refactor: common function to serialise attributes and fix #1

Author: dimaqq

otlp_json/__init__.py

@@ -7,6 +7,8 @@
 if TYPE_CHECKING:
     from typing_extensions import TypeAlias
 
+    from opentelemetry.trace import Link
+    from opentelemetry._logs import LogRecord
     from opentelemetry.sdk.trace import ReadableSpan, Event
     from opentelemetry.sdk.resources import Resource
     from opentelemetry.sdk.util.instrumentation import InstrumentationScope
@@ -66,26 +68,27 @@ def encode_spans(spans: Sequence[ReadableSpan]) -> bytes:
 
 
 def _resource(resource: Resource):
-    rv = {"attributes": []}
-    for k, v in resource.attributes.items():
+    # TODO: add schema_url once that lands in opentelemetry-sdk
+    return _attributes(resource)
+
+
+def _attributes(
+    thing: Resource | InstrumentationScope | ReadableSpan | Event | Link | LogRecord,
+) -> dict[str, Any]:
+    rv = {"attributes": [], "dropped_attributes_count": 0}
+
+    assert thing.attributes is not None
+    for k, v in thing.attributes.items():
         try:
             rv["attributes"].append({"key": k, "value": _value(v)})
         except ValueError:
             pass
 
-    # NOTE: blocks that contain droppedAttributesCount:
-    # - Event
-    # - Link
-    # - InstrumentationScope
-    # - LogRecord (out of scope for this library)
-    # - Resource
-    rv["dropped_attributes_count"] = len(resource.attributes) - len(rv["attributes"])  # type: ignore
+    rv["dropped_attributes_count"] = len(thing.attributes) - len(rv["attributes"])  # type: ignore
 
-    if not rv["attributes"]:
-        del rv["attributes"]
-
-    if not rv["dropped_attributes_count"]:
-        del rv["dropped_attributes_count"]
+    for k in ("attributes", "dropped_attributes_count"):
+        if not rv[k]:
+            del rv[k]
 
     return rv
 
@@ -99,8 +102,9 @@ def _homogeneous_array(value: list[_LEAF_VALUE]) -> list[_LEAF_VALUE]:
 
 def _value(value: _VALUE) -> dict[str, Any]:
     # Attribute value can be a primitive type, excluging None...
-    # TODO: protobuf allows bytes, but I think OTLP doesn't.
-    # TODO: protobuf allows k:v pairs, but I think OTLP doesn't.
+    # protobuf allows bytes, but I think OTLP spec does not?
+    # protobuf allows k:v pairs, but I think OTLP doesn't.
+    # TODO: read up the spec and validate the allowed type range.
     for klass, (key, post) in _VALUE_TYPES.items():
         if isinstance(value, klass):
             return {key: post(value)}
@@ -109,7 +113,10 @@ def _value(value: _VALUE) -> dict[str, Any]:
 
 
 def _scope(scope: InstrumentationScope):
-    rv = {"name": scope.name}
+    rv = {
+        "name": scope.name,
+        **_attributes(scope),
+    }
     if scope.version:
         rv["version"] = scope.version
     return rv
@@ -123,29 +130,16 @@ def _span(span: ReadableSpan):
         "traceId": _trace_id(span.context.trace_id),
         "spanId": _span_id(span.context.span_id),
         "flags": 0x100 | ([0, 0x200][bool(span.parent and span.parent.is_remote)]),
-        "startTimeUnixNano": str(span.start_time),  # TODO: is it ever optional?
-        "endTimeUnixNano": str(span.end_time),  # -"-
+        "startTimeUnixNano": str(span.start_time),
+        "endTimeUnixNano": str(span.end_time),  # can this be unset?
         "status": _status(span.status),
-        "attributes": [],
+        **_attributes(span),
     }
 
     if span.parent:
         rv["parentSpanId"] = _span_id(span.parent.span_id)
 
-    for k, v in span.attributes.items():  # type: ignore
-        try:
-            rv["attributes"].append({"key": k, "value": _value(v)})
-        except ValueError:
-            pass
-
-    rv["dropped_attributes_count"] = len(span.attributes) - len(rv["attributes"])  # type: ignore
-
-    if not rv["attributes"]:
-        del rv["attributes"]
-
-    if not rv["dropped_attributes_count"]:
-        del rv["dropped_attributes_count"]
-
+    # TODO: is this field really nullable?
     if span.events:
         rv["events"] = [_event(e) for e in span.events]
 
@@ -165,29 +159,15 @@ def _span_id(span_id: int) -> str:
 
 
 def _status(status: Status) -> dict[str, Any]:
-    # FIXME
+    # FIXME: need an example of bad status
     return {}
 
 
 def _event(event: Event) -> dict[str, Any]:
     rv = {
         "name": event.name,
         "timeUnixNano": str(event.timestamp),
-        "attributes": [],
+        **_attributes(event),
     }
-
-    for k, v in event.attributes.items():  # type: ignore
-        try:
-            rv["attributes"].append({"key": k, "value": _value(v)})
-        except ValueError:
-            pass
-
-    rv["dropped_attributes_count"] = len(event.attributes) - len(rv["attributes"])  # type: ignore
-
-    if not rv["attributes"]:
-        del rv["attributes"]
-
-    if not rv["dropped_attributes_count"]:
-        del rv["dropped_attributes_count"]
-
+    # TODO: any optional attributes?
     return rv

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "otlp-json"
-version = "0.9.3"
+version = "0.9.4"
 description = "🐍Lightweight OTEL span to JSON converter, no dependencies, pure Python🐍"
 requires-python = ">=3.8"
 # https://github.com/astral-sh/uv/issues/4204