Fix issue #481

[nineteendo]

No description provided.

[hoodmane]

Please add a test.

[nineteendo]

What should I do with "Class Alias"? That's not a valid forward reference.

[hoodmane]

The documentation of autodoc-type-aliases says:

A dictionary for users defined type aliases that maps a type name to the full-qualified object name. It is used to keep type aliases not evaluated in the document.

https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#confval-autodoc_type_aliases

Class Alias isn't a fully qualified object name or even an identifier.

[hoodmane]

But I don't understand the problem or the fix very well @nineteendo could you explain a bit more?

[nineteendo]

1. Aliases are converted to sphinx.util.inspect.TypeAliasForwardRef
2. Alias | A is not supported.
3. This crashes typing.get_type_hints()
4. All annotations become strings.

I fixed this by creating a subclass that defines __or__(). (This might need to be fixed upstream)

[nineteendo]

Hmm, forward references are not subscriptable either:

WARNING: Cannot resolve forward reference in type annotations of "jsonyx.dump": 'MyTypeAliasForwardRef' object is
not subscriptable

[nineteendo]

Here a potential implementation for that (I've had enough of it):

diff --git a/src/sphinx_autodoc_typehints/__init__.py b/src/sphinx_autodoc_typehints/__init__.py
index 4f20b97..0231a91 100644
--- a/src/sphinx_autodoc_typehints/__init__.py
+++ b/src/sphinx_autodoc_typehints/__init__.py
@@ -65,6 +65,9 @@ class MyTypeAliasForwardRef(TypeAliasForwardRef):
     def __or__(self, value: Any) -> Any:
         return Union[self, value]  # noqa: UP007
 
+    def __getitem__(self, item: Any) -> types.GenericAlias:
+        return types.GenericAlias(self, item)  # type: ignore
+
 
 def _get_types_type(obj: Any) -> str | None:
     try:
@@ -227,9 +230,6 @@ def format_annotation(annotation: Any, config: Config, *, short_literals: bool =
     if isinstance(annotation, tuple):
         return format_internal_tuple(annotation, config)
 
-    if isinstance(annotation, TypeAliasForwardRef):
-        return annotation.name
-
     try:
         module = get_annotation_module(annotation)
         class_name = get_annotation_class_name(annotation, module)
@@ -300,6 +300,10 @@ def format_annotation(annotation: Any, config: Config, *, short_literals: bool =
         formatted_args = args_format.format(", ".join(fmt))
 
     escape = "\\ " if formatted_args else ""
+    annotation = getattr(annotation, "__origin__", annotation)
+    if isinstance(annotation, TypeAliasForwardRef):
+        return f"{annotation.name}{escape}{formatted_args}"
+
     return f":py:{role}:`{prefix}{full_name}`{escape}{formatted_args}"