Fix writeString(char[],int,int) writing enum values twice

protobuf/src/main/java/tools/jackson/dataformat/protobuf/ProtobufGenerator.java

@@ -896,6 +896,7 @@ public JsonGenerator writeString(char[] text, int offset, int clen) throws Jacks
         }
         if (_currField.wireType != WireType.LENGTH_PREFIXED) {
             _writeEnum(new String(text, offset, clen));
+            return this;
         }
 
         // Could guarantee with 42 chars or less; but let's do bit more speculative

protobuf/src/test/java/tools/jackson/dataformat/protobuf/WriteEnumAsCharArrayTest.java

@@ -0,0 +1,62 @@
+package tools.jackson.dataformat.protobuf;
+
+import java.io.ByteArrayOutputStream;
+
+import org.junit.jupiter.api.Test;
+
+import tools.jackson.core.JsonGenerator;
+
+import tools.jackson.dataformat.protobuf.schema.ProtobufSchema;
+import tools.jackson.dataformat.protobuf.schema.ProtobufSchemaLoader;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Tests for writing enum-valued fields through the {@code char[]} variant of
+ * {@code writeString()}, which used to fall through and additionally emit the
+ * value as a length-prefixed String.
+ */
+public class WriteEnumAsCharArrayTest extends ProtobufTestBase
+{
+    private final ProtobufMapper MAPPER = newObjectMapper();
+
+    @Test
+    public void testEnumViaCharArrayMatchesString() throws Exception
+    {
+        ProtobufSchema schema = ProtobufSchemaLoader.std.parse(PROTOC_SEARCH_REQUEST);
+
+        byte[] viaString = _write(schema, false);
+        byte[] viaCharArray = _write(schema, true);
+
+        // 1 byte for tag, 1 byte for enum index -- nothing more
+        assertEquals(2, viaString.length);
+        assertArrayEquals(viaString, viaCharArray);
+    }
+
+    @Test
+    public void testEnumViaCharArrayRoundTrips() throws Exception
+    {
+        ProtobufSchema schema = ProtobufSchemaLoader.std.parse(PROTOC_SEARCH_REQUEST);
+        SearchRequest result = MAPPER.readerFor(SearchRequest.class).with(schema)
+                .readValue(_write(schema, true));
+        assertEquals(Corpus.WEB, result.corpus);
+    }
+
+    private byte[] _write(ProtobufSchema schema, boolean useCharArray) throws Exception
+    {
+        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+        try (JsonGenerator g = MAPPER.writer(schema).createGenerator(bytes)) {
+            g.writeStartObject();
+            g.writeName("corpus");
+            if (useCharArray) {
+                char[] ch = "WEB".toCharArray();
+                g.writeString(ch, 0, ch.length);
+            } else {
+                g.writeString("WEB");
+            }
+            g.writeEndObject();
+        }
+        return bytes.toByteArray();
+    }
+}

release-notes/CREDITS

@@ -76,3 +76,6 @@ PJ Fanning (@pjfanning)
 * Contributed #763: (protobuf) Use `VarHandle` for multi-byte primitive reads
   and writes in `ProtobufParser` / `ProtobufGenerator`
  (3.3.0)
+* Contributed #772: (protobuf) `ProtobufGenerator.writeString(char[],int,int)`
+  writes enum values twice
+ (3.3.0)

release-notes/VERSION

@@ -38,6 +38,9 @@ implementations)
 #767: (smile) Use more efficient `String` construction wrt "Compact Strings"
   for "short" ASCII text values of async parser
  (fix by @cowtowncoder, w/ Claude code)
+#772: (protobuf) `ProtobufGenerator.writeString(char[],int,int)` writes enum
+  values twice
+ (contributed by @pjfanning)
 
 3.2.3 (not yet released)