only serialize empty strings for attributes (StringAnyValue)

Author: breedx-splk

exporters/common/src/main/java/io/opentelemetry/exporter/internal/marshal/Serializer.java

@@ -254,11 +254,19 @@ public void serializeRepeatedString(ProtoFieldInfo field, byte[][] utf8Bytes) th
    */
   public void serializeStringWithContext(
       ProtoFieldInfo field, @Nullable String string, MarshalerContext context) throws IOException {
+    serializeStringWithContext(field, string, context, /* allowEmpty= */ false);
+  }
+
+  public void serializeStringWithContext(
+      ProtoFieldInfo field, @Nullable String string, MarshalerContext context, boolean allowEmpty)
+      throws IOException {
     if (string == null) {
       return;
     }
     if (string.isEmpty()) {
-      writeString(field, string, 0, context);
+      if (allowEmpty) {
+        writeString(field, string, 0, context);
+      }
       return;
     }
     if (context.marshalStringNoAllocation()) {

exporters/common/src/test/java/io/opentelemetry/exporter/internal/marshal/ProtoSerializerTest.java

@@ -44,7 +44,7 @@ void testSerializeEmptyStringWithContext() throws Exception {
     MarshalerContext context = new MarshalerContext();
     context.setSize(0, 0);
 
-    serializer.serializeStringWithContext(field, value, context);
+    serializer.serializeStringWithContext(field, value, context, true);
     serializer.close();
 
     byte[] result = out.toByteArray();

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/StringAnyValueMarshaler.java

@@ -33,9 +33,6 @@ static MarshalerWithSize create(String value) {
 
   @Override
   public void writeTo(Serializer output) throws IOException {
-    if (valueUtf8.length == 0) {
-      return;
-    }
     output.writeString(AnyValue.STRING_VALUE, valueUtf8);
   }
 

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/StringAnyValueStatelessMarshaler.java

@@ -26,7 +26,8 @@ private StringAnyValueStatelessMarshaler() {}
   @Override
   public void writeTo(Serializer output, String value, MarshalerContext context)
       throws IOException {
-    output.serializeStringWithContext(AnyValue.STRING_VALUE, value, context);
+    output.serializeStringWithContext(
+        AnyValue.STRING_VALUE, value, context, /* allowEmpty= */ true);
   }
 
   @Override

exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/traces/LowAllocationTraceRequestMarshalerTest.java

@@ -88,6 +88,7 @@ private static SpanData createSpanData() {
             Attributes.builder()
                 .put(KEY_BOOL, true)
                 .put(KEY_STRING, "string")
+                .put("empty", "")
                 .put(KEY_INT, 100L)
                 .put(KEY_DOUBLE, 100.3)
                 .build())