Refactor ``find_default_config_files`` (#6067)

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

5 files changed, 211 insertions, 69 deletions

diff --git a/pylint/config/find_default_config_files.py b/pylint/config/find_default_config_files.py
index 70e867ad6..71ba222b3 100644
--- a/pylint/config/find_default_config_files.py
+++ b/pylint/config/find_default_config_files.py
@@ -14,6 +14,9 @@ if sys.version_info >= (3, 11):
 else:
     import tomli as tomllib
 
+RC_NAMES = (Path("pylintrc"), Path(".pylintrc"))
+CONFIG_NAMES = RC_NAMES + (Path("pyproject.toml"), Path("setup.cfg"))
+
 
 def _toml_has_config(path: Union[Path, str]) -> bool:
     with open(path, mode="rb") as toml_handle:
@@ -34,43 +37,41 @@ def _cfg_has_config(path: Union[Path, str]) -> bool:
     return any(section.startswith("pylint.") for section in parser.sections())
 
 
-def find_default_config_files() -> Iterator[str]:
+def find_default_config_files() -> Iterator[Path]:
     """Find all possible config files."""
-    rc_names = ("pylintrc", ".pylintrc")
-    config_names = rc_names + ("pyproject.toml", "setup.cfg")
-    for config_name in config_names:
-        if os.path.isfile(config_name):
-            if config_name.endswith(".toml") and not _toml_has_config(config_name):
+    for config_name in CONFIG_NAMES:
+        if config_name.is_file():
+            if config_name.suffix == ".toml" and not _toml_has_config(config_name):
                 continue
-            if config_name.endswith(".cfg") and not _cfg_has_config(config_name):
+            if config_name.suffix == ".cfg" and not _cfg_has_config(config_name):
                 continue
 
-            yield os.path.abspath(config_name)
+            yield config_name.resolve()
 
-    if os.path.isfile("__init__.py"):
-        curdir = os.path.abspath(os.getcwd())
-        while os.path.isfile(os.path.join(curdir, "__init__.py")):
-            curdir = os.path.abspath(os.path.join(curdir, ".."))
-            for rc_name in rc_names:
-                rc_path = os.path.join(curdir, rc_name)
-                if os.path.isfile(rc_path):
-                    yield rc_path
+    if Path("__init__.py").is_file():
+        curdir = Path(os.getcwd()).resolve()
+        while (curdir / "__init__.py").is_file():
+            curdir = curdir.parent
+            for rc_name in RC_NAMES:
+                rc_path = curdir / rc_name
+                if rc_path.is_file():
+                    yield rc_path.resolve()
 
-    if "PYLINTRC" in os.environ and os.path.exists(os.environ["PYLINTRC"]):
-        if os.path.isfile(os.environ["PYLINTRC"]):
-            yield os.environ["PYLINTRC"]
+    if "PYLINTRC" in os.environ and Path(os.environ["PYLINTRC"]).exists():
+        if Path(os.environ["PYLINTRC"]).is_file():
+            yield Path(os.environ["PYLINTRC"]).resolve()
     else:
-        user_home = os.path.expanduser("~")
-        if user_home not in ("~", "/root"):
-            home_rc = os.path.join(user_home, ".pylintrc")
-            if os.path.isfile(home_rc):
-                yield home_rc
-            home_rc = os.path.join(user_home, ".config", "pylintrc")
-            if os.path.isfile(home_rc):
-                yield home_rc
+        user_home = Path.home()
+        if str(user_home) not in ("~", "/root"):
+            home_rc = user_home / ".pylintrc"
+            if home_rc.is_file():
+                yield home_rc.resolve()
+            home_rc = user_home / ".config" / "pylintrc"
+            if home_rc.is_file():
+                yield home_rc.resolve()
 
     if os.path.isfile("/etc/pylintrc"):
-        yield "/etc/pylintrc"
+        yield Path("/etc/pylintrc").resolve()
 
 
 def find_pylintrc() -> Optional[str]:
@@ -84,6 +85,6 @@ def find_pylintrc() -> Optional[str]:
         DeprecationWarning,
     )
     for config_file in find_default_config_files():
-        if config_file.endswith("pylintrc"):
-            return config_file
+        if str(config_file).endswith("pylintrc"):
+            return str(config_file)
     return None
diff --git a/pylint/testutils/__init__.py b/pylint/testutils/__init__.py
index 0b55fc8e9..e9b8de1de 100644
--- a/pylint/testutils/__init__.py
+++ b/pylint/testutils/__init__.py
@@ -18,6 +18,7 @@ __all__ = [
     "UPDATE_FILE",
     "UPDATE_OPTION",
     "UnittestLinter",
+    "create_files",
 ]
 
 from pylint.testutils.checker_test_case import CheckerTestCase
@@ -31,3 +32,4 @@ from pylint.testutils.output_line import MessageTest
 from pylint.testutils.reporter_for_tests import GenericTestReporter, MinimalTestReporter
 from pylint.testutils.tokenize_str import _tokenize_str
 from pylint.testutils.unittest_linter import UnittestLinter
+from pylint.testutils.utils import create_files
diff --git a/pylint/testutils/utils.py b/pylint/testutils/utils.py
new file mode 100644
index 000000000..a6a588194
--- /dev/null
+++ b/pylint/testutils/utils.py
@@ -0,0 +1,44 @@
+# 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
+
+import os
+from typing import List
+
+
+def create_files(paths: List[str], chroot: str = ".") -> None:
+    """Creates directories and files found in <path>.
+
+    :param list paths: list of relative paths to files or directories
+    :param str chroot: the root directory in which paths will be created
+
+    >>> from os.path import isdir, isfile
+    >>> isdir('/tmp/a')
+    False
+    >>> create_files(['a/b/foo.py', 'a/b/c/', 'a/b/c/d/e.py'], '/tmp')
+    >>> isdir('/tmp/a')
+    True
+    >>> isdir('/tmp/a/b/c')
+    True
+    >>> isfile('/tmp/a/b/c/d/e.py')
+    True
+    >>> isfile('/tmp/a/b/foo.py')
+    True
+    """
+    dirs, files = set(), set()
+    for path in paths:
+        path = os.path.join(chroot, path)
+        filename = os.path.basename(path)
+        # path is a directory path
+        if filename == "":
+            dirs.add(path)
+        # path is a filename path
+        else:
+            dirs.add(os.path.dirname(path))
+            files.add(path)
+    for dirpath in dirs:
+        if not os.path.isdir(dirpath):
+            os.makedirs(dirpath)
+    for filepath in files:
+        with open(filepath, "w", encoding="utf-8"):
+            pass
diff --git a/tests/config/test_find_default_config_files.py b/tests/config/test_find_default_config_files.py
index 04392781b..ca1461bad 100644
--- a/tests/config/test_find_default_config_files.py
+++ b/tests/config/test_find_default_config_files.py
@@ -1,13 +1,145 @@
 # 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
+
+import contextlib
+import importlib
+import os
+import shutil
+import sys
+import tempfile
 from pathlib import Path
+from typing import Iterator
 
 import pytest
 
+from pylint import config, testutils
 from pylint.config.find_default_config_files import _cfg_has_config, _toml_has_config
 
 
+@pytest.fixture
+def pop_pylintrc() -> None:
+    """Remove the PYLINTRC environment variable"""
+    os.environ.pop("PYLINTRC", None)
+
+
+if os.name == "java":
+    if os.name == "nt":
+        HOME = "USERPROFILE"
+    else:
+        HOME = "HOME"
+elif sys.platform == "win32":
+    HOME = "USERPROFILE"
+else:
+    HOME = "HOME"
+
+
+@contextlib.contextmanager
+def fake_home() -> Iterator[None]:
+    """Fake a home directory."""
+    folder = tempfile.mkdtemp("fake-home")
+    old_home = os.environ.get(HOME)
+    try:
+        os.environ[HOME] = folder
+        yield
+    finally:
+        os.environ.pop("PYLINTRC", "")
+        if old_home is None:
+            del os.environ[HOME]
+        else:
+            os.environ[HOME] = old_home
+        shutil.rmtree(folder, ignore_errors=True)
+
+
+@contextlib.contextmanager
+def tempdir() -> Iterator[str]:
+    """Create a temp directory and change the current location to it.
+
+    This is supposed to be used with a *with* statement.
+    """
+    tmp = tempfile.mkdtemp()
+
+    # Get real path of tempfile, otherwise test fail on mac os x
+    current_dir = os.getcwd()
+    os.chdir(tmp)
+    abs_tmp = os.path.abspath(".")
+
+    try:
+        yield abs_tmp
+    finally:
+        os.chdir(current_dir)
+        shutil.rmtree(abs_tmp)
+
+
+@pytest.mark.usefixtures("pop_pylintrc")
+def test_pylintrc() -> None:
+    """Test that the environment variable is checked for existence."""
+    with fake_home():
+        current_dir = os.getcwd()
+        os.chdir(os.path.dirname(os.path.abspath(sys.executable)))
+        try:
+            assert not list(config.find_default_config_files())
+            os.environ["PYLINTRC"] = os.path.join(tempfile.gettempdir(), ".pylintrc")
+            assert not list(config.find_default_config_files())
+            os.environ["PYLINTRC"] = "."
+            assert not list(config.find_default_config_files())
+        finally:
+            os.chdir(current_dir)
+            importlib.reload(config)
+
+
+@pytest.mark.usefixtures("pop_pylintrc")
+def test_pylintrc_parentdir() -> None:
+    """Test that the first pylintrc we find is the first parent directory."""
+    with tempdir() as chroot:
+        chroot_path = Path(chroot)
+        testutils.create_files(
+            [
+                "a/pylintrc",
+                "a/b/__init__.py",
+                "a/b/pylintrc",
+                "a/b/c/__init__.py",
+                "a/b/c/d/__init__.py",
+                "a/b/c/d/e/.pylintrc",
+            ]
+        )
+
+        with fake_home():
+            assert not list(config.find_default_config_files())
+
+        results = {
+            "a": chroot_path / "a" / "pylintrc",
+            "a/b": chroot_path / "a" / "b" / "pylintrc",
+            "a/b/c": chroot_path / "a" / "b" / "pylintrc",
+            "a/b/c/d": chroot_path / "a" / "b" / "pylintrc",
+            "a/b/c/d/e": chroot_path / "a" / "b" / "c" / "d" / "e" / ".pylintrc",
+        }
+        for basedir, expected in results.items():
+            os.chdir(chroot_path / basedir)
+            assert next(config.find_default_config_files()) == expected
+
+
+@pytest.mark.usefixtures("pop_pylintrc")
+def test_pylintrc_parentdir_no_package() -> None:
+    """Test that we don't find a pylintrc in sub-packages."""
+    with tempdir() as chroot:
+        with fake_home():
+            chroot_path = Path(chroot)
+            testutils.create_files(
+                ["a/pylintrc", "a/b/pylintrc", "a/b/c/d/__init__.py"]
+            )
+            assert config.find_pylintrc() is None
+            results = {
+                "a": chroot_path / "a" / "pylintrc",
+                "a/b": chroot_path / "a" / "b" / "pylintrc",
+                "a/b/c": None,
+                "a/b/c/d": None,
+            }
+            for basedir, expected in results.items():
+                os.chdir(chroot_path / basedir)
+                assert next(config.find_default_config_files(), None) == expected
+
+
 @pytest.mark.parametrize(
     "content,expected",
     [
diff --git a/tests/lint/unittest_lint.py b/tests/lint/unittest_lint.py
index 90faa1c2f..d973cf892 100644
--- a/tests/lint/unittest_lint.py
+++ b/tests/lint/unittest_lint.py
@@ -12,7 +12,7 @@ from contextlib import contextmanager
 from importlib import reload
 from io import StringIO
 from os import chdir, getcwd
-from os.path import abspath, basename, dirname, isdir, join, sep
+from os.path import abspath, dirname, join, sep
 from shutil import rmtree
 from typing import Iterable, Iterator, List, Optional, Tuple
 
@@ -32,6 +32,7 @@ from pylint.exceptions import InvalidMessageError
 from pylint.lint import ArgumentPreprocessingError, PyLinter, Run, preprocess_options
 from pylint.message import Message
 from pylint.reporters import text
+from pylint.testutils import create_files
 from pylint.typing import MessageLocationTuple
 from pylint.utils import FileState, print_full_documentation, tokenize_module
 
@@ -95,44 +96,6 @@ def tempdir() -> Iterator[str]:
         rmtree(abs_tmp)
 
 
-def create_files(paths: List[str], chroot: str = ".") -> None:
-    """Creates directories and files found in <path>.
-
-    :param list paths: list of relative paths to files or directories
-    :param str chroot: the root directory in which paths will be created
-
-    >>> from os.path import isdir, isfile
-    >>> isdir('/tmp/a')
-    False
-    >>> create_files(['a/b/foo.py', 'a/b/c/', 'a/b/c/d/e.py'], '/tmp')
-    >>> isdir('/tmp/a')
-    True
-    >>> isdir('/tmp/a/b/c')
-    True
-    >>> isfile('/tmp/a/b/c/d/e.py')
-    True
-    >>> isfile('/tmp/a/b/foo.py')
-    True
-    """
-    dirs, files = set(), set()
-    for path in paths:
-        path = join(chroot, path)
-        filename = basename(path)
-        # path is a directory path
-        if filename == "":
-            dirs.add(path)
-        # path is a filename path
-        else:
-            dirs.add(dirname(path))
-            files.add(path)
-    for dirpath in dirs:
-        if not isdir(dirpath):
-            os.makedirs(dirpath)
-    for filepath in files:
-        with open(filepath, "w", encoding="utf-8"):
-            pass
-
-
 @pytest.fixture
 def fake_path() -> Iterator[Iterable[str]]:
     orig = list(sys.path)