Support Union type on its own

Signed-off-by: Bernát Gábor <[email protected]>

Author: gaborbernat

src/sphinx_autodoc_typehints/__init__.py

@@ -300,6 +300,8 @@ def format_annotation(annotation: Any, config: Config, *, short_literals: bool =
             return f"\\{' | '.join(f'``{arg!r}``' for arg in args)}"
         formatted_args = f"\\[{', '.join(f'``{arg!r}``' for arg in args)}]"
     elif is_bars_union:
+        if not args:
+            return f":py:{'class' if sys.version_info >= (3, 14) else 'data'}:`{prefix}typing.Union`"
         return " | ".join([format_annotation(arg, config, short_literals=short_literals) for arg in args])
 
     if args and not formatted_args:

tests/test_sphinx_autodoc_typehints.py

@@ -244,7 +244,10 @@ def test_parse_annotation(annotation: Any, module: str, class_name: str, args: t
         r":py:data:`~typing.Tuple`\ \[:py:class:`str`, :py:data:`...<Ellipsis>`]",
         id="Tuple-str-Ellipsis",
     ),
-    pytest.param(Union, "" if sys.version_info >= (3, 14) else ":py:data:`~typing.Union`", id="Union"),
+    pytest.param(Union, f":py:{'class' if sys.version_info >= (3, 14) else 'data'}:`~typing.Union`", id="Union"),
+    pytest.param(
+        types.UnionType, f":py:{'class' if sys.version_info >= (3, 14) else 'data'}:`~typing.Union`", id="UnionType"
+    ),
     pytest.param(
         Union[str, bool],
         ":py:class:`str` | :py:class:`bool`"
@@ -280,6 +283,11 @@ def test_parse_annotation(annotation: Any, module: str, class_name: str, args: t
         else r":py:data:`~typing.Optional`\ \[:py:class:`str`]",
         id="Optional-str-None",
     ),
+    pytest.param(
+        type[T] | types.UnionType,
+        ":py:class:`type`\\ \\[:py:class:`~typing.TypeVar`\\ \\(``T``)] | :py:class:`~typing.Union`",
+        id="typevar union bar uniontype",
+    ),
     pytest.param(
         Optional[str | bool],
         ":py:class:`str` | :py:class:`bool` | :py:obj:`None`"