next comes the link to the editing area of categories. This link will
only appear if the condition - that the user has "Edit" permissions for
the "category" objects - is matched. If they do have permission then
they will get a link to another page which will let the user add new
categories.

Note that if you have permission to *view* but not to *edit* categories,
then all you will see is a "Categories" header with nothing underneath
it. This is obviously not very good interface design, but will do for
now. I just claim that it is so I can add more links in this section
later on. However to fix the problem you could change the condition in
the classblock statement, so that only users with "Edit" permission
would see the "Categories" stuff.


Setting up a page to edit categories
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We defined code in the previous section which let users with the
appropriate permissions see a link to a page which would let them edit
conditions. Now we have to write that page.

The link was for the *item* template of the *category* object. This
translates into Roundup looking for a file called ``category.item.html``
in the ``html`` tracker directory. This is the file that we are going to
write now.

First we add an info tag in a comment which doesn't affect the outcome
of the code at all, but is useful for debugging. If you load a page in a
browser and look at the page source, you can see which sections come
from which files by looking for these comments::

    <!-- category.item -->

Next we need to add in the METAL macro stuff so we get the normal page
trappings::

 <tal:block metal:use-macro="templates/page/macros/icing">
  <title metal:fill-slot="head_title">Category editing</title>
  <td class="page-header-top" metal:fill-slot="body_title">
   <h2>Category editing</h2>
  </td>
  <td class="content" metal:fill-slot="content">

Next we need to setup up a standard HTML form, which is the whole
purpose of this file. We link to some handy javascript which sends the
form through only once. This is to stop users hitting the send button
multiple times when they are impatient and thus having the form sent
multiple times::

    <form method="POST" onSubmit="return submit_once()"
          enctype="multipart/form-data">

Next we define some code which sets up the minimum list of fields that
we require the user to enter. There will be only one field - "name" - so
they better put something in it, otherwise the whole form is pointless::

    <input type="hidden" name="@required" value="name">

To get everything to line up properly we will put everything in a table,
and put a nice big header on it so the user has an idea what is
happening::

    <table class="form">
     <tr><th class="header" colspan="2">Category</th></tr>

Next, we need the field into which the user is going to enter the new
category. The "context.name.field(size=60)" bit tells Roundup to
generate a normal HTML field of size 60, and the contents of that field
will be the "name" variable of the current context (which is
"category"). The upshot of this is that when the user types something in
to the form, a new category will be created with that name::

    <tr>
     <th nowrap>Name</th>
     <td tal:content="structure python:context.name.field(size=60)">
     name</td>
    </tr>

Then a submit button so that the user can submit the new category::

    <tr>
     <td>&nbsp;</td>
     <td colspan="3" tal:content="structure context/submit">
      submit button will go here
     </td>
    </tr>

Finally we finish off the tags we used at the start to do the METAL
stuff::

  </td>
 </tal:block>

So putting it all together, and closing the table and form we get::

 <!-- category.item -->
 <tal:block metal:use-macro="templates/page/macros/icing">
  <title metal:fill-slot="head_title">Category editing</title>
  <td class="page-header-top" metal:fill-slot="body_title">
   <h2>Category editing</h2>
  </td>
  <td class="content" metal:fill-slot="content">
   <form method="POST" onSubmit="return submit_once()"
         enctype="multipart/form-data">

    <input type="hidden" name="@required" value="name">

    <table class="form">
     <tr><th class="header" colspan="2">Category</th></tr>

     <tr>
      <th nowrap>Name</th>
      <td tal:content="structure python:context.name.field(size=60)">
      name</td>
     </tr>

     <tr>
      <td>&nbsp;</td>
      <td colspan="3" tal:content="structure context/submit">
       submit button will go here
      </td>
     </tr>
    </table>
   </form>
  </td>
 </tal:block>

This is quite a lot to just ask the user one simple question, but there
is a lot of setup for basically one line (the form line) to do its work.
To add another field to "category" would involve one more line (well,
maybe a few extra to get the formatting correct).


Adding the category to the issue
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We now have the ability to create issues to our heart's content, but
that is pointless unless we can assign categories to issues.  Just like
the ``html/category.item.html`` file was used to define how to add a new
category, the ``html/issue.item.html`` is used to define how a new issue
is created.

Just like ``category.issue.html`` this file defines a form which has a
table to lay things out. It doesn't matter where in the table we add new
stuff, it is entirely up to your sense of aesthetics::

   <th nowrap>Category</th>
   <td><span tal:replace="structure context/category/field" />
       <span tal:replace="structure db/category/classhelp" />
   </td>

First, we define a nice header so that the user knows what the next
section is, then the middle line does what we are most interested in.
This ``context/category/field`` gets replaced by a field which contains
the category in the current context (the current context being the new
issue).

The classhelp lines generate a link (labelled "list") to a popup window
which contains the list of currently known categories.


Searching on categories
~~~~~~~~~~~~~~~~~~~~~~~

We can add categories, and create issues with categories. The next
obvious thing that we would like to be able to do, would be to search
for issues based on their category, so that, for example, anyone working
on the web server could look at all issues in the category "Web".

If you look for "Search Issues" in the 'html/page.html' file, you will
find that it looks something like 
``<a href="issue?@template=search">Search Issues</a>``. This shows us
that when you click on "Search Issues" it will be looking for a
``issue.search.html`` file to display. So that is the file that we will
change.

If you look at this file it should be starting to seem familiar, although it
does use some new macros. You can add the new category search code anywhere you
like within that form::

  <tr tal:define="name string:category;
                  db_klass string:category;
                  db_content string:name;">
    <th>Priority:</th>
    <td metal:use-macro="search_select"></td>
    <td metal:use-macro="column_input"></td>
    <td metal:use-macro="sort_input"></td>
    <td metal:use-macro="group_input"></td>
  </tr>

The definitions in the <tr> opening tag are used by the macros:

- search_select expands to a drop-down box with all categories using db_klass
  and db_content.
- column_input expands to a checkbox for selecting what columns should be
  displayed.
- sort_input expands to a radio button for selecting what property should be
  sorted on.
- group_input expands to a radio button for selecting what property should be
  group on.

The category search code above would expand to the following::

  <tr>
    <th>Category:</th>
    <td>
      <select name="category">
        <option value="">don't care</option>
        <option value="">------------</option>      
        <option value="1">scipy</option>
        <option value="2">chaco</option>
        <option value="3">weave</option>
      </select>
    </td>
    <td><input type="checkbox" name=":columns" value="category"></td>
    <td><input type="radio" name=":sort" value="category"></td>
    <td><input type="radio" name=":group" value="category"></td>
  </tr>

Adding category to the default view
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We can now add categories, add issues with categories, and search for
issues based on categories. This is everything that we need to do;
however, there is some more icing that we would like. I think the
category of an issue is important enough that it should be displayed by
default when listing all the issues.

Unfortunately, this is a bit less obvious than the previous steps. The
code defining how the issues look is in ``html/issue.index.html``. This
is a large table with a form down at the bottom for redisplaying and so
forth. 

Firstly we need to add an appropriate header to the start of the table::

    <th tal:condition="request/show/category">Category</th>

The *condition* part of this statement is to avoid displaying the
Category column if the user has selected not to see it.

The rest of the table is a loop which will go through every issue that
matches the display criteria. The loop variable is "i" - which means
that every issue gets assigned to "i" in turn.

The new part of code to display the category will look like this::

    <td tal:condition="request/show/category"
        tal:content="i/category"></td>

The condition is the same as above: only display the condition when the
user hasn't asked for it to be hidden. The next part is to set the
content of the cell to be the category part of "i" - the current issue.

Finally we have to edit ``html/page.html`` again. This time, we need to
tell it that when the user clicks on "Unasigned Issues" or "All Issues",
the category column should be included in the resulting list. If you
scroll down the page file, you can see the links with lots of options.
The option that we are interested in is the ``:columns=`` one which
tells roundup which fields of the issue to display. Simply add
"category" to that list and it all should work.


Adding in state transition control
----------------------------------

Sometimes tracker admins want to control the states that users may move
issues to. You can do this by following these steps:

1. make "status" a required variable. This is achieved by adding the
   following to the top of the form in the ``issue.item.html``
   template::

     <input type="hidden" name="@required" value="status">

   this will force users to select a status.

2. add a Multilink property to the status class::

     stat = Class(db, "status", ... , transitions=Multilink('status'),
                  ...)

   and then edit the statuses already created, either:

   a. through the web using the class list -> status class editor, or
   b. using the roundup-admin "set" command.

3. add an auditor module ``checktransition.py`` in your tracker's
   ``detectors`` directory, for example::

     def checktransition(db, cl, nodeid, newvalues):
         ''' Check that the desired transition is valid for the "status"
             property.
         '''
         if not newvalues.has_key('status'):
             return
         current = cl.get(nodeid, 'status')
         new = newvalues['status']
         if new == current:
             return
         ok = db.status.get(current, 'transitions')
         if new not in ok:
             raise ValueError, 'Status not allowed to move from "%s" to "%s"'%(
                 db.status.get(current, 'name'), db.status.get(new, 'name'))

     def init(db):
         db.issue.audit('set', checktransition)

4. in the ``issue.item.html`` template, change the status editing bit
   from::

    <th nowrap>Status</th>
    <td tal:content="structure context/status/menu">status</td>

   to::

    <th nowrap>Status</th>
    <td>
     <select tal:condition="context/id" name="status">
      <tal:block tal:define="ok context/status/transitions"
                 tal:repeat="state db/status/list">
       <option tal:condition="python:state.id in ok"
               tal:attributes="
                    value state/id;
                    selected python:state.id == context.status.id"
               tal:content="state/name"></option>
      </tal:block>
     </select>
     <tal:block tal:condition="not:context/id"
                tal:replace="structure context/status/menu" />
    </td>

   which displays only the allowed status to transition to.


Displaying only message summaries in the issue display
------------------------------------------------------

Alter the issue.item template section for messages to::

 <table class="messages" tal:condition="context/messages">
  <tr><th colspan="5" class="header">Messages</th></tr>
  <tr tal:repeat="msg context/messages">
   <td><a tal:attributes="href string:msg${msg/id}"
          tal:content="string:msg${msg/id}"></a></td>
   <td tal:content="msg/author">author</td>
   <td nowrap tal:content="msg/date/pretty">date</td>
   <td tal:content="msg/summary">summary</td>
   <td>
    <a tal:attributes="href string:?@remove@messages=${msg/id}&@action=edit">
    remove</a>
   </td>
  </tr>
 </table>

Restricting the list of users that are assignable to a task
-----------------------------------------------------------

1. In your tracker's "dbinit.py", create a new Role, say "Developer"::

     db.security.addRole(name='Developer', description='A developer')

2. Just after that, create a new Permission, say "Fixer", specific to
   "issue"::

     p = db.security.addPermission(name='Fixer', klass='issue',
         description='User is allowed to be assigned to fix issues')

3. Then assign the new Permission to your "Developer" Role::

     db.security.addPermissionToRole('Developer', p)

4. In the issue item edit page ("html/issue.item.html" in your tracker
   directory), use the new Permission in restricting the "assignedto"
   list::

    <select name="assignedto">
     <option value="-1">- no selection -</option>
     <tal:block tal:repeat="user db/user/list">
     <option tal:condition="python:user.hasPermission(
                                'Fixer', context._classname)"
             tal:attributes="
                value user/id;
                selected python:user.id == context.assignedto"
             tal:content="user/realname"></option>
     </tal:block>
    </select>

For extra security, you may wish to setup an auditor to enforce the
Permission requirement (install this as "assignedtoFixer.py" in your
tracker "detectors" directory)::

  def assignedtoMustBeFixer(db, cl, nodeid, newvalues):
      ''' Ensure the assignedto value in newvalues is a used with the
          Fixer Permission
      '''
      if not newvalues.has_key('assignedto'):
          # don't care
          return
  
      # get the userid
      userid = newvalues['assignedto']
      if not db.security.hasPermission('Fixer', userid, cl.classname):
          raise ValueError, 'You do not have permission to edit %s'%cl.classname

  def init(db):
      db.issue.audit('set', assignedtoMustBeFixer)
      db.issue.audit('create', assignedtoMustBeFixer)

So now, if an edit action attempts to set "assignedto" to a user that
doesn't have the "Fixer" Permission, the error will be raised.


Setting up a "wizard" (or "druid") for controlled adding of issues
------------------------------------------------------------------

1. Set up the page templates you wish to use for data input. My wizard
   is going to be a two-step process: first figuring out what category
   of issue the user is submitting, and then getting details specific to
   that category. The first page includes a table of help, explaining
   what the category names mean, and then the core of the form::

    <form method="POST" onSubmit="return submit_once()"
          enctype="multipart/form-data">
      <input type="hidden" name="@template" value="add_page1">
      <input type="hidden" name="@action" value="page1submit">

      <strong>Category:</strong>
      <tal:block tal:replace="structure context/category/menu" />
      <input type="submit" value="Continue">
    </form>

   The next page has the usual issue entry information, with the
   addition of the following form fragments::

    <form method="POST" onSubmit="return submit_once()"
          enctype="multipart/form-data"
          tal:condition="context/is_edit_ok"
          tal:define="cat request/form/category/value">

      <input type="hidden" name="@template" value="add_page2">
      <input type="hidden" name="@required" value="title">
      <input type="hidden" name="category" tal:attributes="value cat">
       .
       .
       .
    </form>

   Note that later in the form, I test the value of "cat" include form
   elements that are appropriate. For example::

    <tal:block tal:condition="python:cat in '6 10 13 14 15 16 17'.split()">
     <tr>
      <th nowrap>Operating System</th>
      <td tal:content="structure context/os/field"></td>
     </tr>
     <tr>
      <th nowrap>Web Browser</th>
      <td tal:content="structure context/browser/field"></td>
     </tr>
    </tal:block>

   ... the above section will only be displayed if the category is one
   of 6, 10, 13, 14, 15, 16 or 17.

3. Determine what actions need to be taken between the pages - these are
   usually to validate user choices and determine what page is next. Now
   encode those actions in methods on the ``interfaces.Client`` class
   and insert hooks to those actions in the "actions" attribute on that
   class, like so::

    actions = client.Client.actions + (
        ('page1_submit', 'page1SubmitAction'),
    )

    def page1SubmitAction(self):
        ''' Verify that the user has selected a category, and then move
            on to page 2.
        '''
        category = self.form['category'].value
        if category == '-1':
            self.error_message.append('You must select a category of report')
            return
        # everything's ok, move on to the next page
        self.template = 'add_page2'

4. Use the usual "new" action as the ``@action`` on the final page, and
   you're done (the standard context/submit method can do this for you).


Using an external password validation source
--------------------------------------------

We have a centrally-managed password changing system for our users. This
results in a UN*X passwd-style file that we use for verification of
users. Entries in the file consist of ``name:password`` where the
password is encrypted using the standard UN*X ``crypt()`` function (see
the ``crypt`` module in your Python distribution). An example entry
would be::

    admin:aamrgyQfDFSHw

Each user of Roundup must still have their information stored in the
Roundup database - we just use the passwd file to check their password.
To do this, we add the following code to our ``Client`` class in the
tracker home ``interfaces.py`` module::

    def verifyPassword(self, userid, password):
        # get the user's username
        username = self.db.user.get(userid, 'username')

        # the passwords are stored in the "passwd.txt" file in the
        # tracker home
        file = os.path.join(self.db.config.TRACKER_HOME, 'passwd.txt')

        # see if we can find a match
        for ent in [line.strip().split(':') for line in
                                            open(file).readlines()]:
            if ent[0] == username:
                return crypt.crypt(password, ent[1][:2]) == ent[1]

        # user doesn't exist in the file
        return 0

What this does is look through the file, line by line, looking for a
name that matches.

We also remove the redundant password fields from the ``user.item``
template.


Adding a "vacation" flag to users for stopping nosy messages
------------------------------------------------------------

When users go on vacation and set up vacation email bouncing, you'll
start to see a lot of messages come back through Roundup "Fred is on
vacation". Not very useful, and relatively easy to stop.

1. add a "vacation" flag to your users::

         user = Class(db, "user",
                    username=String(),   password=Password(),
                    address=String(),    realname=String(),
                    phone=String(),      organisation=String(),
                    alternate_addresses=String(),
                    roles=String(), queries=Multilink("query"),
                    vacation=Boolean())

2. So that users may edit the vacation flags, add something like the
   following to your ``user.item`` template::

     <tr>
      <th>On Vacation</th> 
      <td tal:content="structure context/vacation/field">vacation</td> 
     </tr> 

3. edit your detector ``nosyreactor.py`` so that the ``nosyreaction()``
   consists of::

    def nosyreaction(db, cl, nodeid, oldvalues):
        # send a copy of all new messages to the nosy list
        for msgid in determineNewMessages(cl, nodeid, oldvalues):
            try:
                users = db.user
                messages = db.msg

                # figure the recipient ids
                sendto = []
                r = {}
                recipients = messages.get(msgid, 'recipients')
                for recipid in messages.get(msgid, 'recipients'):
                    r[recipid] = 1

                # figure the author's id, and indicate they've received
                # the message
                authid = messages.get(msgid, 'author')

                # possibly send the message to the author, as long as
                # they aren't anonymous
                if (db.config.MESSAGES_TO_AUTHOR == 'yes' and
                        users.get(authid, 'username') != 'anonymous'):
                    sendto.append(authid)
                r[authid] = 1

                # now figure the nosy people who weren't recipients
                nosy = cl.get(nodeid, 'nosy')
                for nosyid in nosy:
                    # Don't send nosy mail to the anonymous user (that
                    # user shouldn't appear in the nosy list, but just
                    # in case they do...)
                    if users.get(nosyid, 'username') == 'anonymous':
                        continue
                    # make sure they haven't seen the message already
                    if not r.has_key(nosyid):
                        # send it to them
                        sendto.append(nosyid)
                        recipients.append(nosyid)

                # generate a change note
                if oldvalues:
                    note = cl.generateChangeNote(nodeid, oldvalues)
                else:
                    note = cl.generateCreateNote(nodeid)

                # we have new recipients
                if sendto:
                    # filter out the people on vacation
                    sendto = [i for i in sendto 
                              if not users.get(i, 'vacation', 0)]

                    # map userids to addresses
                    sendto = [users.get(i, 'address') for i in sendto]

                    # update the message's recipients list
                    messages.set(msgid, recipients=recipients)

                    # send the message
                    cl.send_message(nodeid, msgid, note, sendto)
            except roundupdb.MessageSendError, message:
                raise roundupdb.DetectorError, message

   Note that this is the standard nosy reaction code, with the small
   addition of::

    # filter out the people on vacation
    sendto = [i for i in sendto if not users.get(i, 'vacation', 0)]

   which filters out the users that have the vacation flag set to true.


Adding a time log to your issues
--------------------------------

We want to log the dates and amount of time spent working on issues, and
be able to give a summary of the total time spent on a particular issue.

1. Add a new class to your tracker ``dbinit.py``::

    # storage for time logging
    timelog = Class(db, "timelog", period=Interval())

   Note that we automatically get the date of the time log entry
   creation through the standard property "creation".

2. Link to the new class from your issue class (again, in
   ``dbinit.py``)::

    issue = IssueClass(db, "issue", 
                    assignedto=Link("user"), topic=Multilink("keyword"),
                    priority=Link("priority"), status=Link("status"),
                    times=Multilink("timelog"))

   the "times" property is the new link to the "timelog" class.

3. We'll need to let people add in times to the issue, so in the web
   interface we'll have a new entry field. This is a special field
   because unlike the other fields in the issue.item template, it
   affects a different item (a timelog item) and not the template's
   item, an issue. We have a special syntax for form fields that affect
   items other than the template default item (see the cgi 
   documentation on `special form variables`_). In particular, we add a
   field to capture a new timelog item's perdiod::

    <tr> 
     <th nowrap>Time Log</th> 
     <td colspan=3><input type="text" name="timelog-1@period" /> 
      <br />(enter as '3y 1m 4d 2:40:02' or parts thereof) 
     </td> 
    </tr> 
         
   and another hidden field that links that new timelog item (new
   because it's marked as having id "-1") to the issue item. It looks
   like this::

     <input type="hidden" name="@link@times" value="timelog-1" />

   On submission, the "-1" timelog item will be created and assigned a
   real item id. The "times" property of the issue will have the new id
   added to it.

4. We want to display a total of the time log times that have been
   accumulated for an issue. To do this, we'll need to actually write
   some Python code, since it's beyond the scope of PageTemplates to
   perform such calculations. We do this by adding a method to the
   TemplatingUtils class in our tracker ``interfaces.py`` module::

    class TemplatingUtils:
        ''' Methods implemented on this class will be available to HTML
            templates through the 'utils' variable.
        '''
        def totalTimeSpent(self, times):
            ''' Call me with a list of timelog items (which have an
                Interval "period" property)
            '''
            total = Interval('')
            for time in times:
                total += time.period._value
            return total

   Replace the ``pass`` line as we did in step 4 above with the Client
   class. As indicated in the docstrings, we will be able to access the
   ``totalTimeSpent`` method via the ``utils`` variable in our
   templates.

5. Display the time log for an issue::

     <table class="otherinfo" tal:condition="context/times">
      <tr><th colspan="3" class="header">Time Log
       <tal:block
            tal:replace="python:utils.totalTimeSpent(context.times)" />
      </th></tr>
      <tr><th>Date</th><th>Period</th><th>Logged By</th></tr>
      <tr tal:repeat="time context/times">
       <td tal:content="time/creation"></td>
       <td tal:content="time/period"></td>
       <td tal:content="time/creator"></td>
      </tr>
     </table>

   I put this just above the Messages log in my issue display. Note our
   use of the ``totalTimeSpent`` method which will total up the times
   for the issue and return a new Interval. That will be automatically
   displayed in the template as text like "+ 1y 2:40" (1 year, 2 hours
   and 40 minutes).

8. If you're using a persistent web server - roundup-server or
   mod_python for example - then you'll need to restart that to pick up
   the code changes. When that's done, you'll be able to use the new
   time logging interface.

Using a UN*X passwd file as the user database
---------------------------------------------

On some systems the primary store of users is the UN*X passwd file. It
holds information on users such as their username, real name, password
and primary user group.

Roundup can use this store as its primary source of user information,
but it needs additional information too - email address(es), roundup
Roles, vacation flags, roundup hyperdb item ids, etc. Also, "retired"
users must still exist in the user database, unlike some passwd files in
which the users are removed when they no longer have access to a system.

To make use of the passwd file, we therefore synchronise between the two
user stores. We also use the passwd file to validate the user logins, as
described in the previous example, `using an external password
validation source`_. We keep the users lists in sync using a fairly
simple script that runs once a day, or several times an hour if more
immediate access is needed. In short, it:

1. parses the passwd file, finding usernames, passwords and real names,
2. compares that list to the current roundup user list:

   a. entries no longer in the passwd file are *retired*
   b. entries with mismatching real names are *updated*
   c. entries only exist in the passwd file are *created*

3. send an email to administrators to let them know what's been done.

The retiring and updating are simple operations, requiring only a call
to ``retire()`` or ``set()``. The creation operation requires more
information though - the user's email address and their roundup Roles.
We're going to assume that the user's email address is the same as their
login name, so we just append the domain name to that. The Roles are
determined using the passwd group identifier - mapping their UN*X group
to an appropriate set of Roles.

The script to perform all this, broken up into its main components, is
as follows. Firstly, we import the necessary modules and open the
tracker we're to work on::

    import sys, os, smtplib
    from roundup import instance, date

    # open the tracker
    tracker_home = sys.argv[1]
    tracker = instance.open(tracker_home)

Next we read in the *passwd* file from the tracker home::

    # read in the users
    file = os.path.join(tracker_home, 'users.passwd')
    users = [x.strip().split(':') for x in open(file).readlines()]

Handle special users (those to ignore in the file, and those who don't
appear in the file)::

    # users to not keep ever, pre-load with the users I know aren't
    # "real" users
    ignore = ['ekmmon', 'bfast', 'csrmail']

    # users to keep - pre-load with the roundup-specific users
    keep = ['comment_pool', 'network_pool', 'admin', 'dev-team',
            'cs_pool', 'anonymous', 'system_pool', 'automated']

Now we map the UN*X group numbers to the Roles that users should have::

    roles = {
     '501': 'User,Tech',  # tech
     '502': 'User',       # finance
     '503': 'User,CSR',   # customer service reps
     '504': 'User',       # sales
     '505': 'User',       # marketing
    }

Now we do all the work. Note that the body of the script (where we have
the tracker database open) is wrapped in a ``try`` / ``finally`` clause,
so that we always close the database cleanly when we're finished. So, we
now do all the work::

    # open the database
    db = tracker.open('admin')
    try:
        # store away messages to send to the tracker admins
        msg = []

        # loop over the users list read in from the passwd file
        for user,passw,uid,gid,real,home,shell in users:
            if user in ignore:
                # this user shouldn't appear in our tracker
                continue
            keep.append(user)
            try:
                # see if the user exists in the tracker
                uid = db.user.lookup(user)

                # yes, they do - now check the real name for correctness
                if real != db.user.get(uid, 'realname'):
                    db.user.set(uid, realname=real)
                    msg.append('FIX %s - %s'%(user, real))
            except KeyError:
                # nope, the user doesn't exist
                db.user.create(username=user, realname=real,
                    address='%s@ekit-inc.com'%user, roles=roles[gid])
                msg.append('ADD %s - %s (%s)'%(user, real, roles[gid]))

        # now check that all the users in the tracker are also in our
        # "keep" list - retire those who aren't
        for uid in db.user.list():
            user = db.user.get(uid, 'username')
            if user not in keep:
                db.user.retire(uid)
                msg.append('RET %s'%user)

        # if we did work, then send email to the tracker admins
        if msg:
            # create the email
            msg = '''Subject: %s user database maintenance

            %s
            '''%(db.config.TRACKER_NAME, '\n'.join(msg))

            # send the email
            smtp = smtplib.SMTP(db.config.MAILHOST)
            addr = db.config.ADMIN_EMAIL
            smtp.sendmail(addr, addr, msg)

        # now we're done - commit the changes
        db.commit()
    finally:
        # always close the database cleanly
        db.close()

And that's it!


Using an LDAP database for user information
-------------------------------------------

A script that reads users from an LDAP store using
http://python-ldap.sf.net/ and then compares the list to the users in the
roundup user database would be pretty easy to write. You'd then have it run
once an hour / day (or on demand if you can work that into your LDAP store
workflow). See the example `Using a UN*X passwd file as the user database`_
for more information about doing this.

To authenticate off the LDAP store (rather than using the passwords in the
roundup user database) you'd use the same python-ldap module inside an
extension to the cgi interface. You'd do this by adding a method called
"verifyPassword" to the Client class in your tracker's interfaces.py
module. The method is implemented by default as::

    def verifyPassword(self, userid, password):
        ''' Verify the password that the user has supplied
        '''
        stored = self.db.user.get(self.userid, 'password')
        if password == stored:
            return 1
        if not password and not stored:
            return 1
        return 0

So you could reimplement this as something like::

    def verifyPassword(self, userid, password):
        ''' Verify the password that the user has supplied
        '''
        # look up some unique LDAP information about the user
        username = self.db.user.get(self.userid, 'username')
        # now verify the password supplied against the LDAP store


Enabling display of either message summaries or the entire messages
-------------------------------------------------------------------

This is pretty simple - all we need to do is copy the code from the
example `displaying only message summaries in the issue display`_ into
our template alongside the summary display, and then introduce a switch
that shows either one or the other. We'll use a new form variable,
``@whole_messages`` to achieve this::

 <table class="messages" tal:condition="context/messages">
  <tal:block tal:condition="not:request/form/@whole_messages/value | python:0">
   <tr><th colspan="3" class="header">Messages</th>
       <th colspan="2" class="header">
         <a href="?@whole_messages=yes">show entire messages</a>
       </th>
   </tr>
   <tr tal:repeat="msg context/messages">
    <td><a tal:attributes="href string:msg${msg/id}"
           tal:content="string:msg${msg/id}"></a></td>
    <td tal:content="msg/author">author</td>
    <td nowrap tal:content="msg/date/pretty">date</td>
    <td tal:content="msg/summary">summary</td>
    <td>
     <a tal:attributes="href string:?@remove@messages=${msg/id}&@action=edit">remove</a>
    </td>
   </tr>
  </tal:block>

  <tal:block tal:condition="request/form/@whole_messages/value | python:0">
   <tr><th colspan="2" class="header">Messages</th>
       <th class="header">
         <a href="?@whole_messages=">show only summaries</a>
       </th>
   </tr>
   <tal:block tal:repeat="msg context/messages">
    <tr>
     <th tal:content="msg/author">author</th>
     <th nowrap tal:content="msg/date/pretty">date</th>
     <th style="text-align: right">
      (<a tal:attributes="href string:?@remove@messages=${msg/id}&@action=edit">remove</a>)
     </th>
    </tr>
    <tr><td colspan="3" tal:content="msg/content"></td></tr>
   </tal:block>
  </tal:block>
 </table>


Blocking issues that depend on other issues
-------------------------------------------

We needed the ability to mark certain issues as "blockers" - that is,
they can't be resolved until another issue (the blocker) they rely on is
resolved. To achieve this:

1. Create a new property on the issue Class,
   ``blockers=Multilink("issue")``. Edit your tracker's dbinit.py file.
   Where the "issue" class is defined, something like::

    issue = IssueClass(db, "issue", 
                    assignedto=Link("user"), topic=Multilink("keyword"),
                    priority=Link("priority"), status=Link("status"))

   add the blockers entry like so::

    issue = IssueClass(db, "issue", 
                    blockers=Multilink("issue"),
                    assignedto=Link("user"), topic=Multilink("keyword"),
                    priority=Link("priority"), status=Link("status"))

2. Add the new "blockers" property to the issue.item edit page, using
   something like::

    <th nowrap>Waiting On</th>
    <td>
     <span tal:replace="structure python:context.blockers.field(showid=1,
                                  size=20)" />
     <span tal:replace="structure python:db.issue.classhelp('id,title')" />
     <span tal:condition="context/blockers"
           tal:repeat="blk context/blockers">
      <br>View: <a tal:attributes="href string:issue${blk/id}"
                   tal:content="blk/id"></a>
     </span>

   You'll need to fiddle with your item page layout to find an
   appropriate place to put it - I'll leave that fun part up to you.
   Just make sure it appears in the first table, possibly somewhere near
   the "superseders" field.

3. Create a new detector module (attached) which enforces the rules:

   - issues may not be resolved if they have blockers
   - when a blocker is resolved, it's removed from issues it blocks

   The contents of the detector should be something like this::

    def blockresolution(db, cl, nodeid, newvalues):
        ''' If the issue has blockers, don't allow it to be resolved.
        '''
        if nodeid is None:
            blockers = []
        else:
            blockers = cl.get(nodeid, 'blockers')
        blockers = newvalues.get('blockers', blockers)

        # don't do anything if there's no blockers or the status hasn't
        # changed
        if not blockers or not newvalues.has_key('status'):
            return

        # get the resolved state ID
        resolved_id = db.status.lookup('resolved')

        # format the info
        u = db.config.TRACKER_WEB
        s = ', '.join(['<a href="%sissue%s">%s</a>'%(
                        u,id,id) for id in blockers])
        if len(blockers) == 1:
            s = 'issue %s is'%s
        else:
            s = 'issues %s are'%s

        # ok, see if we're trying to resolve
        if newvalues['status'] == resolved_id:
            raise ValueError, "This issue can't be resolved until %s resolved."%s

    def resolveblockers(db, cl, nodeid, newvalues):
        ''' When we resolve an issue that's a blocker, remove it from the
            blockers list of the issue(s) it blocks.
        '''
        if not newvalues.has_key('status'):
            return

        # get the resolved state ID
        resolved_id = db.status.lookup('resolved')

        # interesting?
        if newvalues['status'] != resolved_id:
            return

        # yes - find all the blocked issues, if any, and remove me from
        # their blockers list
        issues = cl.find(blockers=nodeid)
        for issueid in issues:
            blockers = cl.get(issueid, 'blockers')
            if nodeid in blockers:
                blockers.remove(nodeid)
                cl.set(issueid, blockers=blockers)


    def init(db):
        # might, in an obscure situation, happen in a create
        db.issue.audit('create', blockresolution)
        db.issue.audit('set', blockresolution)

        # can only happen on a set
        db.issue.react('set', resolveblockers)

   Put the above code in a file called "blockers.py" in your tracker's
   "detectors" directory.

4. Finally, and this is an optional step, modify the tracker web page
   URLs so they filter out issues with any blockers. You do this by
   adding an additional filter on "blockers" for the value "-1". For
   example, the existing "Show All" link in the "page" template (in the
   tracker's "html" directory) looks like this::

     <a href="issue?:sort=-activity&:group=priority&:filter=status&:columns=id,activity,title,creator,assignedto,status&status=-1,1,2,3,4,5,6,7">Show All</a><br>

   modify it to add the "blockers" info to the URL (note, both the
   ":filter" *and* "blockers" values must be specified)::

     <a href="issue?:sort=-activity&:group=priority&:filter=status,blockers&blockers=-1&:columns=id,activity,title,creator,assignedto,status&status=-1,1,2,3,4,5,6,7">Show All</a><br>

That's it. You should now be able to set blockers on your issues. Note
that if you want to know whether an issue has any other issues dependent
on it (i.e. it's in their blockers list) you can look at the journal
history at the bottom of the issue page - look for a "link" event to
another issue's "blockers" property.


-------------------

Back to `Table of Contents`_

.. _`Table of Contents`: index.html
.. _`design documentation`: design.html