Initial support for PEP 695 type aliases

Signed-off-by: Martin Matous <[email protected]>

Author: mmatous

AUTHORS.rst

@@ -87,6 +87,7 @@ Contributors
 * Martin Larralde -- additional napoleon admonitions
 * Martin Liška -- option directive and role improvements
 * Martin Mahner -- nature theme
+* Martin Matouš -- initial support for PEP 695
 * Matthew Fernandez -- todo extension fix
 * Matthew Woodcraft -- text output improvements
 * Matthias Geier -- style improvements

CHANGES.rst

@@ -19,6 +19,8 @@ Features added
 * #13439: linkcheck: Permit warning on every redirect with
   ``linkcheck_allowed_redirects = {}``.
   Patch by Adam Turner.
+* #13508: Initial support for PEP 695 type aliases.
+  Patch by Martin Matouš.
 
 Bugs fixed
 ----------

sphinx/ext/autodoc/__init__.py

@@ -54,6 +54,11 @@
         [Sphinx, _AutodocObjType, str, Any, dict[str, bool], list[str]], None
     ]
 
+if sys.version_info[:2] < (3, 12):
+    from typing_extensions import TypeAliasType
+else:
+    from typing import TypeAliasType
+
 logger = logging.getLogger(__name__)
 
 
@@ -1693,7 +1698,7 @@ def can_document_member(
         cls: type[Documenter], member: Any, membername: str, isattr: bool, parent: Any
     ) -> bool:
         return isinstance(member, type) or (
-            isattr and isinstance(member, NewType | TypeVar)
+            isattr and isinstance(member, NewType | TypeVar | TypeAliasType)
         )
 
     def import_object(self, raiseerror: bool = False) -> bool:
@@ -1705,7 +1710,7 @@ def import_object(self, raiseerror: bool = False) -> bool:
                 self.doc_as_attr = self.objpath[-1] != self.object.__name__
             else:
                 self.doc_as_attr = True
-            if isinstance(self.object, NewType | TypeVar):
+            if isinstance(self.object, NewType | TypeVar | TypeAliasType):
                 modname = getattr(self.object, '__module__', self.modname)
                 if modname != self.modname and self.modname.startswith(modname):
                     bases = self.modname[len(modname) :].strip('.').split('.')
@@ -1714,7 +1719,7 @@ def import_object(self, raiseerror: bool = False) -> bool:
         return ret
 
     def _get_signature(self) -> tuple[Any | None, str | None, Signature | None]:
-        if isinstance(self.object, NewType | TypeVar):
+        if isinstance(self.object, NewType | TypeVar | TypeAliasType):
             # Suppress signature
             return None, None, None
 
@@ -1925,6 +1930,8 @@ def add_directive_header(self, sig: str) -> None:
 
         if self.doc_as_attr:
             self.directivetype = 'attribute'
+        if isinstance(self.object, TypeAliasType):
+            self.directivetype = 'type'
         super().add_directive_header(sig)
 
         if isinstance(self.object, NewType | TypeVar):
@@ -1942,6 +1949,11 @@ def add_directive_header(self, sig: str) -> None:
         ):
             self.add_line('   :canonical: %s' % canonical_fullname, sourcename)
 
+        if isinstance(self.object, TypeAliasType):
+            aliased = stringify_annotation(self.object.__value__)
+            self.add_line('   :canonical: %s' % aliased, sourcename)
+            return
+
         # add inheritance info, if wanted
         if not self.doc_as_attr and self.options.show_inheritance:
             if inspect.getorigbases(self.object):

sphinx/pycode/parser.py

@@ -9,6 +9,7 @@
 import itertools
 import operator
 import re
+import sys
 import tokenize
 from token import DEDENT, INDENT, NAME, NEWLINE, NUMBER, OP, STRING
 from tokenize import COMMENT, NL
@@ -338,6 +339,47 @@ def get_line(self, lineno: int) -> str:
         """Returns specified line."""
         return self.buffers[lineno - 1]
 
+    def collect_doc_comment(
+        self,
+        # exists for >= 3.12, irrelevant for runtime
+        node: ast.Assign | ast.TypeAlias,  # type: ignore[name-defined]
+        varnames: list[str],
+        current_line: str,
+    ) -> None:
+        # check comments after assignment
+        parser = AfterCommentParser(
+            [current_line[node.col_offset :]] + self.buffers[node.lineno :]
+        )
+        parser.parse()
+        if parser.comment and comment_re.match(parser.comment):
+            for varname in varnames:
+                self.add_variable_comment(
+                    varname, comment_re.sub('\\1', parser.comment)
+                )
+                self.add_entry(varname)
+            return
+
+        # check comments before assignment
+        if indent_re.match(current_line[: node.col_offset]):
+            comment_lines = []
+            for i in range(node.lineno - 1):
+                before_line = self.get_line(node.lineno - 1 - i)
+                if comment_re.match(before_line):
+                    comment_lines.append(comment_re.sub('\\1', before_line))
+                else:
+                    break
+
+            if comment_lines:
+                comment = dedent_docstring('\n'.join(reversed(comment_lines)))
+                for varname in varnames:
+                    self.add_variable_comment(varname, comment)
+                    self.add_entry(varname)
+                return
+
+        # not commented (record deforders only)
+        for varname in varnames:
+            self.add_entry(varname)
+
     def visit(self, node: ast.AST) -> None:
         """Updates self.previous to the given node."""
         super().visit(node)
@@ -385,52 +427,19 @@ def visit_Assign(self, node: ast.Assign) -> None:
         elif hasattr(node, 'type_comment') and node.type_comment:
             for varname in varnames:
                 self.add_variable_annotation(varname, node.type_comment)  # type: ignore[arg-type]
-
-        # check comments after assignment
-        parser = AfterCommentParser(
-            [current_line[node.col_offset :]] + self.buffers[node.lineno :]
-        )
-        parser.parse()
-        if parser.comment and comment_re.match(parser.comment):
-            for varname in varnames:
-                self.add_variable_comment(
-                    varname, comment_re.sub('\\1', parser.comment)
-                )
-                self.add_entry(varname)
-            return
-
-        # check comments before assignment
-        if indent_re.match(current_line[: node.col_offset]):
-            comment_lines = []
-            for i in range(node.lineno - 1):
-                before_line = self.get_line(node.lineno - 1 - i)
-                if comment_re.match(before_line):
-                    comment_lines.append(comment_re.sub('\\1', before_line))
-                else:
-                    break
-
-            if comment_lines:
-                comment = dedent_docstring('\n'.join(reversed(comment_lines)))
-                for varname in varnames:
-                    self.add_variable_comment(varname, comment)
-                    self.add_entry(varname)
-                return
-
-        # not commented (record deforders only)
-        for varname in varnames:
-            self.add_entry(varname)
+        self.collect_doc_comment(node, varnames, current_line)
 
     def visit_AnnAssign(self, node: ast.AnnAssign) -> None:
         """Handles AnnAssign node and pick up a variable comment."""
         self.visit_Assign(node)  # type: ignore[arg-type]
 
     def visit_Expr(self, node: ast.Expr) -> None:
         """Handles Expr node and pick up a comment if string."""
-        if (
-            isinstance(self.previous, ast.Assign | ast.AnnAssign)
-            and isinstance(node.value, ast.Constant)
-            and isinstance(node.value.value, str)
+        if not (
+            isinstance(node.value, ast.Constant) and isinstance(node.value.value, str)
         ):
+            return
+        if isinstance(self.previous, ast.Assign | ast.AnnAssign):
             try:
                 targets = get_assign_targets(self.previous)
                 varnames = get_lvar_names(targets[0], self.get_self())
@@ -444,6 +453,13 @@ def visit_Expr(self, node: ast.Expr) -> None:
                     self.add_entry(varname)
             except TypeError:
                 pass  # this assignment is not new definition!
+        if (sys.version_info[:2] >= (3, 12)) and isinstance(
+            self.previous, ast.TypeAlias
+        ):
+            varname = self.previous.name.id
+            docstring = node.value.value
+            self.add_variable_comment(varname, dedent_docstring(docstring))
+            self.add_entry(varname)
 
     def visit_Try(self, node: ast.Try) -> None:
         """Handles Try node and processes body and else-clause.
@@ -488,6 +504,16 @@ def visit_AsyncFunctionDef(self, node: ast.AsyncFunctionDef) -> None:
         """Handles AsyncFunctionDef node and set context."""
         self.visit_FunctionDef(node)  # type: ignore[arg-type]
 
+    if sys.version_info[:2] >= (3, 12):
+        def visit_TypeAlias(self, node: ast.TypeAlias) -> None:
+            """Handles TypeAlias node and picks up a variable comment.
+
+            .. note:: TypeAlias node refers to `type Foo = Bar` (PEP 695) assignment,
+                      NOT `Foo: TypeAlias = Bar` (PEP 613).
+            """
+            current_line = self.get_line(node.lineno)
+            self.collect_doc_comment(node, [node.name.id], current_line)
+
 
 class DefinitionFinder(TokenProcessor):
     """Python source code parser to detect location of functions,

sphinx/util/typing.py

@@ -33,6 +33,11 @@
         'smart',
     ]
 
+if sys.version_info[:2] < (3, 12):
+    from typing_extensions import TypeAliasType
+else:
+    from typing import TypeAliasType
+
 logger = logging.getLogger(__name__)
 
 
@@ -309,6 +314,8 @@ def restify(cls: Any, mode: _RestifyMode = 'fully-qualified-except-typing') -> s
             # are printed natively and ``None``-like types are kept as is.
             # *cls* is defined in ``typing``, and thus ``__args__`` must exist
             return ' | '.join(restify(a, mode) for a in cls.__args__)
+        elif isinstance(cls, TypeAliasType):
+            return f':py:type:`{module_prefix}{cls.__module__}.{cls.__name__}`'
         elif cls.__module__ in {'__builtin__', 'builtins'}:
             if hasattr(cls, '__args__'):
                 if not cls.__args__:  # Empty tuple, list, ...
@@ -440,7 +447,9 @@ def stringify_annotation(
         annotation_module_is_typing = True
 
     # Extract the annotation's base type by considering formattable cases
-    if isinstance(annotation, typing.TypeVar) and not _is_unpack_form(annotation):
+    if isinstance(annotation, typing.TypeVar | TypeAliasType) and not _is_unpack_form(
+        annotation
+    ):
         # typing_extensions.Unpack is incorrectly determined as a TypeVar
         if annotation_module_is_typing and mode in {
             'fully-qualified-except-typing',

tests/test_extensions/test_ext_autodoc.py

@@ -2447,6 +2447,72 @@ def test_autodoc_GenericAlias(app):
     ]
 
 
+@pytest.mark.skipif(
+    sys.version_info[:2] < (3, 12),
+    reason='PEP 695 is Python 3.12 feature. Older versions fail to parse source into AST.',
+)
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_autodoc_Pep695Alias(app):
+    options = {
+        'members': None,
+        'undoc-members': None,
+    }
+    actual = do_autodoc(app, 'module', 'target.pep695', options)
+    assert list(actual) == [
+        '',
+        '.. py:module:: target.pep695',
+        '',
+        '',
+        '.. py:class:: Bar',
+        '   :module: target.pep695',
+        '',
+        '   This is newtype of Pep695Alias.',
+        '',
+        '   alias of :py:type:`~target.pep695.Pep695Alias`',
+        '',
+        '',
+        '.. py:class:: Foo()',
+        '   :module: target.pep695',
+        '',
+        '   This is class Foo.',
+        '',
+        '',
+        '.. py:type:: Pep695Alias',
+        '   :module: target.pep695',
+        '   :canonical: target.pep695.Foo',
+        '',
+        '   This is PEP695 type alias.',
+        '',
+        '',
+        '.. py:type:: Pep695AliasC',
+        '   :module: target.pep695',
+        '   :canonical: dict[str, target.pep695.Foo]',
+        '',
+        '   This is PEP695 complex type alias with doc comment.',
+        '',
+        '',
+        '.. py:type:: Pep695AliasOfAlias',
+        '   :module: target.pep695',
+        '   :canonical: target.pep695.Pep695AliasC',
+        '',
+        '   This is PEP695 type alias of PEP695 alias.',
+        '',
+        '',
+        '.. py:type:: Pep695AliasUnion',
+        '   :module: target.pep695',
+        '   :canonical: str | int',
+        '',
+        '   This is PEP695 type alias for union.',
+        '',
+        '',
+        '.. py:function:: ret_pep695(a: ~target.pep695.Pep695Alias) -> ~target.pep695.Pep695Alias',
+        '   :module: target.pep695',
+        '',
+        '   This fn accepts and returns PEP695 alias.',
+        '',
+    ]
+
+
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_autodoc_TypeVar(app):
     options = {