Epydoc Fields
=============

.. $Id: manual-fields.txt 1554 2007-02-27 03:31:56Z edloper $

Fields are used to describe specific properties of a documented object. For
example, fields can be used to define the parameters and return value of a
function; the instance variables of a class; and the author of a module. Each
field consists of a *tag*, an optional *argument*, and a *body*.

* The *tag* is a case-insensitive word that indicates what kind of
  documentation is given by the field.
* The optional *argument* specifies what object, parameter, or group is
  documented by the field.
* The *body* contains the main contents of the field.


Field Markup
------------

Each docstring markup langauge marks fields differently. The following table
shows the basic fields syntax for each markup language. For more information,
see the definition of field syntax for each markup language.


.. list-table::
   :header-rows: 1

   *  - Epytext
      - reStructuredText
      - Javadoc

   *  - .. parsed-literal::

            @\ *tag*: *body*...
            @\ *tag* *arg*: *body*...

      - .. parsed-literal::

            :\ *tag*: *body*...
            :\ *tag* *arg*: *body*...

      - .. parsed-literal::

            @\ *tag* *body*...
            @\ *tag* *arg* *body*...

   *  - `Definition of epytext fields`__
      - `Definition of ReStructuredText fields`__
      - `Definition of Javadoc fields`__

.. __: Fields_
.. __: http://docutils.sourceforge.net/spec/rst/reStructuredText.html
        #field-lists
.. __: http://java.sun.com/j2se/1.4.2/docs/tooldocs/solaris/javadoc.html
        #javadoctags


Supported Fields
----------------

The following table lists the fields that epydoc currently recognizes. Field
tags are written using epytext markup; if you are using a different markup
language, then you should adjust the markup accordingly.


Functions and Methods parameters
''''''''''''''''''''''''''''''''

``@param`` *p*: ...
    A description of the parameter *p* for a function or method.

``@type`` *p*: ...
    The expected type for the parameter *p*.

``@return``: ...
    The return value for a function or method.

``@rtype``: ...
    The type of the return value for a function or method.

``@keyword`` *p*: ...
    A description of the keyword parameter *p*.

``@raise`` *e*: ...
    A description of the circumstances under which a function or method
    raises exception *e*.

These tags can be used to specify attributes of parameters and return value
of function and methods. These tags are usually put in the the docstring of the
function to be documented.

.. note:: **constructor parameters**

    In C extension modules, extension classes cannot have a docstring attached
    to the ``__init__`` function; consequently it is not possible to document
    parameters and exceptions raised by the class constructor. To overcome this
    shortcoming, the tags ``@param``, ``@keyword``, ``@type``, ``@exception``
    are also allowed to appear in the class docstring. In this case they refer
    to constructor parameters.

``@param`` fields should be used to document any explicit parameter
(including the keyword parameter). ``@keyword`` fields should only be used
for non-explicit keyword parameters:

.. python::

    def plant(seed, *tools, **options):
        """
        @param seed: The seed that should be planted.
        @param tools: Tools that should be used to plant the seed.
        @param options: Any extra options for the planting.

        @keyword dig_deep: Plant the seed deep under ground.
        @keyword soak: Soak the seed before planting it.
        """
        #[...]

Since the ``@type`` field allows for arbitrary text, it does not
automatically create a crossreference link to the specified type, and is
not written in fixed-width font by default. If you want to create a
crossreference link to the type, or to write the type in a fixed-width
font, then you must use inline markup:

.. python::

    def ponder(person, time):
        """
        @param person: Who should think.
        @type person: L{Person} or L{Animal}
        @param time: How long they should think.
        @type time: C{int} or C{float}
        """
        #[...]


Variables parameters
''''''''''''''''''''

``@ivar`` *v*: ...
    A description of the class instance variable *v*.

``@cvar`` *v*: ...
    A description of the static class variable *v*.

``@var`` *v*: ...
    A description of the module variable *v*.

``@type`` *v*: ...
    The type of the variable *v*.

These tags are usually put in a module or class docstring. If the sources can
be parsed by Epydoc it is also possible to document the variable in their own
docstrings: see `variable docstrings`_

Epydoc considers class variables the ones defined directly defined in the
class body. A common Python idiom is to create instance variables settings
their default value in the class instead of the constructor (hopefully if the
default is immutable...).

If you want to force Epydoc to classify as instance variable one whose default
value is set at class level, you can describe it using the tag ``@ivar`` in the
context of a variable docstring:

.. python::

    class B:
        y = 42
        """@ivar: This is an instance variable."""


Properties parameters
'''''''''''''''''''''

``@type``: ...
    The type of the property.

The ``@type`` tag can be attached toa property docstring to specify its type.


Grouping and Sorting
'''''''''''''''''''''

``@group`` *g*: *c1,...,cn*
    Organizes a set of related children of a module or class into a group.
    *g* is the name of the group; and *c1,...,cn* are the names of the
    children in the group. To define multiple groups, use multiple group
    fields.

``@sort``: *c1,...,cn*
    Specifies the sort order for the children of a module or class.
    *c1,...,cn* are the names of the children, in the order in which they
    should appear. Any children that are not included in this list will
    appear after the children from this list, in alphabetical order.

These tags can be used to present groups of related items in a logical way.
They apply to modules and classes docstrings.

For the ``@group`` and ``@sort`` tags, asterisks (``*``) can be used to
specify multiple children at once. An asterisk in a child name will match
any substring:

.. python::

    class widget(size, weight, age):
        """
        @group Tools: zip, zap, *_tool
        @group Accessors: get_*
        @sort: get_*, set_*, unpack_*, cut
        """
        #[...]

.. note:: **group markers**

    It is also possible to group set of related items enclosing them
    into special comment starting with the *group markers* '``#{``' and '``#}``'
    The group title can be specified after the opening group marker. Example:

    .. python::

        #{ Database access functions

        def read(id):
            #[...]

        def store(item):
            #[...]

        def delete(id):
            #[...]

        # groups can't be nested, so a closing marker is not required here.

        #{ Web publish functions

        def get(request):
            #[...]

        def post(request):
            #[...]

        #}


Notes and Warnings
''''''''''''''''''

``@note``: ...
    A note about an object. Multiple note fields may be used to list
    separate notes.

``@attention``: ...
    An important note about an object. Multiple attention fields may be
    used to list separate notes.

``@bug``: ...
    A description of a bug in an object. Multiple bug fields may be used to
    report separate bugs.

    .. note::

        If any ``@bug`` field is used, the HTML writer will generate a the page
        ``bug-index.html``, containing links to all the items tagged with
        the field.

``@warning``: ...
    A warning about an object. Multiple warning fields may be used to
    report separate warnings.


Status
''''''

``@version``: ...
    The current version of an object.

``@todo`` [*ver*]: ...
    A planned change to an object. If the optional argument ver is given,
    then it specifies the version for which the change will be made.
    Multiple todo fields may be used if multiple changes are planned.

    .. note::

        If any ``@todo`` field is used, the HTML writer will generate a the
        page ``todo-index.html``, containing links to all the items tagged
        with the field.


``@deprecated``: ...
    Indicates that an object is deprecated. The body of the field describe
    the reason why the object is deprecated.

``@since``: ...
    The date or version when an object was first introduced.

``@status``: ...
    The current status of an object.

``@change``: ...
    A change log entry for this object.

``@permission``: ...
    The object access permission, for systems such Zope/Plone supporting
    this concept. It may be used more than once to specify multiple
    permissions.


Formal Conditions
'''''''''''''''''

``@requires``: ...
    A requirement for using an object. Multiple requires fields may be
    used if an object has multiple requirements.

``@precondition``: ...
    A condition that must be true before an object is used. Multiple
    precondition fields may be used if an object has multiple preconditions.

``@postcondition``: ...
    A condition that is guaranteed to be true after an object is used.
    Multiple postcondition fields may be used if an object has multiple
    postconditions.

``@invariant``: ...
    A condition which should always be true for an object. Multiple
    invariant fields may be used if an object has multiple invariants.


Bibliographic Information
'''''''''''''''''''''''''

``@author``: ...
    The author(s) of an object. Multiple author fields may be used if an
    object has multiple authors.

``@organization``: ...
    The organization that created or maintains an object.

``@copyright``: ...
    The copyright information for an object.

``@license``: ...
    The licensing information for an object.

``@contact``: ...
    Contact information for the author or maintainer of a module, class,
    function, or method. Multiple contact fields may be used if an object
    has multiple contacts.


Other fields
''''''''''''

``@summary``: ...
    A summary description for an object. This description overrides the
    default summary (which is constructed from the first sentence of the
    object's description).

``@see``: ...
    A description of a related topic. see fields typically use
    documentation crossreference links or external hyperlinks that link to
    the related topic.


Fields synonyms
---------------

Several fields have *synonyms*, or alternate tags. The following table lists
all field synonyms. Field tags are written using epytext markup; if you are
using a different markup language, then you should adjust the markup
accordingly.


.. list-table::
   :header-rows: 1

   * - Name
     - Synonims

   * - ``@param`` *p*: ...
     - | ``@parameter`` *p*: ...
       | ``@arg`` *p*: ...
       | ``@argument`` *p*: ...

   * - ``@return``: ...
     - ``@returns``: ...

   * - ``@rtype``: ...
     - ``@returntype``: ...

   * - ``@raise`` *e*: ...
     - | ``@raises`` *e*: ...
       | ``@except`` *e*: ...
       | ``@exception`` *e*: ...

   * - ``@keyword`` *p*: ...
     - | ``@kwarg`` *p*: ...
       | ``@kwparam`` *p*: ...

   * - ``@ivar`` *v*: ...
     - ``@ivariable`` *v*: ...

   * - ``@cvar`` *v*: ...
     - ``@cvariable`` *v*: ...

   * - ``@var`` *v*: ...
     - ``@variable`` *v*: ...

   * - ``@see``: ...
     - ``@seealso``: ...

   * - ``@warning``: ...
     - ``@warn``: ...

   * - ``@requires``: ...
     - | ``@require``: ...
       | ``@requirement``: ...

   * - ``@precondition``: ...
     - ``@precond``: ...

   * - ``@postcondition``: ...
     - ``@postcond``: ...

   * - ``@organization``: ...
     - ``@org``: ...

   * - ``@copyright``: ...
     - ``@(c)``: ...

   * - ``@change``: ...
     - ``@changed``: ...


Module metadata variables
-------------------------

Some module variables are commonly used as module metadata. Epydoc can use the
value provided by these variables as alternate form for tags. The following
table lists the recognized variables and the tag they replace. Customized
metadata variables can be added using the method described in `Adding New
Fields`_.

.. list-table::
   :header-rows: 1

   * - Tag
     - Variable

   * - ``@author``
     - ``__author__``

   * - ``@authors``
     - ``__authors__``

   * - ``@contact``
     - ``__contact__``

   * - ``@copyright``
     - ``__copyright__``

   * - ``@license``
     - ``__license__``

   * - ``@deprecated``
     - ``__deprecated__``

   * - ``@date``
     - ``__date__``

   * - ``@version``
     - ``__version__``


Adding New Fields
-----------------

New fields can be defined for the docstrings in a module using the special
``@newfield`` tag (or its synonym, ``@deffield``). This tag has the following
syntax:

 .. parsed-literal::

    @newfield *tag*: *label* [, *plural* ]

Where *tag* is the new tag that's being defined; *label* is a string that will
be used to mark this field in the generated output; and plural is the plural form
of label, if different.

New fields can be defined in any Python module. If they are defined in a
package, it will be possible to use the newly defined tag from every package
submodule.

Each new field will also define a `metadata variable`_ which can be used
to set the field value instead of the tag. For example, if a *revision*
tag has been defined with::

    @newfield revision: Revision

then it will be possible to set a value for the field using a module variable:

.. python::

    __revision__ = "1234"

.. _metadata variable: `Module metadata variables`_

The following example illustrates how the @newfield can be used:
Docstring Input	Rendered Output


.. list-table::
   :header-rows: 1

   * - Docstring Input
     - Rendered Output

   * - .. python::

        """
        @newfield corpus: Corpus, Corpora
        """

        def example():
            """
            @corpus: Bob's wordlist.
            @corpus: The British National Corpus.
            """
            [...]

     -  **Corpora:**

        * Bob's wordlist.
        * The British National Corpus.

.. Note:: The module-level variable ``__extra_epydoc_fields__`` is deprecated;
          use ``@newfield`` instead.
