feat: Configure comma separated values on the style file

README.rst

@@ -110,3 +110,16 @@ To enforce that certain files should not exist in the project, you can add them
 
 Multiple files can be configured as above.
 The ``message`` is optional.
+
+Comma separated values (setup.cfg)
+----------------------------------
+
+On ``setup.cfg``, some keys are lists of multiple values separated by commas, like ``flake8.ignore``.
+
+On the style file, it's possible to indicate which key/value pairs should be treated as multiple values instead of an exact string.
+Multiple keys can be added.
+
+.. code-block:: ini
+
+    ["setup.cfg"]
+    comma_separated_values = ["flake8.ignore", "isort.some_key", "another_section.another_key"]

flake8_nitpick/__init__.py

@@ -3,7 +3,7 @@
 import logging
 from configparser import ConfigParser
 from io import StringIO
-from typing import Optional, Tuple, Type, Any, Dict, Generator, List, MutableMapping, Union
+from typing import Optional, Tuple, Type, Any, Dict, Generator, List, MutableMapping, Union, Set
 
 import os
 import dictdiffer
@@ -333,13 +333,16 @@ class SetupCfgChecker(BaseChecker):
     file_name = "setup.cfg"
     error_base_number = 320
 
-    COMMA_SEPARATED_KEYS = {"flake8.ignore"}
+    COMMA_SEPARATED_VALUES = "comma_separated_values"
+    comma_separated_values: Set[str]
 
     def check_rules(self) -> YieldFlake8Error:
         """Check missing sections and missing key/value pairs in setup.cfg."""
         if not self.file_path.exists():
             return
 
+        self.comma_separated_values = set(self.file_toml.pop(self.COMMA_SEPARATED_VALUES, []))
+
         setup_cfg = ConfigParser()
         setup_cfg.read_file(self.file_path.open())
 
@@ -369,7 +372,7 @@ def check_rules(self) -> YieldFlake8Error:
     def compare_different_keys(self, section, key, raw_expected: Any, raw_actual: Any) -> YieldFlake8Error:
         """Compare different keys, with special treatment when they are lists or numeric."""
         combined = f"{section}.{key}"
-        if combined in self.COMMA_SEPARATED_KEYS:
+        if combined in self.comma_separated_values:
             # The values might contain spaces
             actual_set = {s.strip() for s in raw_actual.split(",")}
             expected_set = {s.strip() for s in raw_expected.split(",")}

nitpick-style.toml

@@ -45,6 +45,9 @@ ipdb = "*"
 pylint = "*"
 mypy = "*"
 
+["setup.cfg"]
+comma_separated_values = ["flake8.ignore"]
+
 ["setup.cfg".flake8]
 # http://www.pydocstyle.org/en/2.1.1/error_codes.html
 # Ignoring W503: https://github.com/ambv/black#line-breaks--binary-operators

tests/helpers.py

@@ -1,11 +1,19 @@
 """Test helpers."""
 import os
 from pathlib import Path
+from pprint import pprint
 from typing import List, Set
 
 from _pytest.fixtures import FixtureRequest
 
-from flake8_nitpick import NITPICK_STYLE_TOML, Flake8Error, NitpickChecker, PyProjectTomlChecker, SetupCfgChecker
+from flake8_nitpick import (
+    ERROR_PREFIX,
+    NITPICK_STYLE_TOML,
+    Flake8Error,
+    NitpickChecker,
+    PyProjectTomlChecker,
+    SetupCfgChecker,
+)
 from tests.conftest import TEMP_ROOT_PATH
 
 
@@ -48,9 +56,9 @@ def lint(self, file_index: int = 0) -> "ProjectMock":
         self.errors = set()
         for flake8_error in self.original_errors:
             line, col, message, class_ = flake8_error
-            assert line
+            assert line == 1
             assert col == 0
-            assert message
+            assert message.startswith(ERROR_PREFIX)
             assert class_ is NitpickChecker
             self.errors.add(message)
         return self
@@ -74,3 +82,13 @@ def setup_cfg(self, file_contents: str) -> "ProjectMock":
     def pyproject_toml(self, file_contents: str):
         """Save pyproject.toml."""
         return self.save_file(PyProjectTomlChecker.file_name, file_contents)
+
+    def assert_errors_contain(self, error: str) -> None:
+        """Assert the error is in the error set."""
+        if error in self.errors:
+            return
+
+        print(f"Expected error:\n{error}")
+        print("\nAll errors:")
+        pprint(self.errors, width=150)
+        assert False

tests/test_nitpick.py

@@ -19,27 +19,29 @@ def test_no_main_python_file_root_dir(request):
     }
 
 
-def test_comma_separated_keys(request):
-    """Comma separated keys on setup.cfg."""
+def test_comma_separated_keys_on_style_file(request):
+    """Comma separated keys on the style file."""
     project = (
         ProjectMock(request)
         .style(
             """
-["setup.cfg".flake8]
-ignore = "salt,ham,eggs"
+["setup.cfg"]
+comma_separated_values = ["food.eat"]
+
+["setup.cfg".food]
+eat = "salt,ham,eggs"
 """
         )
         .setup_cfg(
             """
-[flake8]
-ignore = spam,eggs,cheese
+[food]
+eat = spam,eggs,cheese
 """
         )
         .lint()
     )
-    assert (
+    project.assert_errors_contain(
         """NIP322 File: setup.cfg: Missing values in key
-[flake8]
-ignore = ham,salt"""
-        in project.errors
+[food]
+eat = ham,salt"""
     )