Fix JSON span event encoding in v1 payloads.

dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/TraceMapperV1.java

@@ -1,6 +1,7 @@
 package datadog.trace.common.writer.ddagent;
 
 import static datadog.communication.http.OkHttpUtils.msgpackRequestBodyOf;
+import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonMap;
 
@@ -11,6 +12,7 @@
 import datadog.communication.serialization.Writable;
 import datadog.communication.serialization.msgpack.MsgPackWriter;
 import datadog.environment.JavaVirtualMachine;
+import datadog.json.JsonReader;
 import datadog.trace.api.Config;
 import datadog.trace.api.DDTags;
 import datadog.trace.api.DDTraceId;
@@ -203,12 +205,12 @@ private void encodeSpanLinks(
 
   private void encodeSpanEvents(Writable writable, int fieldId, Object eventsObject) {
     writable.writeInt(fieldId);
-    if (!(eventsObject instanceof List) || ((List<?>) eventsObject).isEmpty()) {
+    List<?> events = parseSpanEvents(eventsObject);
+    if (events.isEmpty()) {
       writable.startArray(0);
       return;
     }
 
-    List<?> events = (List<?>) eventsObject;
     int encodableCount = 0;
     for (Object event : events) {
       if (isEncodableSpanEvent(event)) {
@@ -237,6 +239,23 @@ private void encodeSpanEvents(Writable writable, int fieldId, Object eventsObjec
     }
   }
 
+  private List<?> parseSpanEvents(Object eventsObject) {
+    if (eventsObject instanceof List) {
+      return (List<?>) eventsObject;
+    }
+    if (eventsObject instanceof CharSequence) {
+      try (JsonReader reader = new JsonReader(eventsObject.toString())) {
+        Object events = reader.nextValue();
+        if (events instanceof List) {
+          return (List<?>) events;
+        }
+      } catch (IOException e) {
+        log.debug("Failed to parse span events from JSON", e);
+      }
+    }
+    return emptyList();
+  }
+
   private boolean isEncodableSpanEvent(Object event) {
     if (!(event instanceof Map)) {
       return false;

dd-trace-core/src/test/java/datadog/trace/core/DDSpanSerializationTest.java

@@ -1,5 +1,6 @@
 package datadog.trace.core;
 
+import static datadog.trace.api.DDTags.SPAN_EVENTS;
 import static datadog.trace.api.DDTags.SPAN_LINKS;
 import static datadog.trace.api.TracePropagationStyle.DATADOG;
 import static datadog.trace.api.config.GeneralConfig.EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED;
@@ -400,6 +401,52 @@ void serializeTraceWithSpanLinksAsStructuredLinksOnlyV1() throws Exception {
     tracer.close();
   }
 
+  @Test
+  void serializeTraceWithJsonSpanEventsV1() throws Exception {
+    CoreTracer tracer = tracerBuilder().writer(new ListWriter()).build();
+    DDSpanContext context = createSpanContext(tracer, Collections.emptyMap(), null, true, true, 1);
+    context.setTag(
+        SPAN_EVENTS,
+        "[{\"time_unix_nano\":1234567890,\"name\":\"event.one\","
+            + "\"attributes\":{\"str\":\"value\",\"int\":42,\"double\":12.5,"
+            + "\"bool\":true,\"arr\":[\"x\",7,2.5,false]}},"
+            + "{\"time_unix_nano\":1234567891,\"name\":\"event.two\"}]");
+    DDSpan span = DDSpan.create("test", 0, context, null);
+
+    V1PayloadReader.V1Span payload = V1PayloadReader.readFirstSpan(serializeV1Payload(span));
+
+    assertFalse(payload.getAttributes().containsKey(SPAN_EVENTS));
+    assertEquals(2, payload.getEvents().size());
+    V1PayloadReader.V1SpanEvent firstEvent = payload.getEvents().get(0);
+    assertEquals(1234567890L, firstEvent.getTimeUnixNano());
+    assertEquals("event.one", firstEvent.getName());
+    assertEquals("value", firstEvent.getAttributes().get("str"));
+    assertEquals(42L, firstEvent.getAttributes().get("int"));
+    assertEquals(12.5d, firstEvent.getAttributes().get("double"));
+    assertEquals(true, firstEvent.getAttributes().get("bool"));
+    assertEquals(Arrays.asList("x", 7L, 2.5d, false), firstEvent.getAttributes().get("arr"));
+
+    V1PayloadReader.V1SpanEvent secondEvent = payload.getEvents().get(1);
+    assertEquals(1234567891L, secondEvent.getTimeUnixNano());
+    assertEquals("event.two", secondEvent.getName());
+    assertEquals(Collections.emptyMap(), secondEvent.getAttributes());
+    tracer.close();
+  }
+
+  @Test
+  void serializeTraceWithMalformedJsonSpanEventsAsEmptyV1() throws Exception {
+    CoreTracer tracer = tracerBuilder().writer(new ListWriter()).build();
+    DDSpanContext context = createSpanContext(tracer, Collections.emptyMap(), null, true, true, 1);
+    context.setTag(SPAN_EVENTS, "[{");
+    DDSpan span = DDSpan.create("test", 0, context, null);
+
+    V1PayloadReader.V1Span payload = V1PayloadReader.readFirstSpan(serializeV1Payload(span));
+
+    assertFalse(payload.getAttributes().containsKey(SPAN_EVENTS));
+    assertEquals(Collections.emptyList(), payload.getEvents());
+    tracer.close();
+  }
+
   @TableTest({
     "protocol | rootFirst",
     "v0.4     | true     ",