Fix ``missing-function-docstring`` not checking ``__init__`` (#5147)

* Fix ``missing-function-docstring`` not checking ``__init__``

* Ignore ``object``

4 files changed, 52 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 333dd722c..f9eba4227 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -65,6 +65,9 @@ Release date: TBA
 
   Closes #3031
 
+* Fix ``missing-function-docstring`` not being able to check ``__init__`` and other
+  magic methods even if the ``no-docstring-rgx`` setting was set to do so
+
 
 What's New in Pylint 2.11.2?
 ============================
diff --git a/pylint/checkers/base.py b/pylint/checkers/base.py
index 5507bde74..699f2dae1 100644
--- a/pylint/checkers/base.py
+++ b/pylint/checkers/base.py
@@ -2192,6 +2192,8 @@ class DocStringChecker(_BasicChecker):
                 )
                 # check if node is from a method overridden by its ancestor
                 for ancestor in node.parent.frame().ancestors():
+                    if ancestor.qname() == "builtins.object":
+                        continue
                     if node.name in ancestor and isinstance(
                         ancestor[node.name], nodes.FunctionDef
                     ):
diff --git a/pylintrc b/pylintrc
index 376fb828e..b4a4e9fac 100644
--- a/pylintrc
+++ b/pylintrc
@@ -257,7 +257,7 @@ method-rgx=[a-z_][a-z0-9_]{2,}$
 method-name-hint=[a-z_][a-z0-9_]{2,}$
 
 # Regular expression which should only match function or class names that do
-# not require a docstring.
+# not require a docstring. Use ^(?!__init__$)_ to also check __init__.
 no-docstring-rgx=__.*__
 
 # Minimum line length for functions/classes that require docstrings, shorter
diff --git a/tests/checkers/unittest_base.py b/tests/checkers/unittest_base.py
index 48b48a450..616a0a8e7 100644
--- a/tests/checkers/unittest_base.py
+++ b/tests/checkers/unittest_base.py
@@ -58,6 +58,21 @@ class TestDocstring(CheckerTestCase):
         with self.assertAddsMessages(message):
             self.checker.visit_module(module)
 
+    @set_config(no_docstring_rgx=re.compile("^(?!__init__$)_"))
+    def test_empty_docstring_on_init(self) -> None:
+        node = astroid.extract_node(
+            """
+        #pylint disable=missing-module-docstring, too-few-public-methods,
+        class MyClass:
+            def __init__(self, my_param: int) -> None:
+                '''
+                '''
+        """
+        )
+        message = MessageTest("empty-docstring", node=node.body[0], args=("method",))
+        with self.assertAddsMessages(message):
+            self.checker.visit_functiondef(node.body[0])
+
     def test_empty_docstring_function(self) -> None:
         func = astroid.extract_node(
             """
@@ -116,6 +131,37 @@ class TestDocstring(CheckerTestCase):
         with self.assertNoMessages():
             self.checker.visit_functiondef(func)
 
+    @set_config(no_docstring_rgx=re.compile("^(?!__init__$)_"))
+    def test_missing_docstring_on_init(self) -> None:
+        node = astroid.extract_node(
+            """
+        #pylint disable=missing-module-docstring, too-few-public-methods,
+        class MyClass:
+            def __init__(self, my_param: int) -> None:
+                pass
+        """
+        )
+        message = MessageTest("missing-function-docstring", node=node.body[0])
+        with self.assertAddsMessages(message):
+            self.checker.visit_functiondef(node.body[0])
+
+    @set_config(no_docstring_rgx=re.compile("^(?!__eq__$)_"))
+    def test_missing_docstring_on_inherited_magic(self) -> None:
+        module = astroid.parse(
+            """
+        #pylint disable=missing-module-docstring, too-few-public-methods,
+        class MyClass:
+            pass
+
+        class Child(MyClass):
+            def __eq__(self, other):
+                return True
+        """
+        )
+        message = MessageTest("missing-function-docstring", node=module.body[1].body[0])
+        with self.assertAddsMessages(message):
+            self.checker.visit_functiondef(module.body[1].body[0])
+
     def test_class_no_docstring(self) -> None:
         klass = astroid.extract_node(
             """