Fix NewRelicContextFormatter bug

Previously, there was a bug in NewRelicContextFormatter where "message" was added to the
default set of keys to exclude. This made the default key list (default keys + 1) in
length. Since the logic check was based on the length, rather than presence of certain
keys, anything that had one extra key than the default would not have that extra key
added to the ouput because the length would match the (default keys + 1) length.

The length check is a bit odd here as it leads to a bug in the implementation.
Instead, let's check for presence of keys which is more reflective of our intended
goal than checking the length.

newrelic/api/log.py

@@ -89,10 +89,11 @@ def log_record_to_dict(cls, record):
         output.update(get_linking_metadata())
 
         DEFAULT_LOG_RECORD_KEYS = cls.DEFAULT_LOG_RECORD_KEYS
-        if len(record.__dict__) > len(DEFAULT_LOG_RECORD_KEYS):
-            for key in record.__dict__:
-                if key not in DEFAULT_LOG_RECORD_KEYS:
-                    output["extra." + key] = getattr(record, key)
+        # If any keys are present in record that aren't in the default,
+        # add them to the output record.
+        keys_to_add = set(record.__dict__.keys()) - DEFAULT_LOG_RECORD_KEYS
+        for key in keys_to_add:
+            output["extra." + key] = getattr(record, key)
 
         if record.exc_info:
             output.update(format_exc_info(record.exc_info))

tests/agent_features/test_logs_in_context.py

@@ -61,6 +61,48 @@ def __str__(self):
     __repr__ = __str__
 
 
+def test_newrelic_logger_min_extra_keys_no_error(log_buffer):
+    extra = {
+        "string": "foo",
+    }
+    _logger.info("Hello %s", "World", extra=extra)
+
+    log_buffer.seek(0)
+    message = json.load(log_buffer)
+
+    timestamp = message.pop("timestamp")
+    thread_id = message.pop("thread.id")
+    process_id = message.pop("process.id")
+    filename = message.pop("file.name")
+    line_number = message.pop("line.number")
+
+    assert isinstance(timestamp, int)
+    assert isinstance(thread_id, int)
+    assert isinstance(process_id, int)
+    assert filename.endswith("/test_logs_in_context.py")
+    assert isinstance(line_number, int)
+
+    expected = {
+        "entity.name": "Python Agent Test (agent_features)",
+        "entity.type": "SERVICE",
+        "message": "Hello World",
+        "log.level": "INFO",
+        "logger.name": "test_logs_in_context",
+        "thread.name": "MainThread",
+        "process.name": "MainProcess",
+        "extra.string": "foo",
+    }
+    expected_extra_txn_keys = (
+        "entity.guid",
+        "hostname",
+    )
+
+    for k, v in expected.items():
+        assert message.pop(k) == v
+
+    assert set(message.keys()) == set(expected_extra_txn_keys)
+
+
 def test_newrelic_logger_no_error(log_buffer):
     extra = {
         "string": "foo",