Do not check private functions for args, returns or raises

README.md

@@ -6,6 +6,12 @@ assumes that the docstrings already pass `pydocstyle` checks. This
 [blog post](https://jdkandersson.com/2023/01/07/writing-great-docstrings-in-python/)
 discusses how to write great docstrings and the motivation for this linter!
 
+Following [PEP-8](https://peps.python.org/pep-0008/#documentation-strings),
+Docstrings are not necessary for non-public methods, but you should have a
+comment that describes what the method does. The definition taken for private
+functions/methods is that they start with a single underscore (`_`).
+
+
 ## Getting Started
 
 ```shell
@@ -1672,3 +1678,6 @@ Section information is extracted using the following algorithm:
 - Check that argument, exceptions and attributes have non-empty description.
 - Check that arguments, exceptions and attributes have meaningful descriptions.
 - Check other other PEP257 conventions
+- The definition for private functions is a function starting with a single `_`. This could be extended to functions starting with `__`
+  and not ending in `__`, that is functions with [name mangling](https://docs.python.org/3/tutorial/classes.html#private-variables)
+  but not [magic methods](https://docs.python.org/3/reference/datamodel.html#special-lookup).

flake8_docstrings_complete/__init__.py

@@ -53,6 +53,7 @@
     f"{MORE_INFO_BASE}{MULT_YIELDS_SECTIONS_IN_DOCSTR_CODE.lower()}"
 )
 
+PRIVATE_FUNCTION_PATTERN = r"_[^_].*"
 TEST_FILENAME_PATTERN_ARG_NAME = "--docstrings-complete-test-filename-pattern"
 TEST_FILENAME_PATTERN_DEFAULT = r"test_.*\.py"
 TEST_FUNCTION_PATTERN_ARG_NAME = "--docstrings-complete-test-function-pattern"
@@ -77,22 +78,26 @@ def _cli_arg_name_to_attr(cli_arg_name: str) -> str:
 
 
 def _check_returns(
-    docstr_info: docstring.Docstring, docstr_node: ast.Constant, return_nodes: Iterable[ast.Return]
+    docstr_info: docstring.Docstring,
+    docstr_node: ast.Constant,
+    return_nodes: Iterable[ast.Return],
+    is_private: bool,
 ) -> Iterator[types_.Problem]:
     """Check function/ method returns section.
 
     Args:
         docstr_info: Information about the docstring.
         docstr_node: The docstring node.
         return_nodes: The return nodes of the function.
+        is_private: If the function for the docstring is private.
 
     Yields:
         All the problems with the returns section.
     """
     return_nodes_with_value = list(node for node in return_nodes if node.value is not None)
 
     # Check for return statements with value and no returns section in docstring
-    if return_nodes_with_value and not docstr_info.returns_sections:
+    if return_nodes_with_value and not docstr_info.returns_sections and not is_private:
         yield from (
             types_.Problem(node.lineno, node.col_offset, RETURNS_SECTION_NOT_IN_DOCSTR_MSG)
             for node in return_nodes_with_value
@@ -117,21 +122,23 @@ def _check_yields(
     docstr_info: docstring.Docstring,
     docstr_node: ast.Constant,
     yield_nodes: Iterable[ast.Yield | ast.YieldFrom],
+    is_private: bool,
 ) -> Iterator[types_.Problem]:
     """Check function/ method yields section.
 
     Args:
         docstr_info: Information about the docstring.
         docstr_node: The docstring node.
         yield_nodes: The yield and yield from nodes of the function.
+        is_private: If the function for the docstring is private.
 
     Yields:
         All the problems with the yields section.
     """
     yield_nodes_with_value = list(node for node in yield_nodes if node.value is not None)
 
     # Check for yield statements with value and no yields section in docstring
-    if yield_nodes_with_value and not docstr_info.yields_sections:
+    if yield_nodes_with_value and not docstr_info.yields_sections and not is_private:
         yield from (
             types_.Problem(node.lineno, node.col_offset, YIELDS_SECTION_NOT_IN_DOCSTR_MSG)
             for node in yield_nodes_with_value
@@ -372,11 +379,17 @@ def visit_any_function(self, node: ast.FunctionDef | ast.AsyncFunctionDef) -> No
                 and isinstance(node.body[0].value, ast.Constant)
                 and isinstance(node.body[0].value.value, str)
             ):
+                is_private = bool(re.match(PRIVATE_FUNCTION_PATTERN, node.name))
                 # Check args
                 docstr_info = docstring.parse(value=node.body[0].value.value)
                 docstr_node = node.body[0].value
                 self.problems.extend(
-                    args.check(docstr_info=docstr_info, docstr_node=docstr_node, args=node.args)
+                    args.check(
+                        docstr_info=docstr_info,
+                        docstr_node=docstr_node,
+                        args=node.args,
+                        is_private=is_private,
+                    )
                 )
 
                 # Check returns
@@ -387,6 +400,7 @@ def visit_any_function(self, node: ast.FunctionDef | ast.AsyncFunctionDef) -> No
                         docstr_info=docstr_info,
                         docstr_node=docstr_node,
                         return_nodes=visitor_within_function.return_nodes,
+                        is_private=is_private,
                     )
                 )
 
@@ -396,6 +410,7 @@ def visit_any_function(self, node: ast.FunctionDef | ast.AsyncFunctionDef) -> No
                         docstr_info=docstr_info,
                         docstr_node=docstr_node,
                         yield_nodes=visitor_within_function.yield_nodes,
+                        is_private=is_private,
                     )
                 )
 
@@ -405,6 +420,7 @@ def visit_any_function(self, node: ast.FunctionDef | ast.AsyncFunctionDef) -> No
                         docstr_info=docstr_info,
                         docstr_node=docstr_node,
                         raise_nodes=visitor_within_function.raise_nodes,
+                        is_private=is_private,
                     )
                 )
 

flake8_docstrings_complete/args.py

@@ -67,7 +67,10 @@ def _iter_args(args: ast.arguments) -> Iterator[ast.arg]:
 
 
 def check(
-    docstr_info: docstring.Docstring, docstr_node: ast.Constant, args: ast.arguments
+    docstr_info: docstring.Docstring,
+    docstr_node: ast.Constant,
+    args: ast.arguments,
+    is_private: bool,
 ) -> Iterator[types_.Problem]:
     """Check that all function/ method arguments are described in the docstring.
 
@@ -80,6 +83,7 @@ def check(
         docstr_info: Information about the docstring.
         docstr_node: The docstring node.
         args: The arguments of the function.
+        is_private: If the function for the docstring is private.
 
     Yields:
         All the problems with the arguments.
@@ -88,7 +92,7 @@ def check(
     all_used_args = list(arg for arg in all_args if not arg.arg.startswith(UNUSED_ARGS_PREFIX))
 
     # Check that args section is in docstring if function/ method has used arguments
-    if all_used_args and docstr_info.args is None:
+    if all_used_args and docstr_info.args is None and not is_private:
         yield types_.Problem(
             docstr_node.lineno, docstr_node.col_offset, ARGS_SECTION_NOT_IN_DOCSTR_MSG
         )

flake8_docstrings_complete/raises.py

@@ -85,7 +85,10 @@ def _get_exc_node(node: ast.Raise) -> types_.Node | None:
 
 
 def check(
-    docstr_info: docstring.Docstring, docstr_node: ast.Constant, raise_nodes: Iterable[ast.Raise]
+    docstr_info: docstring.Docstring,
+    docstr_node: ast.Constant,
+    raise_nodes: Iterable[ast.Raise],
+    is_private: bool,
 ) -> Iterator[types_.Problem]:
     """Check that all raised exceptions arguments are described in the docstring.
 
@@ -97,6 +100,7 @@ def check(
         docstr_info: Information about the docstring.
         docstr_node: The docstring node.
         raise_nodes: The raise nodes.
+        is_private: If the function for the docstring is private.
 
     Yields:
         All the problems with exceptions.
@@ -106,7 +110,7 @@ def check(
     all_raise_no_value = all(exc is None for exc in all_excs)
 
     # Check that raises section is in docstring if function/ method raises exceptions
-    if all_excs and docstr_info.raises is None:
+    if all_excs and docstr_info.raises is None and not is_private:
         yield types_.Problem(
             docstr_node.lineno, docstr_node.col_offset, RAISES_SECTION_NOT_IN_DOCSTR_MSG
         )

tests/unit/test___init__.py

@@ -31,6 +31,14 @@ def function_1():
         ),
         pytest.param(
             """
+def _function_1():
+    return
+""",
+            (f"2:0 {DOCSTR_MISSING_MSG}",),
+            id="private function docstring missing return",
+        ),
+        pytest.param(
+            """
 @overload
 def function_1():
     ...
@@ -250,6 +258,15 @@ def function_1():
         ),
         pytest.param(
             '''
+def _function_1():
+    """Docstring."""
+    yield 1
+''',
+            (),
+            id="private function single yield value yields not in docstring",
+        ),
+        pytest.param(
+            '''
 def function_1():
     """Docstring."""
     yield from tuple()

tests/unit/test___init__args.py

@@ -474,6 +474,14 @@ def function_1(_arg_1):
         ),
         pytest.param(
             '''
+def _function_1(arg_1):
+    """Docstring 1."""
+''',
+            (),
+            id="prive function single arg docstring no arg",
+        ),
+        pytest.param(
+            '''
 def function_1(_arg_1):
     """Docstring 1."""
 ''',

tests/unit/test___init__raises.py

@@ -31,6 +31,15 @@ def function_1():
         ),
         pytest.param(
             '''
+def _function_1():
+    """Docstring 1."""
+    raise Exc1
+''',
+            (),
+            id="private function raises single exc docstring no raises section",
+        ),
+        pytest.param(
+            '''
 def function_1():
     """Docstring 1."""
     raise Exc1