Close #6518: autodoc: Add autodoc_type_aliases

autodoc_type_aliases allows to keep user defined type alises not
evaluated in the generated document.

6 files changed, 144 insertions, 16 deletions

diff --git a/doc/usage/extensions/autodoc.rst b/doc/usage/extensions/autodoc.rst
index 802be3bd0..2d8a216c0 100644
--- a/doc/usage/extensions/autodoc.rst
+++ b/doc/usage/extensions/autodoc.rst
@@ -515,6 +515,44 @@ There are also config values that you can set:
 
       New option ``'description'`` is added.
 
+.. confval:: autodoc_type_aliases
+
+   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.  Defaults to empty (``{}``).
+
+   The type aliases are only available if your program enables `Postponed
+   Evaluation of Annotations (PEP 563)`__ feature via ``from __future__ import
+   annotations``.
+
+   For example, there is code using a type alias::
+
+     from __future__ import annotations
+
+     AliasType = Union[List[Dict[Tuple[int, str], Set[int]]], Tuple[str, List[str]]]
+
+     def f() -> AliasType:
+         ...
+
+   If ``autodoc_type_aliases`` is not set, autodoc will generate internal mark-up
+   from this code as following::
+
+     .. py:function:: f() -> Union[List[Dict[Tuple[int, str], Set[int]]], Tuple[str, List[str]]]
+
+        ...
+
+   If you set ``autodoc_type_aliases`` as
+   ``{'AliasType': 'your.module.TypeAlias'}``, it generates a following document
+   internally::
+
+     .. py:function:: f() -> your.module.AliasType:
+
+        ...
+
+   .. __: https://www.python.org/dev/peps/pep-0563/
+   .. __: https://mypy.readthedocs.io/en/latest/kinds_of_types.html#type-aliases
+   .. versionadded:: 3.3
+
 .. confval:: autodoc_warningiserror
 
    This value controls the behavior of :option:`sphinx-build -W` during
diff --git a/sphinx/ext/autodoc/__init__.py b/sphinx/ext/autodoc/__init__.py
index 35bb1c90d..d7c5d2242 100644
--- a/sphinx/ext/autodoc/__init__.py
+++ b/sphinx/ext/autodoc/__init__.py
@@ -1213,7 +1213,8 @@ class FunctionDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # typ
 
         try:
             self.env.app.emit('autodoc-before-process-signature', self.object, False)
-            sig = inspect.signature(self.object, follow_wrapped=True)
+            sig = inspect.signature(self.object, follow_wrapped=True,
+                                    type_aliases=self.env.config.autodoc_type_aliases)
             args = stringify_signature(sig, **kwargs)
         except TypeError as exc:
             logger.warning(__("Failed to get a function signature for %s: %s"),
@@ -1262,7 +1263,9 @@ class FunctionDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # typ
         if overloaded:
             __globals__ = safe_getattr(self.object, '__globals__', {})
             for overload in self.analyzer.overloads.get('.'.join(self.objpath)):
-                overload = evaluate_signature(overload, __globals__)
+                overload = evaluate_signature(overload, __globals__,
+                                              self.env.config.autodoc_type_aliases)
+
                 sig = stringify_signature(overload, **kwargs)
                 sigs.append(sig)
 
@@ -1271,7 +1274,7 @@ class FunctionDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # typ
     def annotate_to_first_argument(self, func: Callable, typ: Type) -> None:
         """Annotate type hint to the first argument of function if needed."""
         try:
-            sig = inspect.signature(func)
+            sig = inspect.signature(func, type_aliases=self.env.config.autodoc_type_aliases)
         except TypeError as exc:
             logger.warning(__("Failed to get a function signature for %s: %s"),
                            self.fullname, exc)
@@ -1392,7 +1395,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
         if call is not None:
             self.env.app.emit('autodoc-before-process-signature', call, True)
             try:
-                sig = inspect.signature(call, bound_method=True)
+                sig = inspect.signature(call, bound_method=True,
+                                        type_aliases=self.env.config.autodoc_type_aliases)
                 return type(self.object), '__call__', sig
             except ValueError:
                 pass
@@ -1407,7 +1411,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
         if new is not None:
             self.env.app.emit('autodoc-before-process-signature', new, True)
             try:
-                sig = inspect.signature(new, bound_method=True)
+                sig = inspect.signature(new, bound_method=True,
+                                        type_aliases=self.env.config.autodoc_type_aliases)
                 return self.object, '__new__', sig
             except ValueError:
                 pass
@@ -1417,7 +1422,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
         if init is not None:
             self.env.app.emit('autodoc-before-process-signature', init, True)
             try:
-                sig = inspect.signature(init, bound_method=True)
+                sig = inspect.signature(init, bound_method=True,
+                                        type_aliases=self.env.config.autodoc_type_aliases)
                 return self.object, '__init__', sig
             except ValueError:
                 pass
@@ -1428,7 +1434,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
         # the signature from, so just pass the object itself to our hook.
         self.env.app.emit('autodoc-before-process-signature', self.object, False)
         try:
-            sig = inspect.signature(self.object, bound_method=False)
+            sig = inspect.signature(self.object, bound_method=False,
+                                    type_aliases=self.env.config.autodoc_type_aliases)
             return None, None, sig
         except ValueError:
             pass
@@ -1475,7 +1482,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
             method = safe_getattr(self._signature_class, self._signature_method_name, None)
             __globals__ = safe_getattr(method, '__globals__', {})
             for overload in self.analyzer.overloads.get(qualname):
-                overload = evaluate_signature(overload, __globals__)
+                overload = evaluate_signature(overload, __globals__,
+                                              self.env.config.autodoc_type_aliases)
 
                 parameters = list(overload.parameters.values())
                 overload = overload.replace(parameters=parameters[1:],
@@ -1820,11 +1828,13 @@ class MethodDocumenter(DocstringSignatureMixin, ClassLevelDocumenter):  # type:
             else:
                 if inspect.isstaticmethod(self.object, cls=self.parent, name=self.object_name):
                     self.env.app.emit('autodoc-before-process-signature', self.object, False)
-                    sig = inspect.signature(self.object, bound_method=False)
+                    sig = inspect.signature(self.object, bound_method=False,
+                                            type_aliases=self.env.config.autodoc_type_aliases)
                 else:
                     self.env.app.emit('autodoc-before-process-signature', self.object, True)
                     sig = inspect.signature(self.object, bound_method=True,
-                                            follow_wrapped=True)
+                                            follow_wrapped=True,
+                                            type_aliases=self.env.config.autodoc_type_aliases)
                 args = stringify_signature(sig, **kwargs)
         except TypeError as exc:
             logger.warning(__("Failed to get a method signature for %s: %s"),
@@ -1884,7 +1894,9 @@ class MethodDocumenter(DocstringSignatureMixin, ClassLevelDocumenter):  # type:
         if overloaded:
             __globals__ = safe_getattr(self.object, '__globals__', {})
             for overload in self.analyzer.overloads.get('.'.join(self.objpath)):
-                overload = evaluate_signature(overload, __globals__)
+                overload = evaluate_signature(overload, __globals__,
+                                              self.env.config.autodoc_type_aliases)
+
                 if not inspect.isstaticmethod(self.object, cls=self.parent,
                                               name=self.object_name):
                     parameters = list(overload.parameters.values())
@@ -1897,7 +1909,7 @@ class MethodDocumenter(DocstringSignatureMixin, ClassLevelDocumenter):  # type:
     def annotate_to_first_argument(self, func: Callable, typ: Type) -> None:
         """Annotate type hint to the first argument of function if needed."""
         try:
-            sig = inspect.signature(func)
+            sig = inspect.signature(func, type_aliases=self.env.config.autodoc_type_aliases)
         except TypeError as exc:
             logger.warning(__("Failed to get a method signature for %s: %s"),
                            self.fullname, exc)
@@ -2237,6 +2249,7 @@ def setup(app: Sphinx) -> Dict[str, Any]:
     app.add_config_value('autodoc_mock_imports', [], True)
     app.add_config_value('autodoc_typehints', "signature", True,
                          ENUM("signature", "description", "none"))
+    app.add_config_value('autodoc_type_aliases', {}, True)
     app.add_config_value('autodoc_warningiserror', True, True)
     app.add_config_value('autodoc_inherit_docstrings', True, True)
     app.add_event('autodoc-before-process-signature')
diff --git a/sphinx/util/inspect.py b/sphinx/util/inspect.py
index 37997e6b2..378174993 100644
--- a/sphinx/util/inspect.py
+++ b/sphinx/util/inspect.py
@@ -439,8 +439,8 @@ def _should_unwrap(subject: Callable) -> bool:
     return False
 
 
-def signature(subject: Callable, bound_method: bool = False, follow_wrapped: bool = False
-              ) -> inspect.Signature:
+def signature(subject: Callable, bound_method: bool = False, follow_wrapped: bool = False,
+              type_aliases: Dict = {}) -> inspect.Signature:
     """Return a Signature object for the given *subject*.
 
     :param bound_method: Specify *subject* is a bound method or not
@@ -470,7 +470,7 @@ def signature(subject: Callable, bound_method: bool = False, follow_wrapped: boo
 
     try:
         # Update unresolved annotations using ``get_type_hints()``.
-        annotations = typing.get_type_hints(subject)
+        annotations = typing.get_type_hints(subject, None, type_aliases)
         for i, param in enumerate(parameters):
             if isinstance(param.annotation, str) and param.name in annotations:
                 parameters[i] = param.replace(annotation=annotations[param.name])
diff --git a/sphinx/util/typing.py b/sphinx/util/typing.py
index d71ca1b2d..4dac3b695 100644
--- a/sphinx/util/typing.py
+++ b/sphinx/util/typing.py
@@ -63,7 +63,11 @@ def is_system_TypeVar(typ: Any) -> bool:
 def stringify(annotation: Any) -> str:
     """Stringify type annotation object."""
     if isinstance(annotation, str):
-        return annotation
+        if annotation.startswith("'") and annotation.endswith("'"):
+            # might be a double Forward-ref'ed type.  Go unquoting.
+            return annotation[1:-2]
+        else:
+            return annotation
     elif isinstance(annotation, TypeVar):  # type: ignore
         return annotation.__name__
     elif not annotation:
diff --git a/tests/roots/test-ext-autodoc/target/annotations.py b/tests/roots/test-ext-autodoc/target/annotations.py
new file mode 100644
index 000000000..667149b26
--- /dev/null
+++ b/tests/roots/test-ext-autodoc/target/annotations.py
@@ -0,0 +1,25 @@
+from __future__ import annotations
+from typing import overload
+
+
+myint = int
+
+
+def sum(x: myint, y: myint) -> myint:
+    """docstring"""
+    return x + y
+
+
+@overload
+def mult(x: myint, y: myint) -> myint:
+    ...
+
+
+@overload
+def mult(x: float, y: float) -> float:
+    ...
+
+
+def mult(x, y):
+    """docstring"""
+    return x, y
diff --git a/tests/test_ext_autodoc_configs.py b/tests/test_ext_autodoc_configs.py
index 3d0bfd395..7d51b7f0e 100644
--- a/tests/test_ext_autodoc_configs.py
+++ b/tests/test_ext_autodoc_configs.py
@@ -642,6 +642,54 @@ def test_autodoc_typehints_description_for_invalid_node(app):
     restructuredtext.parse(app, text)  # raises no error
 
 
+@pytest.mark.skipif(sys.version_info < (3, 7), reason='python 3.7+ is required.')
+@pytest.mark.sphinx('text', testroot='ext-autodoc')
+def test_autodoc_type_aliases(app):
+    # default
+    options = {"members": None}
+    actual = do_autodoc(app, 'module', 'target.annotations', options)
+    assert list(actual) == [
+        '',
+        '.. py:module:: target.annotations',
+        '',
+        '',
+        '.. py:function:: mult(x: int, y: int) -> int',
+        '                 mult(x: float, y: float) -> float',
+        '   :module: target.annotations',
+        '',
+        '   docstring',
+        '',
+        '',
+        '.. py:function:: sum(x: int, y: int) -> int',
+        '   :module: target.annotations',
+        '',
+        '   docstring',
+        '',
+    ]
+
+    # define aliases
+    app.config.autodoc_type_aliases = {'myint': 'myint'}
+    actual = do_autodoc(app, 'module', 'target.annotations', options)
+    assert list(actual) == [
+        '',
+        '.. py:module:: target.annotations',
+        '',
+        '',
+        '.. py:function:: mult(x: myint, y: myint) -> myint',
+        '                 mult(x: float, y: float) -> float',
+        '   :module: target.annotations',
+        '',
+        '   docstring',
+        '',
+        '',
+        '.. py:function:: sum(x: myint, y: myint) -> myint',
+        '   :module: target.annotations',
+        '',
+        '   docstring',
+        '',
+    ]
+
+
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_autodoc_default_options(app):
     # no settings