fix _encode_events assumes events.attributes.dropped exists

CHANGELOG.md

@@ -29,6 +29,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Version 1.25.0/0.46b0 (2024-05-30)
 
+- Fix _encode_events assumes events.attributes.dropped exists
+  ([#3965](https://github.com/open-telemetry/opentelemetry-python/pull/3965))
 - Fix class BoundedAttributes to have RLock rather than Lock
   ([#3859](https://github.com/open-telemetry/opentelemetry-python/pull/3859))
 - Remove thread lock by loading RuntimeContext explicitly.

exporter/opentelemetry-exporter-otlp-proto-common/src/opentelemetry/exporter/otlp/proto/common/_internal/trace_encoder/__init__.py

@@ -142,7 +142,7 @@ def _encode_events(
                 name=event.name,
                 time_unix_nano=event.timestamp,
                 attributes=_encode_attributes(event.attributes),
-                dropped_attributes_count=event.attributes.dropped,
+                dropped_attributes_count=event.dropped_attributes,
             )
             pb2_events.append(encoded_event)
     return pb2_events

exporter/opentelemetry-exporter-otlp-proto-grpc/tests/test_otlp_trace_exporter.py

@@ -149,7 +149,7 @@ def setUp(self):
         )
 
         type(event_mock).name = PropertyMock(return_value="a")
-
+        type(event_mock).dropped_attributes = PropertyMock(return_value=0)
         self.span = _Span(
             "a",
             context=Mock(

opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

@@ -337,6 +337,12 @@ def __init__(
     def attributes(self) -> types.Attributes:
         return self._attributes
 
+    @property
+    def dropped_attributes(self) -> int:
+        if isinstance(self._attributes, BoundedAttributes):
+            return self._attributes.dropped
+        return 0
+
 
 def _check_span_ended(func):
     def wrapper(self, *args, **kwargs):

opentelemetry-sdk/tests/trace/test_trace.py

@@ -27,6 +27,7 @@
 from unittest.mock import Mock, patch
 
 from opentelemetry import trace as trace_api
+from opentelemetry.attributes import BoundedAttributes
 from opentelemetry.context import Context
 from opentelemetry.sdk import resources, trace
 from opentelemetry.sdk.environment_variables import (
@@ -635,6 +636,15 @@ def test_events(self):
         span = trace.ReadableSpan("test", events=events)
         self.assertEqual(span.events, tuple(events))
 
+    def test_event_dropped_attributes(self):
+        event1 = trace.Event(
+            "foo1", BoundedAttributes(0, attributes={"bar1": "baz1"})
+        )
+        self.assertEqual(event1.dropped_attributes, 1)
+
+        event2 = trace.Event("foo2", {"bar2": "baz2"})
+        self.assertEqual(event2.dropped_attributes, 0)
+
 
 class DummyError(Exception):
     pass
@@ -1837,7 +1847,7 @@ def test_dropped_attributes(self):
         self.assertEqual(1, span.dropped_links)
         self.assertEqual(2, span.dropped_attributes)
         self.assertEqual(3, span.dropped_events)
-        self.assertEqual(2, span.events[0].attributes.dropped)
+        self.assertEqual(2, span.events[0].dropped_attributes)
         self.assertEqual(2, span.links[0].attributes.dropped)
 
     def _test_span_limits(