opentelemetry-sdk: handle none timestamp in LogRecord serialization

Author: xrmx

opentelemetry-sdk/src/opentelemetry/sdk/_logs/_internal/__init__.py

@@ -306,7 +306,9 @@ def to_json(self, indent: int | None = 4) -> str:
                     dict(self.attributes) if bool(self.attributes) else None
                 ),
                 "dropped_attributes": self.dropped_attributes,
-                "timestamp": ns_to_iso_str(self.timestamp),
+                "timestamp": ns_to_iso_str(self.timestamp)
+                if self.timestamp is not None
+                else None,
                 "observed_timestamp": ns_to_iso_str(self.observed_timestamp),
                 "trace_id": (
                     f"0x{format_trace_id(self.trace_id)}"

opentelemetry-sdk/tests/logs/test_log_record.py

@@ -62,6 +62,16 @@ def test_log_record_to_json_serializes_severity_number_as_int(self):
         decoded = json.loads(actual.to_json())
         self.assertEqual(SeverityNumber.WARN.value, decoded["severity_number"])
 
+    def test_log_record_to_json_serializes_null_severity_number(self):
+        actual = LogRecord(
+            observed_timestamp=0,
+            body="a log line",
+            resource=Resource({"service.name": "foo"}),
+        )
+
+        decoded = json.loads(actual.to_json())
+        self.assertEqual(None, decoded["timestamp"])
+
     def test_log_record_bounded_attributes(self):
         attr = {"key": "value"}