Fix sphinx-doc#8219: autodoc: A signature of constructor of generic c…

…lass is incorrect

Ignore the signature of typing.Generic.__new__() to get correct a
signature of the constructor from a subclass.

CHANGES

@@ -25,6 +25,7 @@ Bugs fixed
 * #8143: autodoc: AttributeError is raised when False value is passed to
   autodoc_default_options
 * #8103: autodoc: functools.cached_property is not considered as a property
+* #8219: autodoc: A signature of constructor of generic class is incorrect
 * #8192: napoleon: description is disappeared when it contains inline literals
 * #8169: LaTeX: pxjahyper loaded even when latex_engine is not platex
 * #8093: The highlight warning has wrong location in some builders (LaTeX,

sphinx/ext/autodoc/__init__.py

@@ -1312,13 +1312,17 @@ def format_args(self, **kwargs: Any) -> Any:
             return None
 
 
-# Types which have confusing metaclass signatures it would be best not to show.
-# These are listed by name, rather than storing the objects themselves, to avoid
-# needing to import the modules.
+# Types which have confusing metaclass signatures and superclass signatures it
+# would be best not to show.  These are listed by name, rather than storing the
+# objects themselves, to avoid needing to import the modules.
 _METACLASS_CALL_BLACKLIST = [
     'enum.EnumMeta.__call__',
 ]
 
+_SUPERCLASS_NEW_BLACKLIST = [
+    'typing.Generic.__new__',
+]
+
 
 class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type: ignore
     """
@@ -1388,6 +1392,11 @@ def get_user_defined_function_or_method(obj: Any, attr: str) -> Any:
 
         # Now we check if the 'obj' class has a '__new__' method
         new = get_user_defined_function_or_method(self.object, '__new__')
+
+        if new is not None:
+            if "{0.__module__}.{0.__qualname__}".format(new) in _SUPERCLASS_NEW_BLACKLIST:
+                new = None
+
         if new is not None:
             self.env.app.emit('autodoc-before-process-signature', new, True)
             try:

tests/roots/test-ext-autodoc/target/classes.py

@@ -1,3 +1,9 @@
+from typing import Generic, TypeVar
+
+
+T = TypeVar("T")
+
+
 class Foo:
     pass
 
@@ -10,3 +16,8 @@ def __init__(self, x, y):
 class Baz:
     def __new__(cls, x, y):
         pass
+
+
+class Qux(Generic[T]):
+    def __init__(self, x, y):
+        pass

tests/test_ext_autodoc_autoclass.py

@@ -0,0 +1,25 @@
+"""
+    test_ext_autodoc_autoclass
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    Test the autodoc extension.  This tests mainly the Documenters; the auto
+    directives are tested in a test source file translated by test_build.
+
+    :copyright: Copyright 2007-2020 by the Sphinx team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+import pytest
+
+from test_ext_autodoc import do_autodoc
+
+
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_generic_class(app):
+    actual = do_autodoc(app, 'class', 'target.classes.Qux')
+    assert list(actual) == [
+        '',
+        '.. py:class:: Qux(x, y)',
+        '   :module: target.classes',
+        '',
+    ]