[duplicate-code] Parse functions and class methods recursively when gathering signature lines (#4858)

* [duplicate-code] Parse functions and class methods recursively when gathering signature lines

7 files changed, 144 insertions, 5 deletions

diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index 80e68abb3..72d06f0a7 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -509,6 +509,7 @@ contributors:
 * Maksym Humetskyi (mhumetskyi): contributor
   - Fixed ignored empty functions by similarities checker with "ignore-signatures" option enabled
   - Ignore function decorators signatures as well by similarities checker with "ignore-signatures" option enabled
+  - Ignore class methods and nested functions signatures as well by similarities checker with "ignore-signatures" option enabled
 
 * Daniel Dorani (doranid): contributor
 
diff --git a/ChangeLog b/ChangeLog
index e5c4a5bae..6bd08a2d1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -150,6 +150,11 @@ Release date: TBA
 * Allow ``true`` and ``false`` values in ``pylintrc`` for better compatibility with ``toml`` config.
 
 
+* Class methods' signatures are ignored the same way as functions' with similarities "ignore-signatures" option enabled
+
+  Closes #4653
+
+
 What's New in Pylint 2.9.6?
 ===========================
 Release date: 2021-07-28
diff --git a/doc/whatsnew/2.10.rst b/doc/whatsnew/2.10.rst
index 7f2706de4..e8a354a05 100644
--- a/doc/whatsnew/2.10.rst
+++ b/doc/whatsnew/2.10.rst
@@ -105,3 +105,7 @@ Other Changes
 
 * Fixed bug with ``cell-var-from-loop`` checker: it no longer has false negatives when
   both ``unused-variable`` and ``used-before-assignment`` are disabled.
+
+* Class methods' signatures are now ignored the same way as functions' with similarities "ignore-signatures" option enabled
+
+  Closes #4653
diff --git a/pylint/checkers/similar.py b/pylint/checkers/similar.py
index 762ae35b2..b44081924 100644
--- a/pylint/checkers/similar.py
+++ b/pylint/checkers/similar.py
@@ -64,6 +64,7 @@ from typing import (
 )
 
 import astroid
+from astroid.node_classes import NodeNG
 
 from pylint.checkers import BaseChecker, MapReduceMixin, table_lines_from_stats
 from pylint.interfaces import IRawChecker
@@ -586,11 +587,23 @@ def stripped_lines(
         }
         current_line_is_import = False
     if ignore_signatures:
-        functions = [
-            n
-            for n in tree.body
-            if isinstance(n, (astroid.FunctionDef, astroid.AsyncFunctionDef))
-        ]
+
+        def _get_functions(functions: List[NodeNG], tree: NodeNG) -> List[NodeNG]:
+            """Recursively get all functions including nested in the classes from the tree."""
+
+            for node in tree.body:
+                if isinstance(node, (astroid.FunctionDef, astroid.AsyncFunctionDef)):
+                    functions.append(node)
+
+                if isinstance(
+                    node,
+                    (astroid.ClassDef, astroid.FunctionDef, astroid.AsyncFunctionDef),
+                ):
+                    _get_functions(functions, node)
+
+            return functions
+
+        functions = _get_functions([], tree)
         signature_lines = set(
             chain(
                 *(
diff --git a/tests/checkers/unittest_similar.py b/tests/checkers/unittest_similar.py
index ff3d92ddc..922fce654 100644
--- a/tests/checkers/unittest_similar.py
+++ b/tests/checkers/unittest_similar.py
@@ -36,6 +36,8 @@ SIMILAR3 = str(INPUT / "similar3")
 SIMILAR4 = str(INPUT / "similar4")
 SIMILAR5 = str(INPUT / "similar5")
 SIMILAR6 = str(INPUT / "similar6")
+SIMILAR_CLS_A = str(INPUT / "similar_cls_a.py")
+SIMILAR_CLS_B = str(INPUT / "similar_cls_b.py")
 EMPTY_FUNCTION_1 = str(INPUT / "similar_empty_func_1.py")
 EMPTY_FUNCTION_2 = str(INPUT / "similar_empty_func_2.py")
 MULTILINE = str(INPUT / "multiline-import")
@@ -213,6 +215,66 @@ TOTAL lines=35 duplicates=0 percent=0.00
     )
 
 
+def test_ignore_signatures_class_methods_fail():
+    output = StringIO()
+    with redirect_stdout(output), pytest.raises(SystemExit) as ex:
+        similar.Run([SIMILAR_CLS_B, SIMILAR_CLS_A])
+    assert ex.value.code == 0
+    assert (
+        output.getvalue().strip()
+        == (
+            '''
+15 similar lines in 2 files
+==%s:[1:18]
+==%s:[1:18]
+       def parent_method(
+           self,
+           *,
+           a="",
+           b=None,
+           c=True,
+       ):
+           """Overridden method example."""
+
+           def _internal_func(
+               arg1: int = 1,
+               arg2: str = "2",
+               arg3: int = 3,
+               arg4: bool = True,
+           ):
+               pass
+
+
+7 similar lines in 2 files
+==%s:[20:27]
+==%s:[20:27]
+               self,
+               *,
+               a=None,
+               b=False,
+               c="",
+           ):
+               pass
+TOTAL lines=54 duplicates=22 percent=40.74
+'''
+            % (SIMILAR_CLS_A, SIMILAR_CLS_B, SIMILAR_CLS_A, SIMILAR_CLS_B)
+        ).strip()
+    )
+
+
+def test_ignore_signatures_class_methods_pass():
+    output = StringIO()
+    with redirect_stdout(output), pytest.raises(SystemExit) as ex:
+        similar.Run(["--ignore-signatures", SIMILAR_CLS_B, SIMILAR_CLS_A])
+    assert ex.value.code == 0
+    assert (
+        output.getvalue().strip()
+        == """
+TOTAL lines=54 duplicates=0 percent=0.00
+""".strip()
+    )
+
+
 def test_ignore_signatures_empty_functions_fail():
     output = StringIO()
     with redirect_stdout(output), pytest.raises(SystemExit) as ex:
diff --git a/tests/input/similar_cls_a.py b/tests/input/similar_cls_a.py
new file mode 100644
index 000000000..9f4e149e2
--- /dev/null
+++ b/tests/input/similar_cls_a.py
@@ -0,0 +1,27 @@
+class A:
+    def parent_method(
+        self,
+        *,
+        a="",
+        b=None,
+        c=True,
+    ):
+        """Overridden method example."""
+
+        def _internal_func(
+            arg1: int = 1,
+            arg2: str = "2",
+            arg3: int = 3,
+            arg4: bool = True,
+        ):
+            pass
+
+    class InternalA:
+        def some_method_a(
+            self,
+            *,
+            a=None,
+            b=False,
+            c="",
+        ):
+            pass
diff --git a/tests/input/similar_cls_b.py b/tests/input/similar_cls_b.py
new file mode 100644
index 000000000..91df34a38
--- /dev/null
+++ b/tests/input/similar_cls_b.py
@@ -0,0 +1,27 @@
+class B:
+    def parent_method(
+        self,
+        *,
+        a="",
+        b=None,
+        c=True,
+    ):
+        """Overridden method example."""
+
+        def _internal_func(
+            arg1: int = 1,
+            arg2: str = "2",
+            arg3: int = 3,
+            arg4: bool = True,
+        ):
+            pass
+
+    class InternalB:
+        def some_method_b(
+            self,
+            *,
+            a=None,
+            b=False,
+            c="",
+        ):
+            pass