Add support for recursive type hints (#248)

Co-authored-by: Mehdi Drissi <mdrissi@snapchat.com>

Author: hmc-cs-mdrissi

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 1.19.1
+
+- Fix bug for recursive type alias.
+
 ## 1.19.0
 
 - Support for CPython 3.11, no longer adds `Optional` when the argument is default per

src/sphinx_autodoc_typehints/__init__.py

@@ -5,7 +5,6 @@
 import sys
 import textwrap
 from ast import FunctionDef, Module, stmt
-from typing import _eval_type  # type: ignore # no import defined in stubs
 from typing import Any, AnyStr, Callable, ForwardRef, NewType, TypeVar, get_type_hints
 
 from sphinx.application import Sphinx
@@ -120,8 +119,7 @@ def format_annotation(annotation: Any, config: Config) -> str:  # noqa: C901 # t
 
     # Special cases
     if isinstance(annotation, ForwardRef):
-        value = _resolve_forward_ref(annotation, config)
-        return format_annotation(value, config)
+        return annotation.__forward_arg__
     if annotation is None or annotation is type(None):  # noqa: E721
         return ":py:obj:`None`"
     if annotation is Ellipsis:
@@ -195,17 +193,6 @@ def format_annotation(annotation: Any, config: Config) -> str:  # noqa: C901 # t
     return result
 
 
-def _resolve_forward_ref(annotation: ForwardRef, config: Config) -> Any:
-    raw, base_globals = annotation.__forward_arg__, config._annotation_globals
-    params = {"is_class": True} if (3, 10) > sys.version_info >= (3, 9, 8) or sys.version_info >= (3, 10, 1) else {}
-    value = ForwardRef(raw, is_argument=False, **params)
-    try:
-        result = _eval_type(value, base_globals, None)
-    except NameError:
-        result = raw  # fallback to the value itself as string
-    return result
-
-
 # reference: https://github.com/pytorch/pytorch/pull/46548/files
 def normalize_source_lines(source_lines: str) -> str:
     """

tests/test_sphinx_autodoc_typehints.py

@@ -15,6 +15,7 @@
     Callable,
     Dict,
     Generic,
+    List,
     Mapping,
     Match,
     NewType,
@@ -55,6 +56,12 @@
 S = TypeVar("S", bound="miss")  # type: ignore # miss not defined on purpose # noqa: F821
 W = NewType("W", str)
 
+# Mypy does not support recursive type aliases, but
+# other type checkers do.
+RecList = Union[int, List["RecList"]]  # type: ignore
+MutualRecA = Union[bool, List["MutualRecB"]]  # type: ignore
+MutualRecB = Union[str, List["MutualRecA"]]  # type: ignore
+
 
 class A:
     def get_type(self) -> type:
@@ -228,7 +235,7 @@ def test_parse_annotation(annotation: Any, module: str, class_name: str, args: t
         (V, ":py:class:`~typing.TypeVar`\\(``V``, contravariant=True)"),
         (X, ":py:class:`~typing.TypeVar`\\(``X``, :py:class:`str`, :py:class:`int`)"),
         (Y, ":py:class:`~typing.TypeVar`\\(``Y``, bound= :py:class:`str`)"),
-        (Z, ":py:class:`~typing.TypeVar`\\(``Z``, bound= :py:class:`~test_sphinx_autodoc_typehints.A`)"),
+        (Z, ":py:class:`~typing.TypeVar`\\(``Z``, bound= A)"),
         (S, ":py:class:`~typing.TypeVar`\\(``S``, bound= miss)"),
         # ## These test for correct internal tuple rendering, even if not all are valid Tuple types
         # Zero-length tuple remains
@@ -279,6 +286,14 @@ def test_parse_annotation(annotation: Any, module: str, class_name: str, args: t
                 "...], :py:class:`~numpy.float64`]"
             ),
         ),
+        (
+            RecList,
+            (":py:data:`~typing.Union`\\[:py:class:`int`, :py:class:`~typing.List`\\[RecList]]"),
+        ),
+        (
+            MutualRecA,
+            (":py:data:`~typing.Union`\\[:py:class:`bool`, :py:class:`~typing.List`\\[MutualRecB]]"),
+        ),
     ],
 )
 def test_format_annotation(inv: Inventory, annotation: Any, expected_result: str) -> None: