Fix autodoc_type_aliases when they appear in PEP 604 union syntax (Alias | Type)

Fix #14004

Author: taminomara

AUTHORS.rst

@@ -109,6 +109,7 @@ Contributors
 * Szymon Karpinski -- intersphinx improvements
 * \T. Powers -- HTML output improvements
 * Taku Shimizu -- epub3 builder
+* Tamika Nomara -- bug fixes
 * Thomas Lamb -- linkcheck builder
 * Thomas Waldmann -- apidoc module fixes
 * Till Hoffmann -- doctest option to exit after first failed test

CHANGES.rst

@@ -134,6 +134,8 @@ Bugs fixed
   Patch by Jeremy Maitin-Shepard.
 * #13939: LaTeX: page break can separate admonition title from contents.
   Patch by Jean-François B.
+* #14004: Fix `autodoc_type_aliases` when they appear in PEP 604 union syntax (`Alias | Type`).
+  Patch by Tamika Nomara.
 
 
 Testing

sphinx/util/inspect.py

@@ -616,6 +616,14 @@ def __hash__(self) -> int:
     def __repr__(self) -> str:
         return f'{self.__class__.__name__}({self.name!r})'
 
+    def __or__(self, value: Any):
+        # When evaluating type hints, our forward ref can appear in type expressions,
+        # i.e. `Alias | None`. It should, therefore, support `__or__` and `__ror__`.
+        return typing.Union[self, value]
+
+    def __ror__(self, value: Any):
+        return typing.Union[value, self]
+
 
 class TypeAliasModule:
     """Pseudo module class for :confval:`autodoc_type_aliases`."""

tests/test_util/test_util_inspect.py

@@ -115,6 +115,14 @@ def test_TypeAliasForwardRef():
     sig_str = stringify_annotation(alias, 'fully-qualified-except-typing')
     assert sig_str == "TypeAliasForwardRef('example') | None"
 
+    alias = alias | None
+    sig_str = stringify_annotation(alias, 'fully-qualified-except-typing')
+    assert sig_str == "TypeAliasForwardRef('example') | None"
+
+    alias = None | alias
+    sig_str = stringify_annotation(alias, 'fully-qualified-except-typing')
+    assert sig_str == "None | TypeAliasForwardRef('example')"
+
 
 def test_TypeAliasNamespace() -> None:
     import logging.config