prevent NPE when calling GetResponse#getSourceAsBytesRef

This commit checks for a null BytesReference as the value for `source`
in GetResult#sourceRef and simply returns null. Previously this would
have resulted in a NPE. While this does seem internal at first glance, it can affect
user code as a GetResponse could trigger this when the document is missing.

Additionally, the CompressorFactory#uncompressIfNeeded now requires a
non-null argument.

core/src/main/java/org/elasticsearch/common/compress/CompressorFactory.java

@@ -28,6 +28,7 @@ import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentType;
 
 import java.io.IOException;
+import java.util.Objects;
 
 public class CompressorFactory {
 
@@ -68,9 +69,10 @@ public class CompressorFactory {
 
     /**
      * Uncompress the provided data, data can be detected as compressed using {@link #isCompressed(BytesReference)}.
+     * @throws NullPointerException a NullPointerException will be thrown when bytes is null
      */
     public static BytesReference uncompressIfNeeded(BytesReference bytes) throws IOException {
-        Compressor compressor = compressor(bytes);
+        Compressor compressor = compressor(Objects.requireNonNull(bytes, "the BytesReference must not be null"));
         BytesReference uncompressed;
         if (compressor != null) {
             uncompressed = uncompress(bytes, compressor);

core/src/main/java/org/elasticsearch/index/get/GetResult.java

@@ -54,7 +54,7 @@ public class GetResult implements Streamable, Iterable<GetField>, ToXContentObje
     private static final String _VERSION = "_version";
     private static final String FOUND = "found";
     private static final String FIELDS = "fields";
-    
+
     private String index;
     private String type;
     private String id;
@@ -135,6 +135,10 @@ public class GetResult implements Streamable, Iterable<GetField>, ToXContentObje
      * Returns bytes reference, also un compress the source if needed.
      */
     public BytesReference sourceRef() {
+        if (source == null) {
+            return null;
+        }
+
         try {
             this.source = CompressorFactory.uncompressIfNeeded(this.source);
             return this.source;

core/src/test/java/org/elasticsearch/index/get/GetResultTests.java

@@ -79,6 +79,17 @@ public class GetResultTests extends ESTestCase {
         }
     }
 
+    public void testGetSourceAsBytes() {
+        XContentType xContentType = randomFrom(XContentType.values());
+        Tuple<GetResult, GetResult> tuple = randomGetResult(xContentType);
+        GetResult getResult = tuple.v1();
+        if (getResult.isExists()) {
+            assertNotNull(getResult.sourceRef());
+        } else {
+            assertNull(getResult.sourceRef());
+        }
+    }
+
     public void testEqualsAndHashcode() {
         checkEqualsAndHashCode(randomGetResult(XContentType.JSON).v1(), GetResultTests::copyGetResult, GetResultTests::mutateGetResult);
     }