Fix #8134: autodoc: crashes when mocked decorator takes arguments

autodoc crashed when a decorator in mocked module takes arguments
because mock system returns the first argument for the decorator as a
decorated object.

This changes the approach for mocking decorators that remembers
arguments for each decoration, and fetch the latest argument on
generating document.

3 files changed, 29 insertions, 8 deletions

diff --git a/sphinx/ext/autodoc/__init__.py b/sphinx/ext/autodoc/__init__.py
index 83c7d28c4..1490d1551 100644
--- a/sphinx/ext/autodoc/__init__.py
+++ b/sphinx/ext/autodoc/__init__.py
@@ -27,7 +27,7 @@ from sphinx.deprecation import (RemovedInSphinx40Warning, RemovedInSphinx50Warni
 from sphinx.environment import BuildEnvironment
 from sphinx.ext.autodoc.importer import (get_class_members, get_object_members, import_module,
                                          import_object)
-from sphinx.ext.autodoc.mock import ismock, mock
+from sphinx.ext.autodoc.mock import ismock, mock, undecorate
 from sphinx.locale import _, __
 from sphinx.pycode import ModuleAnalyzer, PycodeError
 from sphinx.util import inspect, logging
@@ -422,6 +422,8 @@ class Documenter:
                                     attrgetter=self.get_attr,
                                     warningiserror=self.config.autodoc_warningiserror)
                 self.module, self.parent, self.object_name, self.object = ret
+                if ismock(self.object):
+                    self.object = undecorate(self.object)
                 return True
             except ImportError as exc:
                 if raiseerror:
@@ -1054,6 +1056,8 @@ class ModuleDocumenter(Documenter):
         for name in dir(self.object):
             try:
                 value = safe_getattr(self.object, name, None)
+                if ismock(value):
+                    value = undecorate(value)
                 docstring = attr_docs.get(('', name), [])
                 members[name] = ObjectMember(name, value, docstring="\n".join(docstring))
             except AttributeError:
diff --git a/sphinx/ext/autodoc/importer.py b/sphinx/ext/autodoc/importer.py
index ffcb27ecc..d7c9b93f5 100644
--- a/sphinx/ext/autodoc/importer.py
+++ b/sphinx/ext/autodoc/importer.py
@@ -15,6 +15,7 @@ from typing import Any, Callable, Dict, List, Mapping, NamedTuple, Optional, Tup
 
 from sphinx.deprecation import (RemovedInSphinx40Warning, RemovedInSphinx50Warning,
                                 deprecated_alias)
+from sphinx.ext.autodoc.mock import ismock, undecorate
 from sphinx.pycode import ModuleAnalyzer, PycodeError
 from sphinx.util import logging
 from sphinx.util.inspect import (getannotations, getmro, getslots, isclass, isenumclass,
@@ -285,6 +286,9 @@ def get_class_members(subject: Any, objpath: List[str], attrgetter: Callable
     for name in dir(subject):
         try:
             value = attrgetter(subject, name)
+            if ismock(value):
+                value = undecorate(value)
+
             unmangled = unmangle(subject, name)
             if unmangled and unmangled not in members:
                 if name in obj_dict:
diff --git a/sphinx/ext/autodoc/mock.py b/sphinx/ext/autodoc/mock.py
index 3d4f76410..d3f4291c2 100644
--- a/sphinx/ext/autodoc/mock.py
+++ b/sphinx/ext/autodoc/mock.py
@@ -13,7 +13,7 @@ import os
 import sys
 from importlib.abc import Loader, MetaPathFinder
 from importlib.machinery import ModuleSpec
-from types import FunctionType, MethodType, ModuleType
+from types import ModuleType
 from typing import Any, Generator, Iterator, List, Sequence, Tuple, Union
 
 from sphinx.util import logging
@@ -27,6 +27,7 @@ class _MockObject:
 
     __display_name__ = '_MockObject'
     __sphinx_mock__ = True
+    __sphinx_decorator_args__ = ()  # type: Tuple[Any, ...]
 
     def __new__(cls, *args: Any, **kwargs: Any) -> Any:
         if len(args) == 3 and isinstance(args[1], tuple):
@@ -60,18 +61,19 @@ class _MockObject:
         return _make_subclass(key, self.__display_name__, self.__class__)()
 
     def __call__(self, *args: Any, **kwargs: Any) -> Any:
-        if args and type(args[0]) in [type, FunctionType, MethodType]:
-            # Appears to be a decorator, pass through unchanged
-            return args[0]
-        return self
+        call = self.__class__()
+        call.__sphinx_decorator_args__ = args
+        return call
 
     def __repr__(self) -> str:
         return self.__display_name__
 
 
 def _make_subclass(name: str, module: str, superclass: Any = _MockObject,
-                   attributes: Any = None) -> Any:
-    attrs = {'__module__': module, '__display_name__': module + '.' + name}
+                   attributes: Any = None, decorator_args: Tuple = ()) -> Any:
+    attrs = {'__module__': module,
+             '__display_name__': module + '.' + name,
+             '__sphinx_decorator_args__': decorator_args}
     attrs.update(attributes or {})
 
     return type(name, (superclass,), attrs)
@@ -172,3 +174,14 @@ def ismock(subject: Any) -> bool:
         pass
 
     return False
+
+
+def undecorate(subject: _MockObject) -> Any:
+    """Unwrap mock if *subject* is decorated by mocked object.
+
+    If not decorated, returns given *subject* itself.
+    """
+    if ismock(subject) and subject.__sphinx_decorator_args__:
+        return subject.__sphinx_decorator_args__[0]
+    else:
+        return subject