feat(logger): readable log_dict seq

Ensure that the initial key seq is: timestamp,level,location,message

Closes #138

Author: Michael Brewer

aws_lambda_powertools/logging/formatter.py

@@ -53,6 +53,7 @@ def __init__(self, **kwargs):
             "timestamp": "%(asctime)s",
             "level": "%(levelname)s",
             "location": "%(funcName)s:%(lineno)d",
+            "message": "",
         }
         self.format_dict.update(kwargs)
 

tests/functional/test_aws_lambda_logging.py

@@ -116,3 +116,16 @@ class Unserializable:
     # THEN json_default should not be in the log message and the custom unserializable handler should be used
     assert log_dict["message"]["x"] == "<non-serializable: Unserializable>"
     assert "json_default" not in log_dict
+
+
+def test_log_dict_key_seq(stdout):
+    # GIVEN any logger configuration
+    logger = Logger(level="INFO", stream=stdout, another="xxx")
+
+    # WHEN logging a message
+    logger.info("Message")
+
+    log_dict: dict = json.loads(stdout.getvalue())
+
+    # THEN the key sequence should be `timestamp,level,location,message`
+    assert ",".join(list(log_dict.keys())[:4]) == "timestamp,level,location,message"