Prevent remaster from updating fallback versioned expected outputs

pylint/testutils/functional/test_file.py

@@ -103,6 +103,15 @@ def module(self) -> str:
 
     @property
     def expected_output(self) -> str:
+        output, _ = self._resolve_expected_output()
+        return output
+
+    @property
+    def expected_output_is_fallback(self) -> bool:
+        _, is_fallback = self._resolve_expected_output()
+        return is_fallback
+
+    def _resolve_expected_output(self) -> tuple[str, bool]:
         files = [
             p.stem
             for p in Path(self._directory).glob(f"{split(self.base)[-1]}.[0-9]*.txt")
@@ -115,8 +124,11 @@ def expected_output(self) -> str:
         for opt in sorted(output_options, reverse=True):
             if _CURRENT_VERSION >= opt:
                 str_opt = "".join([str(s) for s in opt])
-                return join(self._directory, f"{self.base}.{str_opt}.txt")
-        return join(self._directory, self.base + ".txt")
+                return (
+                    join(self._directory, f"{self.base}.{str_opt}.txt"),
+                    _CURRENT_VERSION != opt,
+                )
+        return join(self._directory, self.base + ".txt"), False
 
     @property
     def source(self) -> str:

tests/test_functional.py

@@ -66,6 +66,9 @@ def test_functional(
     else:
         actual_output = lint_test.check_messages()
 
-    golden_master.check(
-        lint_test.serialize_output(actual_output), test_file.expected_output
-    )
+    serialized_output = lint_test.serialize_output(actual_output)
+    if test_file.expected_output_is_fallback:
+        expected = Path(test_file.expected_output).read_text(encoding="utf-8")
+        assert serialized_output.rstrip() == expected.rstrip()
+    else:
+        golden_master.check(serialized_output, test_file.expected_output)

tests/testutils/test_functional_testutils.py

@@ -127,6 +127,55 @@ def test_expected_output_file_matching(files: list[str], output_file_name: str)
             assert test_file.expected_output == f".{os.path.sep}{output_file_name}"
 
 
+@pytest.mark.parametrize(
+    ["files", "output_file_name", "is_fallback"],
+    [
+        ([], "file.txt", False),
+        (["file.txt"], "file.txt", False),
+        (["file.315.txt"], "file.txt", False),  # don't match 3.15
+        (["file.42.txt"], "file.txt", False),  # don't match 4.2
+        (["file.32.txt", "file.txt"], "file.32.txt", True),
+        (["file.313.txt", "file.txt"], "file.313.txt", True),
+        (["file.314.txt", "file.txt"], "file.314.txt", False),
+        (
+            [
+                "file.310.txt",
+                "file.313.txt",
+                "file.312.txt",
+                "file.314.txt",
+                "file.txt",
+            ],
+            "file.314.txt",
+            False,
+        ),
+        (
+            ["file.310.txt", "file.313.txt", "file.312.txt", "file.txt"],
+            "file.313.txt",
+            True,
+        ),
+        # don't match other test file names accidentally
+        ([".file.313.txt"], "file.txt", False),
+        (["file_other.313.txt"], "file.txt", False),
+        (["other_file.313.txt"], "file.txt", False),
+    ],
+)
+def test_expected_output_fallback_detection(
+    files: list[str], output_file_name: str, is_fallback: bool
+) -> None:
+    """Test output file fallback detection. Pin current Python version to 3.13."""
+    with tempdir():
+        for file in files:
+            with open(file, "w", encoding="utf-8"):
+                ...
+        test_file = FunctionalTestFile(".", "file.py")
+        with patch(
+            "pylint.testutils.functional.test_file._CURRENT_VERSION",
+            new=(3, 14),
+        ):
+            assert test_file.expected_output == f".{os.path.sep}{output_file_name}"
+            assert test_file.expected_output_is_fallback is is_fallback
+
+
 def test_minimal_messages_config_enabled(pytest_config: MagicMock) -> None:
     """Test that all messages not targeted in the functional test are disabled
     when running with --minimal-messages-config.