Support PEP 695 and PEP 696 syntax in the Python domain (#11444)

* Generic classes can be documented with ``.. py:class::`` using PEP 695 syntax:

  .. code:: rst

     .. py:class:: Sequence[T]

* Generic functions can be documented with ``.. py:function::`` using PEP 695 syntax:

  .. code:: rst

     .. py:function:: foo[T](x: T)

* Default values for type bounds are supported.

Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>

CHANGES

@@ -34,6 +34,12 @@ Features added
 * #11157: Keep the ``translated`` attribute on translated nodes.
 * #11451: Improve the traceback displayed when using :option:`sphinx-build -T`
   in parallel builds. Patch by Bénédikt Tran
+* #11438: Add support for the :rst:dir:`py:class` and :rst:dir:`py:function`
+  directives for PEP 695 (generic classes and functions declarations) and
+  PEP 696 (default type parameters).  Multi-line support (#11011) is enabled
+  for type parameters list and can be locally controlled on object description
+  directives, e.g., :rst:dir:`py:function:single-line-type-parameter-list`.
+  Patch by Bénédikt Tran.
 
 Bugs fixed
 ----------

doc/latex.rst

@@ -1464,6 +1464,7 @@ Macros
      ``\sphinxtermref``;        ``\emph{#1}``
      ``\sphinxsamedocref``;     ``\emph{#1}``
      ``\sphinxparam``;          ``\emph{#1}``
+     ``\sphinxtypeparam``;      ``\emph{#1}``
      ``\sphinxoptional``; ``[#1]`` with larger brackets, see source
 
   .. versionadded:: 1.4.5
@@ -1485,6 +1486,12 @@ Macros
      signatures (see :confval:`maximum_signature_line_length`).  It defaults
      to ``\texttt{,}`` to make these end-of-line separators more distinctive.
 
+     Signatures of Python functions are rendered as ``name<space>(parameters)``
+     or ``name<space>[type parameters]<space>(parameters)`` (see :pep:`695`)
+     where the length of ``<space>`` is set to ``0pt`` by default.
+     This can be changed via ``\setlength{\sphinxsignaturelistskip}{1ex}``
+     for instance.
+
 - More text styling:
 
   .. csv-table::

doc/usage/configuration.rst

@@ -3025,9 +3025,24 @@ Options for the Python domain
 
 .. confval:: python_maximum_signature_line_length
 
-   If a signature's length in characters exceeds the number set, each
-   argument will be displayed on an individual logical line. This is a
-   domain-specific setting, overriding :confval:`maximum_signature_line_length`.
+   If a signature's length in characters exceeds the number set,
+   each argument or type parameter will be displayed on an individual logical line.
+   This is a domain-specific setting,
+   overriding :confval:`maximum_signature_line_length`.
+
+   For the Python domain, the signature length depends on whether
+   the type parameters or the list of arguments are being formatted.
+   For the former, the signature length ignores the length of the arguments list;
+   for the latter, the signature length ignores the length of
+   the type parameters list.
+
+   For instance, with `python_maximum_signature_line_length = 20`,
+   only the list of type parameters will be wrapped
+   while the arguments list will be rendered on a single line
+
+   .. code:: rst
+
+      .. py:function:: add[T: VERY_LONG_SUPER_TYPE, U: VERY_LONG_SUPER_TYPE](a: T, b: U)
 
    .. versionadded:: 7.1
 

doc/usage/restructuredtext/domains.rst

@@ -192,12 +192,16 @@ declarations:
 The following directives are provided for module and class contents:
 
 .. rst:directive:: .. py:function:: name(parameters)
+                   .. py:function:: name[type parameters](parameters)
 
-   Describes a module-level function.  The signature should include the
-   parameters as given in the Python function definition, see :ref:`signatures`.
+   Describes a module-level function.
+   The signature should include the parameters,
+   together with optional type parameters,
+   as given in the Python function definition, see :ref:`signatures`.
    For example::
 
-      .. py:function:: Timer.repeat(repeat=3, number=1000000)
+      .. py:function:: Timer.repeat(repeat=3, number=1_000_000)
+      .. py:function:: add[T](a: T, b: T) -> T
 
    For methods you should use :rst:dir:`py:method`.
 
@@ -240,6 +244,15 @@ The following directives are provided for module and class contents:
 
       .. versionadded:: 7.1
 
+   .. rst:directive:option:: single-line-type-parameter-list
+      :type: no value
+
+      Ensure that the function's type parameters are emitted on a single
+      logical line, overriding :confval:`python_maximum_signature_line_length`
+      and :confval:`maximum_signature_line_length`.
+
+      .. versionadded:: 7.1
+
 
 .. rst:directive:: .. py:data:: name
 
@@ -274,9 +287,12 @@ The following directives are provided for module and class contents:
       the module specified by :rst:dir:`py:currentmodule`.
 
 .. rst:directive:: .. py:exception:: name
+                   .. py:exception:: name(parameters)
+                   .. py:exception:: name[type parmeters](parameters)
 
-   Describes an exception class.  The signature can, but need not include
-   parentheses with constructor arguments.
+   Describes an exception class.
+   The signature can, but need not include parentheses with constructor arguments,
+   or may optionally include type parameters (see :pep:`695`).
 
    .. rubric:: options
 
@@ -293,12 +309,28 @@ The following directives are provided for module and class contents:
       Describe the location where the object is defined.  The default value is
       the module specified by :rst:dir:`py:currentmodule`.
 
+   .. rst:directive:option:: single-line-parameter-list
+      :type: no value
+
+      See :rst:dir:`py:class:single-line-parameter-list`.
+
+      .. versionadded:: 7.1
+
+   .. rst:directive:option:: single-line-type-parameter-list
+      :type: no value
+
+      See :rst:dir:`py:class:single-line-type-parameter-list`.
+
+      .. versionadded:: 7.1
+
 .. rst:directive:: .. py:class:: name
                    .. py:class:: name(parameters)
+                   .. py:class:: name[type parmeters](parameters)
 
-   Describes a class.  The signature can optionally include parentheses with
-   parameters which will be shown as the constructor arguments.  See also
-   :ref:`signatures`.
+   Describes a class.
+   The signature can optionally include type parameters (see :pep:`695`)
+   or parentheses with parameters which will be shown as the constructor arguments.
+   See also :ref:`signatures`.
 
    Methods and attributes belonging to the class should be placed in this
    directive's body.  If they are placed outside, the supplied name should
@@ -348,6 +380,13 @@ The following directives are provided for module and class contents:
 
       .. versionadded:: 7.1
 
+   .. rst:directive:option:: single-line-type-parameter-list
+      :type: no value
+
+      Ensure that the class type parameters are emitted on a single logical
+      line, overriding :confval:`python_maximum_signature_line_length` and
+      :confval:`maximum_signature_line_length`.
+
 .. rst:directive:: .. py:attribute:: name
 
    Describes an object data attribute.  The description should include
@@ -410,6 +449,7 @@ The following directives are provided for module and class contents:
       the module specified by :rst:dir:`py:currentmodule`.
 
 .. rst:directive:: .. py:method:: name(parameters)
+                   .. py:method:: name[type parameters](parameters)
 
    Describes an object method.  The parameters should not include the ``self``
    parameter.  The description should include similar information to that
@@ -469,6 +509,15 @@ The following directives are provided for module and class contents:
 
       .. versionadded:: 7.1
 
+   .. rst:directive:option:: single-line-type-parameter-list
+      :type: no value
+
+      Ensure that the method's type parameters are emitted on a single logical
+      line, overriding :confval:`python_maximum_signature_line_length` and
+      :confval:`maximum_signature_line_length`.
+
+      .. versionadded:: 7.2
+
    .. rst:directive:option:: staticmethod
       :type: no value
 
@@ -478,19 +527,22 @@ The following directives are provided for module and class contents:
 
 
 .. rst:directive:: .. py:staticmethod:: name(parameters)
+                   .. py:staticmethod:: name[type parameters](parameters)
 
    Like :rst:dir:`py:method`, but indicates that the method is a static method.
 
    .. versionadded:: 0.4
 
 .. rst:directive:: .. py:classmethod:: name(parameters)
+                   .. py:classmethod:: name[type parameters](parameters)
 
    Like :rst:dir:`py:method`, but indicates that the method is a class method.
 
    .. versionadded:: 0.6
 
 .. rst:directive:: .. py:decorator:: name
                    .. py:decorator:: name(parameters)
+                   .. py:decorator:: name[type parameters](parameters)
 
    Describes a decorator function.  The signature should represent the usage as
    a decorator.  For example, given the functions
@@ -531,8 +583,18 @@ The following directives are provided for module and class contents:
 
       .. versionadded:: 7.1
 
+   .. rst:directive:option:: single-line-type-parameter-list
+      :type: no value
+
+      Ensure that the decorator's type parameters are emitted on a single
+      logical line, overriding :confval:`python_maximum_signature_line_length`
+      and :confval:`maximum_signature_line_length`.
+
+      .. versionadded:: 7.2
+
 .. rst:directive:: .. py:decoratormethod:: name
                    .. py:decoratormethod:: name(signature)
+                   .. py:decoratormethod:: name[type parameters](signature)
 
    Same as :rst:dir:`py:decorator`, but for decorators that are methods.
 
@@ -561,6 +623,27 @@ argument support), you can use brackets to specify the optional parts:
 
 It is customary to put the opening bracket before the comma.
 
+Python 3.12 introduced *type parameters*, which are type variables
+declared directly  within the class or function definition:
+
+.. code:: python
+
+   class AnimalList[AnimalT](list[AnimalT]):
+      ...
+
+   def add[T](a: T, b: T) -> T:
+      return a + b
+
+The corresponding reStructuredText documentation would be:
+
+.. code:: rst
+
+   .. py:class:: AnimalList[AnimalT]
+
+   .. py:function:: add[T](a: T, b: T) -> T
+
+See :pep:`695` and :pep:`696` for details and the full specification.
+
 .. _info-field-lists:
 
 Info field lists

sphinx/addnodes.py

@@ -258,10 +258,27 @@ def astext(self):
         return f'({super().astext()})'
 
 
+class desc_type_parameter_list(nodes.Part, nodes.Inline, nodes.FixedTextElement):
+    """Node for a general type parameter list.
+
+    As default the type parameters list is written in line with the rest of the signature.
+    Set ``multi_line_parameter_list = True`` to describe a multi-line type parameters list.
+    In that case each type parameter will then be written on its own, indented line.
+    """
+    child_text_separator = ', '
+
+    def astext(self):
+        return f'[{super().astext()}]'
+
+
 class desc_parameter(nodes.Part, nodes.Inline, nodes.FixedTextElement):
     """Node for a single parameter."""
 
 
+class desc_type_parameter(nodes.Part, nodes.Inline, nodes.FixedTextElement):
+    """Node for a single type parameter."""
+
+
 class desc_optional(nodes.Part, nodes.Inline, nodes.FixedTextElement):
     """Node for marking optional parts of the parameter list."""
     child_text_separator = ', '
@@ -537,7 +554,9 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.add_node(desc_type)
     app.add_node(desc_returns)
     app.add_node(desc_parameterlist)
+    app.add_node(desc_type_parameter_list)
     app.add_node(desc_parameter)
+    app.add_node(desc_type_parameter)
     app.add_node(desc_optional)
     app.add_node(desc_annotation)