Add a warning in functional test update for bad python versions

Author: Pierre-Sassoulas

pylint/testutils/functional/find_functional_tests.py

@@ -22,7 +22,7 @@ def get_functional_test_files_from_directory(
 
         assert (
             len(filenames) <= REASONABLY_DISPLAYABLE_VERTICALLY
-        ), f"{dirpath} contain too much functional tests files."
+        ), f"{dirpath} contains too many functional tests files."
 
         for filename in filenames:
             if filename != "__init__.py" and filename.endswith(".py"):

pylint/testutils/functional/lint_module_output_update.py

@@ -3,7 +3,12 @@
 
 import csv
 import os
+from typing import Optional
 
+from _pytest.config import Config
+
+from pylint.constants import PY38_PLUS
+from pylint.testutils.functional.test_file import FunctionalTestFile
 from pylint.testutils.lint_module_test import LintModuleTest
 
 
@@ -16,6 +21,17 @@ class TestDialect(csv.excel):
 
     csv.register_dialect("test", TestDialect)
 
+    def __init__(
+        self, test_file: FunctionalTestFile, config: Optional[Config] = None
+    ) -> None:
+        if not PY38_PLUS:
+            raise RuntimeError(
+                "You need at least python 3.8 for the functional test updater to work. "
+                "This is because python 3.8 includes a new AST parser, which amongst others "
+                "returns the end line and end column of most nodes."
+            )
+        super().__init__(test_file, config)
+
     def _check_output_text(self, _, expected_output, actual_output):
         if not expected_output and not actual_output:
             if os.path.exists(self._test_file.expected_output):

pylint/testutils/functional_test_file.py

@@ -16,7 +16,7 @@
 )
 
 warnings.warn(
-    "'pylint.testutils.functional_test_file' will be accessible by"
-    " the 'pylint.testutils.functional' API in pylint 3.0",
+    "'pylint.testutils.functional_test_file' will be accessible from"
+    " the 'pylint.testutils.functional' namespace in pylint 3.0.",
     DeprecationWarning,
 )

tests/testutils/test_lint_module_output_update.py

@@ -7,6 +7,7 @@
 
 import pytest
 
+from pylint.constants import PY38_PLUS
 from pylint.testutils import FunctionalTestFile
 from pylint.testutils.functional import LintModuleOutputUpdate
 
@@ -26,6 +27,15 @@ def inner(base: str) -> Tuple[Path, Path, LintModuleOutputUpdate]:
     return inner
 
 
+@pytest.mark.skipif(PY38_PLUS, reason="Requires python 3.7 or lower")
+def test_not_py38(tmp_path: Path) -> None:
+    with pytest.raises(RuntimeError, match="new, better AST in python 3.8"):
+        LintModuleOutputUpdate(
+            test_file=FunctionalTestFile(str(tmp_path), str(tmp_path / "filename.py"))
+        )
+
+
+@pytest.mark.skipif(not PY38_PLUS, reason="Requires python 3.8 or superior")
 def test_lint_module_output_update_fail_before(
     lint_module_fixture: Callable[[str], Tuple[Path, Path, LintModuleOutputUpdate]]
 ) -> None:
@@ -38,6 +48,7 @@ def test_lint_module_output_update_fail_before(
     assert not expected_output_file.exists()
 
 
+@pytest.mark.skipif(not PY38_PLUS, reason="Requires python 3.8 or superior")
 def test_lint_module_output_update_effective(
     lint_module_fixture: Callable[[str], Tuple[Path, Path, LintModuleOutputUpdate]]
 ) -> None:
@@ -52,6 +63,7 @@ def test_lint_module_output_update_effective(
     )
 
 
+@pytest.mark.skipif(not PY38_PLUS, reason="Requires python 3.8 or superior")
 def test_lint_module_output_update_remove_useless_txt(
     lint_module_fixture: Callable[[str], Tuple[Path, Path, LintModuleOutputUpdate]]
 ) -> None: