fix: stringify tuple dict keys in exception args

Author: Izaak Gough

src/firebase_functions/logger.py

@@ -148,14 +148,29 @@ def _coerce_json_safe(obj: _typing.Any):
     if isinstance(obj, str | int | float | bool | type(None)):
         return obj
     if isinstance(obj, dict):
-        return {_coerce_json_safe(key): _coerce_json_safe(value) for key, value in obj.items()}
+        return {
+            _coerce_json_safe_dict_key(key): _coerce_json_safe(value) for key, value in obj.items()
+        }
     if isinstance(obj, list):
         return [_coerce_json_safe(item) for item in obj]
     if isinstance(obj, tuple):
         return tuple(_coerce_json_safe(item) for item in obj)
     return _safe_repr(obj)
 
 
+def _coerce_json_safe_dict_key(obj: _typing.Any):
+    """
+    Converts dictionary keys into values accepted by JSON object encoding.
+    """
+
+    if isinstance(obj, str | int | float | bool | type(None)):
+        return obj
+    coerced = _coerce_json_safe(obj)
+    if isinstance(coerced, str | int | float | bool | type(None)):
+        return coerced
+    return _safe_repr(coerced)
+
+
 def _safe_repr(obj: _typing.Any) -> str:
     """
     Returns a repr without propagating repr errors.

tests/test_logger.py

@@ -179,6 +179,22 @@ def test_error_should_accept_exception_with_non_json_serializable_dict_key(
         assert log_output["error"]["type"] == "ValueError"
         assert log_output["error"]["args"] == [{repr(next(iter(payload.keys()))): "value"}]
 
+    def test_error_should_accept_exception_with_tuple_dict_key(
+        self, capsys: pytest.CaptureFixture[str]
+    ):
+        payload = {(1, "two"): "value"}
+        exception = ValueError(payload)
+
+        logger.error("failed", error=exception)
+
+        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"]["type"] == "ValueError"
+        assert log_output["error"]["args"] == [{"(1, 'two')": "value"}]
+
     def test_log_should_have_message(self, capsys: pytest.CaptureFixture[str]):
         logger.log("bar")
         raw_log_output = capsys.readouterr().out