Makes functional tests auto-update works even if the current output is wrong

doc/whatsnew/2/2.15/index.rst

@@ -61,3 +61,9 @@ Internal changes
 * ``pylint.testutils.primer`` is now a private API.
 
   Refs #6905
+
+* Fixed an issue where it was impossible to update functional tests output when the existing
+  output was impossible to parse. Instead of raising an error we raise a warning message and
+  let the functional test fail with a default value.
+
+  Refs #6891

pylint/testutils/output_line.py

@@ -33,44 +33,6 @@ class MessageTest(NamedTuple):
     """
 
 
-class MalformedOutputLineException(Exception):
-    def __init__(
-        self,
-        row: Sequence[str] | str,
-        exception: Exception,
-    ) -> None:
-        example = "msg-symbolic-name:42:27:MyClass.my_function:The message"
-        other_example = "msg-symbolic-name:7:42::The message"
-        expected = [
-            "symbol",
-            "line",
-            "column",
-            "end_line",
-            "end_column",
-            "MyClass.myFunction, (or '')",
-            "Message",
-            "confidence",
-        ]
-        reconstructed_row = ""
-        i = 0
-        try:
-            for i, column in enumerate(row):
-                reconstructed_row += f"\t{expected[i]}='{column}' ?\n"
-            for missing in expected[i + 1 :]:
-                reconstructed_row += f"\t{missing}= Nothing provided !\n"
-        except IndexError:
-            pass
-        raw = ":".join(row)
-        msg = f"""\
-{exception}
-
-Expected '{example}' or '{other_example}' but we got '{raw}':
-{reconstructed_row}
-
-Try updating it with: 'python tests/test_functional.py {UPDATE_OPTION}'"""
-        super().__init__(msg)
-
-
 class OutputLine(NamedTuple):
     symbol: str
     lineno: int
@@ -127,6 +89,7 @@ def from_csv(
         """
         if isinstance(row, str):
             row = row.split(",")
+        # noinspection PyBroadException
         try:
             column = cls._get_column(row[2])
             if len(row) == 5:
@@ -170,8 +133,14 @@ def from_csv(
                     row[7],
                 )
             raise IndexError
-        except Exception as e:
-            raise MalformedOutputLineException(row, e) from e
+        except Exception:  # pylint: disable=broad-except
+            warnings.warn(
+                "Expected 'msg-symbolic-name:42:27:MyClass.my_function:The message:"
+                f"CONFIDENCE' but we got '{':'.join(row)}'. Try updating the expected"
+                f" output with:\npython tests/test_functional.py {UPDATE_OPTION}",
+                UserWarning,
+            )
+            return cls("", 0, 0, None, None, "", "", "")
 
     def to_csv(self) -> tuple[str, str, str, str, str, str, str, str]:
         """Convert an OutputLine to a tuple of string to be written by a

tests/testutils/test_output_line.py

@@ -13,7 +13,7 @@
 from pylint.constants import PY38_PLUS
 from pylint.interfaces import HIGH, INFERENCE, Confidence
 from pylint.message import Message
-from pylint.testutils.output_line import MalformedOutputLineException, OutputLine
+from pylint.testutils.output_line import OutputLine
 from pylint.typing import MessageLocationTuple
 
 
@@ -127,20 +127,20 @@ def test_output_line_to_csv(confidence: Confidence, message: Callable) -> None:
 def test_output_line_from_csv_error() -> None:
     """Test that errors are correctly raised for incorrect OutputLine's."""
     # Test a csv-string which does not have a number for line and column
-    with pytest.raises(
-        MalformedOutputLineException,
+    with pytest.warns(
+        UserWarning,
         match="msg-symbolic-name:42:27:MyClass.my_function:The message",
     ):
         OutputLine.from_csv("'missing-docstring', 'line', 'column', 'obj', 'msg'", True)
     # Test a tuple which does not have a number for line and column
-    with pytest.raises(
-        MalformedOutputLineException, match="symbol='missing-docstring' ?"
+    with pytest.warns(
+        UserWarning, match="we got 'missing-docstring:line:column:obj:msg'"
     ):
         csv = ("missing-docstring", "line", "column", "obj", "msg")
         OutputLine.from_csv(csv, True)
     # Test a csv-string that is too long
-    with pytest.raises(
-        MalformedOutputLineException,
+    with pytest.warns(
+        UserWarning,
         match="msg-symbolic-name:42:27:MyClass.my_function:The message",
     ):
         OutputLine.from_csv(