Fix NPE in _listAddAll when server returns JSON null for a list field

CHANGELOG.md

@@ -23,6 +23,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Add document lifecycle guide and runnable sample ([#2017](https://github.com/opensearch-project/opensearch-java/pull/2017))
 
 ### Fixed
+- Fix `NullPointerException` in `_listAddAll` when server returns JSON `null` for a list field ([#2041](https://github.com/opensearch-project/opensearch-java/pull/2041))
 
 ## [Unreleased 3.x]
 ### Added

java-client/src/generated/java/org/opensearch/client/opensearch/core/search/ShardProfile.java

@@ -64,8 +64,8 @@ public class ShardProfile implements PlainJsonSerializable, ToCopyableBuilder<Sh
     @Nonnull
     private final List<AggregationProfile> aggregations;
 
-    @Nullable
-    private final FetchProfile fetch;
+    @Nonnull
+    private final List<FetchProfile> fetch;
 
     @Nonnull
     private final String id;
@@ -77,7 +77,7 @@ public class ShardProfile implements PlainJsonSerializable, ToCopyableBuilder<Sh
 
     private ShardProfile(Builder builder) {
         this.aggregations = ApiTypeHelper.unmodifiableRequired(builder.aggregations, this, "aggregations");
-        this.fetch = builder.fetch;
+        this.fetch = ApiTypeHelper.unmodifiable(builder.fetch);
         this.id = ApiTypeHelper.requireNonNull(builder.id, this, "id");
         this.searches = ApiTypeHelper.unmodifiableRequired(builder.searches, this, "searches");
     }
@@ -97,8 +97,8 @@ public final List<AggregationProfile> aggregations() {
     /**
      * API name: {@code fetch}
      */
-    @Nullable
-    public final FetchProfile fetch() {
+    @Nonnull
+    public final List<FetchProfile> fetch() {
         return this.fetch;
     }
 
@@ -136,9 +136,13 @@ protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
         }
         generator.writeEnd();
 
-        if (this.fetch != null) {
+        if (ApiTypeHelper.isDefined(this.fetch)) {
             generator.writeKey("fetch");
-            this.fetch.serialize(generator, mapper);
+            generator.writeStartArray();
+            for (FetchProfile item0 : this.fetch) {
+                item0.serialize(generator, mapper);
+            }
+            generator.writeEnd();
         }
 
         generator.writeKey("id");
@@ -171,22 +175,22 @@ public static Builder builder() {
     public static class Builder extends ObjectBuilderBase implements CopyableBuilder<Builder, ShardProfile> {
         private List<AggregationProfile> aggregations;
         @Nullable
-        private FetchProfile fetch;
+        private List<FetchProfile> fetch;
         private String id;
         private List<SearchProfile> searches;
 
         public Builder() {}
 
         private Builder(ShardProfile o) {
             this.aggregations = _listCopy(o.aggregations);
-            this.fetch = o.fetch;
+            this.fetch = _listCopy(o.fetch);
             this.id = o.id;
             this.searches = _listCopy(o.searches);
         }
 
         private Builder(Builder o) {
             this.aggregations = _listCopy(o.aggregations);
-            this.fetch = o.fetch;
+            this.fetch = _listCopy(o.fetch);
             this.id = o.id;
             this.searches = _listCopy(o.searches);
         }
@@ -237,15 +241,36 @@ public final Builder aggregations(Function<AggregationProfile.Builder, ObjectBui
 
         /**
          * API name: {@code fetch}
+         *
+         * <p>
+         * Adds all elements of <code>list</code> to <code>fetch</code>.
+         * </p>
+         */
+        @Nonnull
+        public final Builder fetch(List<FetchProfile> list) {
+            this.fetch = _listAddAll(this.fetch, list);
+            return this;
+        }
+
+        /**
+         * API name: {@code fetch}
+         *
+         * <p>
+         * Adds one or more values to <code>fetch</code>.
+         * </p>
          */
         @Nonnull
-        public final Builder fetch(@Nullable FetchProfile value) {
-            this.fetch = value;
+        public final Builder fetch(FetchProfile value, FetchProfile... values) {
+            this.fetch = _listAdd(this.fetch, value, values);
             return this;
         }
 
         /**
          * API name: {@code fetch}
+         *
+         * <p>
+         * Adds a value to <code>fetch</code> using a builder lambda.
+         * </p>
          */
         @Nonnull
         public final Builder fetch(Function<FetchProfile.Builder, ObjectBuilder<FetchProfile>> fn) {
@@ -325,7 +350,7 @@ public ShardProfile build() {
 
     protected static void setupShardProfileDeserializer(ObjectDeserializer<ShardProfile.Builder> op) {
         op.add(Builder::aggregations, JsonpDeserializer.arrayDeserializer(AggregationProfile._DESERIALIZER), "aggregations");
-        op.add(Builder::fetch, FetchProfile._DESERIALIZER, "fetch");
+        op.add(Builder::fetch, JsonpDeserializer.arrayDeserializer(FetchProfile._DESERIALIZER), "fetch");
         op.add(Builder::id, JsonpDeserializer.stringDeserializer(), "id");
         op.add(Builder::searches, JsonpDeserializer.arrayDeserializer(SearchProfile._DESERIALIZER), "searches");
     }

java-client/src/main/java/org/opensearch/client/util/ObjectBuilderBase.java

@@ -95,10 +95,15 @@ protected static <T> List<T> _listAdd(List<T> list, T value, T... values) {
 
     /** Add all elements of a list to a (possibly {@code null}) list */
     protected static <T> List<T> _listAddAll(List<T> list, List<T> values) {
+        if (values == null) {
+            // Server returned JSON null for a list field; treat as empty to avoid NPE.
+            // See https://github.com/opensearch-project/opensearch-java/issues/1813
+            return list;
+        }
         if (list == null) {
             // Keep the original list to avoid an unnecessary copy.
             // It will be copied if we add more values.
-            return Objects.requireNonNull(values);
+            return values;
         } else {
             list = _mutableList(list);
             list.addAll(values);

java-codegen/opensearch-openapi.yaml

@@ -52512,7 +52512,9 @@ components:
           items:
             $ref: '#/components/schemas/_core.search___SearchProfile'
         fetch:
-          $ref: '#/components/schemas/_core.search___FetchProfile'
+          type: array
+          items:
+            $ref: '#/components/schemas/_core.search___FetchProfile'
       required:
         - aggregations
         - id