Patch sys.path on a per-file basis

doc/whatsnew/fragments/7339.other

@@ -0,0 +1,3 @@
+Pylint now tries to patch ``sys.path`` on a per file basis instead of per run.
+
+Closes #7339

pylint/lint/expand_modules.py

@@ -11,36 +11,20 @@
 
 from astroid import modutils
 
+from pylint.lint.utils import get_python_path
 from pylint.typing import ErrorDescriptionDict, ModuleDescriptionDict
 
 
 def _modpath_from_file(filename: str, is_namespace: bool, path: list[str]) -> list[str]:
     def _is_package_cb(inner_path: str, parts: list[str]) -> bool:
+        # with fix_import_path((inner_path,)):
         return modutils.check_modpath_has_init(inner_path, parts) or is_namespace
 
     return modutils.modpath_from_file_with_callback(
         filename, path=path, is_package_cb=_is_package_cb
     )
 
 
-def get_python_path(filepath: str) -> str:
-    """TODO This get the python path with the (bad) assumption that there is always
-    an __init__.py.
-
-    This is not true since python 3.3 and is causing problem.
-    """
-    dirname = os.path.realpath(os.path.expanduser(filepath))
-    if not os.path.isdir(dirname):
-        dirname = os.path.dirname(dirname)
-    while True:
-        if not os.path.exists(os.path.join(dirname, "__init__.py")):
-            return dirname
-        old_dirname = dirname
-        dirname = os.path.dirname(dirname)
-        if old_dirname == dirname:
-            return os.getcwd()
-
-
 def _is_in_ignore_list_re(element: str, ignore_list_re: list[Pattern[str]]) -> bool:
     """Determines if the element is matched in a regex ignore-list."""
     return any(file_pattern.match(element) for file_pattern in ignore_list_re)

pylint/lint/pylinter.py

@@ -658,6 +658,8 @@ def check(self, files_or_modules: Sequence[str] | str) -> None:
             return
 
         # 3) Get all FileItems
+        # TODO: 2.16: See if this sys.path patching can be removed as we already
+        # do this in _expand_modules as well
         with fix_import_path(files_or_modules):
             if self.config.from_stdin:
                 fileitems = iter(
@@ -670,12 +672,11 @@ def check(self, files_or_modules: Sequence[str] | str) -> None:
 
         # The contextmanager also opens all checkers and sets up the PyLinter class
         with self._astroid_module_checker() as check_astroid_module:
-            with fix_import_path(files_or_modules):
-                # 4) Get the AST for each FileItem
-                ast_per_fileitem = self._get_asts(fileitems, data)
+            # 4) Get the AST for each FileItem
+            ast_per_fileitem = self._get_asts(fileitems, data)
 
-                # 5) Lint each ast
-                self._lint_files(ast_per_fileitem, check_astroid_module)
+            # 5) Lint each ast
+            self._lint_files(ast_per_fileitem, check_astroid_module)
 
     def _get_asts(
         self, fileitems: Iterator[FileItem], data: str | None
@@ -1026,9 +1027,10 @@ def check_astroid_module(
         """
         before_check_statements = walker.nbstatements
 
-        retval = self._check_astroid_module(
-            ast_node, walker, rawcheckers, tokencheckers
-        )
+        with fix_import_path((ast_node.file or "",)):
+            retval = self._check_astroid_module(
+                ast_node, walker, rawcheckers, tokencheckers
+            )
 
         # TODO: 3.0: Remove unnecessary assertion
         assert self.current_name

pylint/lint/utils.py

@@ -5,14 +5,32 @@
 from __future__ import annotations
 
 import contextlib
+import os
 import sys
 import traceback
 from collections.abc import Iterator, Sequence
 from datetime import datetime
 from pathlib import Path
 
 from pylint.config import PYLINT_HOME
-from pylint.lint.expand_modules import get_python_path
+
+
+def get_python_path(filepath: str) -> str:
+    """TODO This get the python path with the (bad) assumption that there is always
+    an __init__.py.
+
+    This is not true since python 3.3 and is causing problem.
+    """
+    dirname = os.path.realpath(os.path.expanduser(filepath))
+    if not os.path.isdir(dirname):
+        dirname = os.path.dirname(dirname)
+    while True:
+        if not os.path.exists(os.path.join(dirname, "__init__.py")):
+            return dirname
+        old_dirname = dirname
+        dirname = os.path.dirname(dirname)
+        if old_dirname == dirname:
+            return os.getcwd()
 
 
 def prepare_crash_report(ex: Exception, filepath: str, crash_file_path: str) -> Path:

tests/lint/unittest_lint.py

@@ -12,6 +12,7 @@
 import re
 import sys
 import tempfile
+import textwrap
 from collections.abc import Iterable, Iterator
 from contextlib import contextmanager
 from importlib import reload
@@ -986,3 +987,32 @@ def test_lint_namespace_package_under_dir_on_path(initialized_linter: PyLinter)
         with fix_import_path([tmpdir]):
             linter.check(["namespace_on_path"])
     assert linter.file_state.base_name == "namespace_on_path"
+
+
+def test_sys_path_patching_for_namespace_package(initialized_linter: PyLinter) -> None:
+    """Test that a normal package in the arguments doesn't pollute sys.path.
+
+    Originally reported in https://github.com/PyCQA/pylint/issues/7339.
+    If pylint is run over a file within a namespace package which
+    shares the name with a normal package that 1) is stored in another directory
+    and 2) is being linted at the same time previously there would be a clash of names
+    due to the addition of the normal package to sys.path.
+    This was fixed by only patching sys.path on a per-file basis.
+    """
+    linter = initialized_linter
+    with tempdir() as tmpdir:
+        create_files(["ns1/m1.py", "ns1/m2.py", "ns2/ns1/__init__.py"])
+        with open(os.path.join(tmpdir, "ns1/m1.py"), "w", encoding="utf-8") as f:
+            f.write(
+                textwrap.dedent(
+                    """
+            '''Test file'''
+            import ns1.m2
+            print(ns1.m2)
+            """
+                )
+            )
+        os.chdir(tmpdir)
+        with fix_import_path([tmpdir]):
+            linter.check(["ns1/m1.py", "ns2/ns1/__init__.py"])
+    assert not linter.reporter.messages

tests/test_functional.py

@@ -14,6 +14,7 @@
 from _pytest.recwarn import WarningsRecorder
 
 from pylint import testutils
+from pylint.lint.utils import fix_import_path
 from pylint.testutils import UPDATE_FILE, UPDATE_OPTION
 from pylint.testutils.functional import (
     FunctionalTestFile,
@@ -50,7 +51,11 @@ def test_functional(
     else:
         lint_test = testutils.LintModuleTest(test_file, pytestconfig)
     lint_test.setUp()
-    lint_test.runTest()
+    # Pytest changes 'sys.path' depending on the files you're running over.
+    # To fix this, we simply patch sys.path like we do in a normal run, but
+    # as if we're running against the test file.
+    with fix_import_path((test_file.source,)):
+        lint_test.runTest()
     if recwarn.list:
         if (
             test_file.base in TEST_WITH_EXPECTED_DEPRECATION

tests/test_self.py

@@ -267,7 +267,7 @@ def test_wrong_import_position_when_others_disabled(self) -> None:
         module2 = join(HERE, "regrtest_data", "wrong_import_position.py")
         expected_output = textwrap.dedent(
             f"""
-        ************* Module wrong_import_position
+        ************* Module regrtest_data.wrong_import_position
         {module2}:11:0: C0413: Import "import os" should be placed at the top of the module (wrong-import-position)
         """
         )
@@ -325,7 +325,7 @@ def test_json_report_when_file_has_syntax_error(self) -> None:
             "line": 1,
             "type": "error",
             "symbol": "syntax-error",
-            "module": "syntax_error",
+            "module": "regrtest_data.syntax_error",
         }
         message = output[0]
         for key, value in expected.items():
@@ -368,7 +368,7 @@ def test_json_report_does_not_escape_quotes(self) -> None:
         assert isinstance(output[0], dict)
         expected = {
             "symbol": "unused-variable",
-            "module": "unused_variable",
+            "module": "regrtest_data.unused_variable",
             "column": 4,
             "message": "Unused variable 'variable'",
             "message-id": "W0612",
@@ -389,7 +389,7 @@ def test_error_mode_shows_no_score(self) -> None:
         module = join(HERE, "regrtest_data", "application_crash.py")
         expected_output = textwrap.dedent(
             f"""
-        ************* Module application_crash
+        ************* Module regrtest_data.application_crash
         {module}:1:6: E0602: Undefined variable 'something_undefined' (undefined-variable)
         """
         )
@@ -446,7 +446,7 @@ def test_pylintrc_comments_in_values(self) -> None:
         config_path = join(HERE, "regrtest_data", "comments_pylintrc")
         expected = textwrap.dedent(
             f"""
-        ************* Module test_pylintrc_comments
+        ************* Module regrtest_data.test_pylintrc_comments
         {path}:2:0: W0311: Bad indentation. Found 1 spaces, expected 4 (bad-indentation)
         {path}:1:0: C0114: Missing module docstring (missing-module-docstring)
         {path}:1:0: C0116: Missing function or method docstring (missing-function-docstring)