fix: correct field index in PerfAPI codegen when fields are filtered (#788)

When generating PerfAPI accessor methods, field indices were incorrect
if some fields were skipped (e.g., filtered reference types). The loop
index was used instead of tracking actual field positions in the schema.

Author: eduardoramirez

hollow/src/main/java/com/netflix/hollow/api/codegen/perfapi/HollowObjectTypePerfAPIClassGenerator.java

@@ -20,6 +20,9 @@
 import com.netflix.hollow.core.HollowDataset;
 import com.netflix.hollow.core.schema.HollowObjectSchema;
 import com.netflix.hollow.core.schema.HollowObjectSchema.FieldType;
+
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Set;
 
 import static com.netflix.hollow.api.codegen.HollowCodeGenerationUtils.includeType;
@@ -60,17 +63,18 @@ public String generate() {
         builder.append("\n@SuppressWarnings(\"all\")\n");
         builder.append("public class " + schema.getName() + "PerfAPI extends HollowObjectTypePerfAPI {\n\n");
 
+        List<Integer> fieldPositions = new ArrayList<>(schema.numFields());
+
         builder.append("    public static final String fieldNames[] = { ");
         int addedFields = 0;
         for(int i=0;i<schema.numFields();i++) {
-            if (dataset != null && schema.getFieldType(i) == HollowObjectSchema.FieldType.REFERENCE &&
-                !includeType(schema.getReferencedType(i), dataset)) {
+            if (dataset != null && schema.getFieldType(i) == HollowObjectSchema.FieldType.REFERENCE && !includeType(schema.getReferencedType(i), dataset)) {
                 continue;
             }
-
             if(addedFields > 0) {
                 builder.append(", ");
             }
+            fieldPositions.add(i);
             builder.append("\"").append(schema.getFieldName(i)).append("\"");
             addedFields++;
         }
@@ -81,14 +85,11 @@ public String generate() {
         builder.append("        super(dataAccess, typeName, api, fieldNames);\n");
         builder.append("    }\n\n");
 
-        for(int i=0;i<schema.numFields();i++) {
-            if (dataset != null && schema.getFieldType(i) == HollowObjectSchema.FieldType.REFERENCE && !includeType(schema.getReferencedType(i), dataset)) {
-                continue;
-            }
-
-            FieldType fieldType = schema.getFieldType(i);
-            String fieldName = schema.getFieldName(i);
-            String referencedType = schema.getReferencedType(i);
+        for(int i=0;i<fieldPositions.size();i++) {
+            int position = fieldPositions.get(i);
+            String fieldName = schema.getFieldName(position);
+            FieldType fieldType = schema.getFieldType(position);
+            String referencedType = schema.getReferencedType(position);
             appendFieldMethod(builder, fieldType, fieldName, i, referencedType);
         }
 

hollow/src/test/resources/hollow_code_gen_test.schema

@@ -13,6 +13,7 @@ TopLevelObject {
 	MapOfStringToObject2 invalidMapField1;
 	MapOfObject2ToString invalidMapField2;
 	Object2 invalidMemberField;
+	String validStringField;
 }
 
 ListOfObject1 List<Object1>;