Store namespaces respective to directories (#6789)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

7 files changed, 81 insertions, 1 deletions

diff --git a/.pyenchant_pylint_custom_dict.txt b/.pyenchant_pylint_custom_dict.txt
index b5d832d05..80918ac5a 100644
--- a/.pyenchant_pylint_custom_dict.txt
+++ b/.pyenchant_pylint_custom_dict.txt
@@ -21,6 +21,7 @@ async
 asynccontextmanager
 attr
 attrib
+backport
 BaseChecker
 basename
 behaviour
diff --git a/pylint/config/arguments_manager.py b/pylint/config/arguments_manager.py
index 301769e77..eda1a583d 100644
--- a/pylint/config/arguments_manager.py
+++ b/pylint/config/arguments_manager.py
@@ -42,7 +42,7 @@ from pylint.config.option_parser import OptionParser
 from pylint.config.options_provider_mixin import OptionsProviderMixIn
 from pylint.config.utils import _convert_option_to_argument, _parse_rich_type_value
 from pylint.constants import MAIN_CHECKER_NAME
-from pylint.typing import OptionDict
+from pylint.typing import DirectoryNamespaceDict, OptionDict
 
 if sys.version_info >= (3, 11):
     import tomllib
@@ -66,6 +66,14 @@ class _ArgumentsManager:
         self._config = argparse.Namespace()
         """Namespace for all options."""
 
+        self._base_config = self._config
+        """Fall back Namespace object created during initialization.
+
+        This is necessary for the per-directory configuration support. Whenever we
+        fail to match a file with a directory we fall back to the Namespace object
+        created during initialization.
+        """
+
         self._arg_parser = argparse.ArgumentParser(
             prog=prog,
             usage=usage or "%(prog)s [options]",
@@ -82,6 +90,9 @@ class _ArgumentsManager:
         self._option_dicts: dict[str, OptionDict] = {}
         """All option dictionaries that have been registered."""
 
+        self._directory_namespaces: DirectoryNamespaceDict = {}
+        """Mapping of directories and their respective namespace objects."""
+
         # TODO: 3.0: Remove deprecated attributes introduced to keep API
         # parity with optparse. Until '_maxlevel'
         with warnings.catch_warnings():
diff --git a/pylint/config/config_initialization.py b/pylint/config/config_initialization.py
index b5bd31234..7c67d08d6 100644
--- a/pylint/config/config_initialization.py
+++ b/pylint/config/config_initialization.py
@@ -106,6 +106,9 @@ def _config_initialization(
 
     linter._parse_error_mode()
 
+    # Link the base Namespace object on the current directory
+    linter._directory_namespaces[Path(".").resolve()] = (linter.config, {})
+
     # parsed_args_list should now only be a list of files/directories to lint.
     # All other options have been removed from the list.
     return parsed_args_list
diff --git a/pylint/lint/pylinter.py b/pylint/lint/pylinter.py
index 63eb84e10..625ab07f6 100644
--- a/pylint/lint/pylinter.py
+++ b/pylint/lint/pylinter.py
@@ -4,6 +4,7 @@
 
 from __future__ import annotations
 
+import argparse
 import collections
 import contextlib
 import functools
@@ -15,6 +16,7 @@ import warnings
 from collections import defaultdict
 from collections.abc import Callable, Iterable, Iterator, Sequence
 from io import TextIOWrapper
+from pathlib import Path
 from typing import Any
 
 import astroid
@@ -40,6 +42,7 @@ from pylint.lint.report_functions import (
     report_total_messages_stats,
 )
 from pylint.lint.utils import (
+    _is_relative_to,
     fix_import_path,
     get_fatal_error_message,
     prepare_crash_report,
@@ -49,6 +52,7 @@ from pylint.reporters.base_reporter import BaseReporter
 from pylint.reporters.text import TextReporter
 from pylint.reporters.ureports import nodes as report_nodes
 from pylint.typing import (
+    DirectoryNamespaceDict,
     FileItem,
     ManagedMessage,
     MessageDefinitionTuple,
@@ -791,6 +795,26 @@ class PyLinter(
         self.current_file = filepath or modname
         self.stats.init_single_module(modname or "")
 
+        # If there is an actual filepath we might need to update the config attribute
+        if filepath:
+            namespace = self._get_namespace_for_file(
+                Path(filepath), self._directory_namespaces
+            )
+            if namespace:
+                self.config = namespace or self._base_config
+
+    def _get_namespace_for_file(
+        self, filepath: Path, namespaces: DirectoryNamespaceDict
+    ) -> argparse.Namespace | None:
+        for directory in namespaces:
+            if _is_relative_to(filepath, directory):
+                namespace = self._get_namespace_for_file(
+                    filepath, namespaces[directory][1]
+                )
+                if namespace is None:
+                    return namespaces[directory][0]
+        return None
+
     @contextlib.contextmanager
     def _astroid_module_checker(
         self,
diff --git a/pylint/lint/utils.py b/pylint/lint/utils.py
index 30694c25c..ff2812e7e 100644
--- a/pylint/lint/utils.py
+++ b/pylint/lint/utils.py
@@ -99,3 +99,16 @@ def fix_import_path(args: Sequence[str]) -> Iterator[None]:
         yield
     finally:
         sys.path[:] = original
+
+
+def _is_relative_to(self: Path, *other: Path) -> bool:
+    """Checks if self is relative to other.
+
+    Backport of pathlib.Path.is_relative_to for Python <3.9
+    TODO: py39: Remove this backport and use stdlib function.
+    """
+    try:
+        self.relative_to(*other)
+        return True
+    except ValueError:
+        return False
diff --git a/pylint/typing.py b/pylint/typing.py
index f5650c1e7..7ceb33f91 100644
--- a/pylint/typing.py
+++ b/pylint/typing.py
@@ -6,7 +6,9 @@
 
 from __future__ import annotations
 
+import argparse
 import sys
+from pathlib import Path
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -127,3 +129,5 @@ MessageDefinitionTuple = Union[
     Tuple[str, str, str],
     Tuple[str, str, str, ExtraMessageOptions],
 ]
+# Mypy doesn't support recursive types (yet), see https://github.com/python/mypy/issues/731
+DirectoryNamespaceDict = Dict[Path, Tuple[argparse.Namespace, "DirectoryNamespaceDict"]]  # type: ignore[misc]
diff --git a/tests/config/test_per_directory_config.py b/tests/config/test_per_directory_config.py
new file mode 100644
index 000000000..9bc0ef9bc
--- /dev/null
+++ b/tests/config/test_per_directory_config.py
@@ -0,0 +1,24 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
+
+
+from py._path.local import LocalPath  # type: ignore[import]
+
+from pylint.lint import Run
+
+
+def test_fall_back_on_base_config(tmpdir: LocalPath) -> None:
+    """Test that we correctly fall back on the base config."""
+    # A file under the current dir should fall back to the highest level
+    # For pylint this is ./pylintrc
+    test_file = tmpdir / "test.py"
+    runner = Run([__name__], exit=False)
+    assert id(runner.linter.config) == id(runner.linter._base_config)
+
+    # When the file is a directory that does not have any of its parents in
+    # linter._directory_namespaces it should default to the base config
+    with open(test_file, "w", encoding="utf-8") as f:
+        f.write("1")
+    Run([str(test_file)], exit=False)
+    assert id(runner.linter.config) == id(runner.linter._base_config)