Close #4257: autodoc: Add autodoc_class_signature

Add `autodoc_class_signature` to separate the class entry and the
definition of `__init__()` method.

5 files changed, 116 insertions, 0 deletions

diff --git a/CHANGES b/CHANGES
index 3ef0bb53e..da8580fe6 100644
--- a/CHANGES
+++ b/CHANGES
@@ -28,6 +28,8 @@ Features added
 * #9195: autodoc: The arguments of ``typing.Literal`` are wrongly rendered
 * #9185: autodoc: :confval:`autodoc_typehints` allows ``'both'`` setting to
   allow typehints to be included both in the signature and description
+* #4257: autodoc: Add :confval:`autodoc_class_signature` to separate the class
+  entry and the definition of ``__init__()`` method
 * #3257: autosummary: Support instance attributes for classes
 * #9129: html search: Show search summaries when html_copy_source = False
 * #9120: html theme: Eliminate prompt characters of code-block from copyable
diff --git a/doc/usage/extensions/autodoc.rst b/doc/usage/extensions/autodoc.rst
index e547e698b..2c9e19a8e 100644
--- a/doc/usage/extensions/autodoc.rst
+++ b/doc/usage/extensions/autodoc.rst
@@ -463,6 +463,20 @@ There are also config values that you can set:
 
    .. versionadded:: 1.4
 
+.. confval:: autodoc_class_signature
+
+   This value selects how the signautre will be displayed for the class defined
+   by :rst:dir:`autoclass` directive.  The possible values are:
+
+   ``"mixed"``
+      Display the signature with the class name.
+   ``"separated"``
+      Display the signature as a method.
+
+   The default is ``"mixed"``.
+
+   .. versionadded:: 4.1
+
 .. confval:: autodoc_member_order
 
    This value selects if automatically documented members are sorted
diff --git a/sphinx/ext/autodoc/__init__.py b/sphinx/ext/autodoc/__init__.py
index c64496139..1f4c98284 100644
--- a/sphinx/ext/autodoc/__init__.py
+++ b/sphinx/ext/autodoc/__init__.py
@@ -70,6 +70,9 @@ class _All:
     def __contains__(self, item: Any) -> bool:
         return True
 
+    def append(self, item: Any) -> None:
+        pass  # nothing
+
 
 class _Empty:
     """A special value for :exclude-members: that never matches to any member."""
@@ -1440,6 +1443,15 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
 
     def __init__(self, *args: Any) -> None:
         super().__init__(*args)
+
+        if self.config.autodoc_class_signature == 'separated':
+            # show __init__() method
+            if self.options.special_members is None:
+                self.options['special-members'] = {'__new__', '__init__'}
+            else:
+                self.options.special_members.append('__new__')
+                self.options.special_members.append('__init__')
+
         merge_members_option(self.options)
 
     @classmethod
@@ -1556,6 +1568,9 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
     def format_signature(self, **kwargs: Any) -> str:
         if self.doc_as_attr:
             return ''
+        if self.config.autodoc_class_signature == 'separated':
+            # do not show signatures
+            return ''
 
         sig = super().format_signature()
         sigs = []
@@ -2193,6 +2208,38 @@ class MethodDocumenter(DocstringSignatureMixin, ClassLevelDocumenter):  # type:
         else:
             return None
 
+    def get_doc(self, ignore: int = None) -> Optional[List[List[str]]]:
+        if self.objpath[-1] == '__init__':
+            docstring = getdoc(self.object, self.get_attr,
+                               self.config.autodoc_inherit_docstrings,
+                               self.parent, self.object_name)
+            if (docstring is not None and
+                (docstring == object.__init__.__doc__ or  # for pypy
+                 docstring.strip() == object.__init__.__doc__)):  # for !pypy
+                docstring = None
+            if docstring:
+                tab_width = self.directive.state.document.settings.tab_width
+                return [prepare_docstring(docstring, tabsize=tab_width)]
+            else:
+                return []
+        elif self.objpath[-1] == '__new__':
+            __new__ = self.get_attr(self.object, '__new__', None)
+            if __new__:
+                docstring = getdoc(__new__, self.get_attr,
+                                   self.config.autodoc_inherit_docstrings,
+                                   self.parent, self.object_name)
+                if (docstring is not None and
+                    (docstring == object.__new__.__doc__ or  # for pypy
+                     docstring.strip() == object.__new__.__doc__)):  # for !pypy
+                    docstring = None
+            if docstring:
+                tab_width = self.directive.state.document.settings.tab_width
+                return [prepare_docstring(docstring, tabsize=tab_width)]
+            else:
+                return []
+        else:
+            return super().get_doc()
+
 
 class NonDataDescriptorMixin(DataDocumenterMixinBase):
     """
@@ -2662,6 +2709,7 @@ def setup(app: Sphinx) -> Dict[str, Any]:
     app.add_config_value('autoclass_content', 'class', True, ENUM('both', 'class', 'init'))
     app.add_config_value('autodoc_member_order', 'alphabetical', True,
                          ENUM('alphabetic', 'alphabetical', 'bysource', 'groupwise'))
+    app.add_config_value('autodoc_class_signature', 'mixed', True, ENUM('mixed', 'separated'))
     app.add_config_value('autodoc_default_options', {}, True)
     app.add_config_value('autodoc_docstring_signature', True, True)
     app.add_config_value('autodoc_mock_imports', [], True)
diff --git a/sphinx/ext/autosummary/__init__.py b/sphinx/ext/autosummary/__init__.py
index be9f0cc65..0bf921f0b 100644
--- a/sphinx/ext/autosummary/__init__.py
+++ b/sphinx/ext/autosummary/__init__.py
@@ -174,6 +174,7 @@ class FakeDirective(DocumenterBridge):
         document = Struct(settings=settings)
         env = BuildEnvironment()
         env.config = Config()
+        env.config.add('autodoc_class_signature', 'mixed', True, None)
         state = Struct(document=document)
         super().__init__(env, None, Options(), 0, state)
 
diff --git a/tests/test_ext_autodoc_configs.py b/tests/test_ext_autodoc_configs.py
index b9bed1635..e0f08ea77 100644
--- a/tests/test_ext_autodoc_configs.py
+++ b/tests/test_ext_autodoc_configs.py
@@ -141,6 +141,57 @@ def test_autoclass_content_init(app):
 
 
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_autodoc_class_signature_mixed(app):
+    app.config.autodoc_class_signature = 'mixed'
+    options = {"members": None,
+               "undoc-members": None}
+    actual = do_autodoc(app, 'class', 'target.classes.Bar', options)
+    assert list(actual) == [
+        '',
+        '.. py:class:: Bar(x, y)',
+        '   :module: target.classes',
+        '',
+    ]
+
+
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_autodoc_class_signature_separated_init(app):
+    app.config.autodoc_class_signature = 'separated'
+    options = {"members": None,
+               "undoc-members": None}
+    actual = do_autodoc(app, 'class', 'target.classes.Bar', options)
+    assert list(actual) == [
+        '',
+        '.. py:class:: Bar',
+        '   :module: target.classes',
+        '',
+        '',
+        '   .. py:method:: Bar.__init__(x, y)',
+        '      :module: target.classes',
+        '',
+    ]
+
+
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_autodoc_class_signature_separated_new(app):
+    app.config.autodoc_class_signature = 'separated'
+    options = {"members": None,
+               "undoc-members": None}
+    actual = do_autodoc(app, 'class', 'target.classes.Baz', options)
+    assert list(actual) == [
+        '',
+        '.. py:class:: Baz',
+        '   :module: target.classes',
+        '',
+        '',
+        '   .. py:method:: Baz.__new__(cls, x, y)',
+        '      :module: target.classes',
+        '      :staticmethod:',
+        '',
+    ]
+
+
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_autoclass_content_both(app):
     app.config.autoclass_content = 'both'
     options = {"members": None}