Suppress OSError in config file discovery (pylint-dev#7423)

doc/whatsnew/fragments/7169.bugfix

@@ -0,0 +1,3 @@
+Don't crash on ``OSError`` in config file discovery.
+
+Closes #7169

pylint/config/find_default_config_files.py

@@ -39,17 +39,26 @@ def _cfg_has_config(path: Path | str) -> bool:
     return any(section.startswith("pylint.") for section in parser.sections())
 
 
-def find_default_config_files() -> Iterator[Path]:
-    """Find all possible config files."""
+def _yield_default_files() -> Iterator[Path]:
+    """Iterate over the default config file names and see if they exist."""
     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.suffix == ".cfg" and not _cfg_has_config(config_name):
-                continue
+        try:
+            if config_name.is_file():
+                if config_name.suffix == ".toml" and not _toml_has_config(config_name):
+                    continue
+                if config_name.suffix == ".cfg" and not _cfg_has_config(config_name):
+                    continue
+
+                yield config_name.resolve()
+        except OSError:
+            pass
+
 
-            yield config_name.resolve()
+def _find_project_config() -> Iterator[Path]:
+    """Traverse up the directory tree to find a config file.
 
+    Stop if no '__init__' is found and thus we are no longer in a package.
+    """
     if Path("__init__.py").is_file():
         curdir = Path(os.getcwd()).resolve()
         while (curdir / "__init__.py").is_file():
@@ -59,6 +68,9 @@ def find_default_config_files() -> Iterator[Path]:
                 if rc_path.is_file():
                     yield rc_path.resolve()
 
+
+def _find_config_in_home_or_environment() -> Iterator[Path]:
+    """Find a config file in the specified environment var or the home directory."""
     if "PYLINTRC" in os.environ and Path(os.environ["PYLINTRC"]).exists():
         if Path(os.environ["PYLINTRC"]).is_file():
             yield Path(os.environ["PYLINTRC"]).resolve()
@@ -68,16 +80,36 @@ def find_default_config_files() -> Iterator[Path]:
         except RuntimeError:
             # If the home directory does not exist a RuntimeError will be raised
             user_home = None
+
         if user_home is not None and 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 Path("/etc/pylintrc").resolve()
+
+def find_default_config_files() -> Iterator[Path]:
+    """Find all possible config files."""
+    yield from _yield_default_files()
+
+    try:
+        yield from _find_project_config()
+    except OSError:
+        pass
+
+    try:
+        yield from _find_config_in_home_or_environment()
+    except OSError:
+        pass
+
+    try:
+        if os.path.isfile("/etc/pylintrc"):
+            yield Path("/etc/pylintrc").resolve()
+    except OSError:
+        pass
 
 
 def find_pylintrc() -> str | None:

tests/config/test_find_default_config_files.py

@@ -253,3 +253,12 @@ def test_non_existent_home() -> None:
         assert not list(config.find_default_config_files())
 
         os.chdir(current_dir)
+
+
+def test_permission_error() -> None:
+    """Test that we handle PermissionError correctly in find_default_config_files.
+
+    Reported in https://github.com/PyCQA/pylint/issues/7169.
+    """
+    with mock.patch("pathlib.Path.is_file", side_effect=PermissionError):
+        list(config.find_default_config_files())