Fix NPE during search with source filtering if the source is disabled. (#20093)

* Fix NPE during search with source filtering if the source is disabled.
Instead of throwing an NPE, a search response with source filtering will not contain the source if it is disabled in the mapping.

Closes #7758

* Created unit tests for FetchSourceSubPhase. Tests similar to SourceFetchingIT.
Removed SourceFetchingIT#testSourceDisabled (now covered via unit test FetchSourceSubPhaseTests#testSourceDisabled).

* Updated FetchSouceSubPhase unit tests per comments.
Renamed main unit test method.
Use assertEquals and assertNull instead of assertThat (less code).

core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceSubPhase.java

@@ -35,19 +35,22 @@ public final class FetchSourceSubPhase implements FetchSubPhase {
         if (context.sourceRequested() == false) {
             return;
         }
+        SourceLookup source = context.lookup().source();
+        if (source.internalSourceRef() == null) {
+            return; // source disabled in the mapping
+        }
         FetchSourceContext fetchSourceContext = context.fetchSourceContext();
         assert fetchSourceContext.fetchSource();
         if (fetchSourceContext.includes().length == 0 && fetchSourceContext.excludes().length == 0) {
-            hitContext.hit().sourceRef(context.lookup().source().internalSourceRef());
+            hitContext.hit().sourceRef(source.internalSourceRef());
             return;
         }
 
-        SourceLookup source = context.lookup().source();
         Object value = source.filter(fetchSourceContext.includes(), fetchSourceContext.excludes());
         try {
             final int initialCapacity = Math.min(1024, source.internalSourceRef().length());
             BytesStreamOutput streamOutput = new BytesStreamOutput(initialCapacity);
-            XContentBuilder builder = new XContentBuilder(context.lookup().source().sourceContentType().xContent(), streamOutput);
+            XContentBuilder builder = new XContentBuilder(source.sourceContentType().xContent(), streamOutput);
             builder.value(value);
             hitContext.hit().sourceRef(builder.bytes());
         } catch (IOException e) {

core/src/test/java/org/elasticsearch/search/fetch/subphase/FetchSourceSubPhaseTests.java

@@ -0,0 +1,134 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.search.fetch.subphase;
+
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.bytes.BytesReference;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.search.fetch.FetchSubPhase;
+import org.elasticsearch.search.internal.InternalSearchHit;
+import org.elasticsearch.search.internal.SearchContext;
+import org.elasticsearch.search.lookup.SearchLookup;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.test.TestSearchContext;
+
+import java.io.IOException;
+import java.util.Collections;
+
+public class FetchSourceSubPhaseTests extends ESTestCase {
+
+    static class FetchSourceSubPhaseTestSearchContext extends TestSearchContext {
+
+        FetchSourceContext context;
+        BytesReference source;
+
+        FetchSourceSubPhaseTestSearchContext(FetchSourceContext context, BytesReference source) {
+            super(null);
+            this.context = context;
+            this.source = source;
+        }
+
+        @Override
+        public boolean sourceRequested() {
+            return context != null && context.fetchSource();
+        }
+
+        @Override
+        public FetchSourceContext fetchSourceContext() {
+            return context;
+        }
+
+        @Override
+        public SearchLookup lookup() {
+            SearchLookup lookup = super.lookup();
+            lookup.source().setSource(source);
+            return lookup;
+        }
+    }
+
+    public void testFetchSource() throws IOException {
+        XContentBuilder source = XContentFactory.jsonBuilder().startObject()
+            .field("field", "value")
+            .endObject();
+        FetchSubPhase.HitContext hitContext = hitExecute(source, true, null, null);
+        assertEquals(Collections.singletonMap("field","value"), hitContext.hit().sourceAsMap());
+    }
+
+    public void testBasicFiltering() throws IOException {
+        XContentBuilder source = XContentFactory.jsonBuilder().startObject()
+            .field("field1", "value")
+            .field("field2", "value2")
+            .endObject();
+        FetchSubPhase.HitContext hitContext = hitExecute(source, false, null, null);
+        assertNull(hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecute(source, true, "field1", null);
+        assertEquals(Collections.singletonMap("field1","value"), hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecute(source, true, "hello", null);
+        assertEquals(Collections.emptyMap(), hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecute(source, true, "*", "field2");
+        assertEquals(Collections.singletonMap("field1","value"), hitContext.hit().sourceAsMap());
+    }
+
+    public void testMultipleFiltering() throws IOException {
+        XContentBuilder source = XContentFactory.jsonBuilder().startObject()
+            .field("field", "value")
+            .field("field2", "value2")
+            .endObject();
+        FetchSubPhase.HitContext hitContext = hitExecuteMultiple(source, true, new String[]{"*.notexisting", "field"}, null);
+        assertEquals(Collections.singletonMap("field","value"), hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecuteMultiple(source, true, new String[]{"field.notexisting.*", "field"}, null);
+        assertEquals(Collections.singletonMap("field","value"), hitContext.hit().sourceAsMap());
+    }
+
+    public void testSourceDisabled() throws IOException {
+        FetchSubPhase.HitContext hitContext = hitExecute(null, true, null, null);
+        assertNull(hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecute(null, false, null, null);
+        assertNull(hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecute(null, true, "field1", null);
+        assertNull(hitContext.hit().sourceAsMap());
+
+        hitContext = hitExecuteMultiple(null, true, new String[]{"*"}, new String[]{"field2"});
+        assertNull(hitContext.hit().sourceAsMap());
+    }
+
+    private FetchSubPhase.HitContext hitExecute(XContentBuilder source, boolean fetchSource, String include, String exclude) {
+        return hitExecuteMultiple(source, fetchSource,
+            include == null ? Strings.EMPTY_ARRAY : new String[]{include},
+            exclude == null ? Strings.EMPTY_ARRAY : new String[]{exclude});
+    }
+
+    private FetchSubPhase.HitContext hitExecuteMultiple(XContentBuilder source, boolean fetchSource, String[] includes, String[] excludes) {
+        FetchSourceContext fetchSourceContext = new FetchSourceContext(fetchSource, includes, excludes);
+        SearchContext searchContext = new FetchSourceSubPhaseTestSearchContext(fetchSourceContext, source == null ? null : source.bytes());
+        FetchSubPhase.HitContext hitContext = new FetchSubPhase.HitContext();
+        hitContext.reset(new InternalSearchHit(1, null, null, null), null, 1, null);
+        FetchSourceSubPhase phase = new FetchSourceSubPhase();
+        phase.hitExecute(searchContext, hitContext);
+        return hitContext;
+    }
+}