Fix NPE on null span type tag, and add regression test

mtoffl01 · mtoffl01 · commit 96954d7d9500 · 2026-04-29T16:23:40.000-04:00
diff --git a/dd-trace-core/src/main/java/datadog/trace/core/otlp/trace/OtlpTraceProto.java b/dd-trace-core/src/main/java/datadog/trace/core/otlp/trace/OtlpTraceProto.java
@@ -138,7 +138,9 @@ public static byte[] recordSpanMessage(
     }
     writeSpanTag(buf, RESOURCE_NAME, span.getResourceName());
     writeSpanTag(buf, OPERATION_NAME, span.getOperationName());
-    writeSpanTag(buf, SPAN_TYPE, span.getSpanType());
+    if (span.getSpanType() != null) {
+      writeSpanTag(buf, SPAN_TYPE, span.getSpanType());
+    }
 
     span.processTagsAndBaggage(metaWriter);
 
@@ -222,17 +224,11 @@ private static void writeSpanTag(StreamingBuffer buf, TagMap.EntryReader tagEntr
 
   private static void writeSpanTag(
       StreamingBuffer buf, UTF8BytesString key, UTF8BytesString value) {
-    if (value == null) {
-      return;
-    }
     writeTag(buf, 9, LEN_WIRE_TYPE);
     writeAttribute(buf, key, value);
   }
 
   private static void writeSpanTag(StreamingBuffer buf, UTF8BytesString key, CharSequence value) {
-    if (value == null) {
-      return;
-    }
     writeTag(buf, 9, LEN_WIRE_TYPE);
     if (value instanceof UTF8BytesString) {
       writeAttribute(buf, key, (UTF8BytesString) value);
diff --git a/dd-trace-core/src/test/java/datadog/trace/core/otlp/trace/OtlpTraceProtoTest.java b/dd-trace-core/src/test/java/datadog/trace/core/otlp/trace/OtlpTraceProtoTest.java
@@ -443,6 +443,11 @@ static Stream<Arguments> cases() {
         Arguments.of(
             "minimal span — default UNSPECIFIED kind",
             asList(span("GET /api/users", "servlet.request", "web"))),
+
+        // ── null span type — regression: must not NPE, span.type attribute omitted ─
+        Arguments.of(
+            "null span type — span.type attribute omitted, no NPE",
+            asList(span("GET /api/users", "servlet.request", null))),
         Arguments.of("internal span kind", asList(kindSpan("GET /api/users", SPAN_KIND_INTERNAL))),
         Arguments.of("server span kind", asList(kindSpan("GET /api/users", SPAN_KIND_SERVER))),
         Arguments.of("client span kind", asList(kindSpan("redis.get", SPAN_KIND_CLIENT))),
@@ -1029,8 +1034,14 @@ private static void verifySpan(CodedInputStream sp, DDSpan span, SpanSpec spec,
     assertTrue(
         attrKeys.contains("operation.name"),
         "attributes must include 'operation.name' [" + caseName + "]");
-    assertTrue(
-        attrKeys.contains("span.type"), "attributes must include 'span.type' [" + caseName + "]");
+    if (spec.spanType != null) {
+      assertTrue(
+          attrKeys.contains("span.type"), "attributes must include 'span.type' [" + caseName + "]");
+    } else {
+      assertFalse(
+          attrKeys.contains("span.type"),
+          "attributes must omit 'span.type' when null [" + caseName + "]");
+    }
 
     // service.name attribute is written only when the span's service differs from the default
     if (spec.serviceName != null) {
