Fixed invalid regex handling in filterwarnings (#13124)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Thomas Grainger <[email protected]>

changelog/13119.bugfix.rst

@@ -0,0 +1 @@
+Improved handling of invalid regex patterns for filter warnings by providing a clear error message.

src/_pytest/config/__init__.py

@@ -1953,6 +1953,13 @@ def parse_warning_filter(
             ) from None
     else:
         lineno = 0
+    try:
+        re.compile(message)
+        re.compile(module)
+    except re.error as e:
+        raise UsageError(
+            error_template.format(error=f"Invalid regex {e.pattern!r}: {e}")
+        ) from None
     return action, message, category, module, lineno
 
 

testing/test_warnings.py

@@ -511,6 +511,29 @@ def test_hidden_by_system(self, pytester: Pytester, monkeypatch) -> None:
         result = pytester.runpytest_subprocess()
         assert WARNINGS_SUMMARY_HEADER not in result.stdout.str()
 
+    def test_invalid_regex_in_filterwarning(self, pytester: Pytester) -> None:
+        self.create_file(pytester)
+        pytester.makeini(
+            """
+                [pytest]
+                filterwarnings =
+                    ignore::DeprecationWarning:*
+            """
+        )
+        result = pytester.runpytest_subprocess()
+        assert result.ret == pytest.ExitCode.USAGE_ERROR
+        result.stderr.fnmatch_lines(
+            [
+                "ERROR: while parsing the following warning configuration:",
+                "",
+                "  ignore::DeprecationWarning:[*]",
+                "",
+                "This error occurred:",
+                "",
+                "Invalid regex '[*]': nothing to repeat at position 0",
+            ]
+        )
+
 
 @pytest.mark.skip("not relevant until pytest 9.0")
 @pytest.mark.parametrize("change_default", [None, "ini", "cmdline"])