fix: preserve active traceback for custom error payloads

Author: Izaak Gough

src/firebase_functions/logger.py

@@ -270,11 +270,12 @@ def exception(*args, **kwargs) -> None:
     """
     Logs an error message and includes the active stack trace.
     """
+    raw_error = kwargs.get("error")
     entry = _entry_from_args(LogSeverity.ERROR, *args, **kwargs)
     exc_type, exc_value, exc_traceback = _sys.exc_info()
     if exc_type is not None and exc_value is not None and exc_traceback is not None:
-        error = entry.get("error")
-        if not isinstance(error, dict) or "stack_trace" not in error:
+        uses_active_error_traceback = raw_error is exc_value or raw_error is exc_type
+        if not uses_active_error_traceback:
             entry["stack_trace"] = "".join(
                 _traceback.format_exception(exc_type, exc_value, exc_traceback)
             )

tests/test_logger.py

@@ -266,6 +266,23 @@ def test_exception_should_not_duplicate_stack_trace_for_exception_type_error(
         assert "stack_trace" in log_output["error"]
         assert "TypeError: boom" in log_output["error"]["stack_trace"]
 
+    def test_exception_should_include_active_stack_trace_for_error_dict(
+        self, capsys: pytest.CaptureFixture[str]
+    ):
+        try:
+            raise ValueError("boom")
+        except ValueError:
+            logger.exception("failed", error={"stack_trace": "custom traceback"})
+
+        raw_log_output = capsys.readouterr().err
+        log_output = json.loads(raw_log_output)
+
+        assert log_output["severity"] == "ERROR"
+        assert log_output["message"] == "failed"
+        assert log_output["error"] == {"stack_trace": "custom traceback"}
+        assert "stack_trace" in log_output
+        assert "ValueError: boom" in log_output["stack_trace"]
+
     def test_remove_circular_references(self, capsys: pytest.CaptureFixture[str]):
         # Create an object with a circular reference.
         circ = {"b": "foo"}