Fix get source HEAD requests

Get source HEAD requests incorrectly return a content-length header of
0. This commit addresses this by removing the special handling for get
source HEAD requests, and just relying on the general mechanism that
exists for handling HEAD requests in the REST layer.

Relates #23151

2 files changed, 17 insertions, 26 deletions

diff --git a/core/src/main/java/org/elasticsearch/rest/action/document/RestGetSourceAction.java b/core/src/main/java/org/elasticsearch/rest/action/document/RestGetSourceAction.java
index 83d424ed74..341c1ddc91 100644
--- a/core/src/main/java/org/elasticsearch/rest/action/document/RestGetSourceAction.java
+++ b/core/src/main/java/org/elasticsearch/rest/action/document/RestGetSourceAction.java
@@ -36,13 +36,19 @@ import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 import java.io.IOException;
 
 import static org.elasticsearch.rest.RestRequest.Method.GET;
+import static org.elasticsearch.rest.RestRequest.Method.HEAD;
 import static org.elasticsearch.rest.RestStatus.NOT_FOUND;
 import static org.elasticsearch.rest.RestStatus.OK;
 
+/**
+ * The REST handler for get source and head source APIs.
+ */
 public class RestGetSourceAction extends BaseRestHandler {
-    public RestGetSourceAction(Settings settings, RestController controller) {
+
+    public RestGetSourceAction(final Settings settings, final RestController controller) {
         super(settings);
         controller.registerHandler(GET, "/{index}/{type}/{id}/_source", this);
+        controller.registerHandler(HEAD, "/{index}/{type}/{id}/_source", this);
     }
 
     @Override
@@ -50,7 +56,7 @@ public class RestGetSourceAction extends BaseRestHandler {
         final GetRequest getRequest = new GetRequest(request.param("index"), request.param("type"), request.param("id"));
         getRequest.operationThreaded(true);
         getRequest.refresh(request.paramAsBoolean("refresh", getRequest.refresh()));
-        getRequest.routing(request.param("routing"));  // order is important, set it after routing, so it will set the routing
+        getRequest.routing(request.param("routing"));
         getRequest.parent(request.param("parent"));
         getRequest.preference(request.param("preference"));
         getRequest.realtime(request.paramAsBoolean("realtime", getRequest.realtime()));
@@ -59,15 +65,16 @@ public class RestGetSourceAction extends BaseRestHandler {
 
         return channel -> {
             if (getRequest.fetchSourceContext() != null && !getRequest.fetchSourceContext().fetchSource()) {
-                ActionRequestValidationException validationError = new ActionRequestValidationException();
+                final ActionRequestValidationException validationError = new ActionRequestValidationException();
                 validationError.addValidationError("fetching source can not be disabled");
                 channel.sendResponse(new BytesRestResponse(channel, validationError));
             } else {
                 client.get(getRequest, new RestResponseListener<GetResponse>(channel) {
                     @Override
-                    public RestResponse buildResponse(GetResponse response) throws Exception {
-                        XContentBuilder builder = channel.newBuilder(request.getXContentType(), false);
-                        if (response.isSourceEmpty()) { // check if doc source (or doc itself) is missing
+                    public RestResponse buildResponse(final GetResponse response) throws Exception {
+                        final XContentBuilder builder = channel.newBuilder(request.getXContentType(), false);
+                        // check if doc source (or doc itself) is missing
+                        if (response.isSourceEmpty()) {
                             return new BytesRestResponse(NOT_FOUND, builder);
                         } else {
                             builder.rawValue(response.getSourceInternal());
@@ -78,4 +85,5 @@ public class RestGetSourceAction extends BaseRestHandler {
             }
         };
     }
+
 }
diff --git a/core/src/main/java/org/elasticsearch/rest/action/document/RestHeadAction.java b/core/src/main/java/org/elasticsearch/rest/action/document/RestHeadAction.java
index cc90b2cfa0..14e412aebe 100644
--- a/core/src/main/java/org/elasticsearch/rest/action/document/RestHeadAction.java
+++ b/core/src/main/java/org/elasticsearch/rest/action/document/RestHeadAction.java
@@ -48,33 +48,18 @@ public abstract class RestHeadAction extends BaseRestHandler {
      */
     public static class Document extends RestHeadAction {
         public Document(Settings settings, RestController controller) {
-            super(settings, false);
+            super(settings);
             controller.registerHandler(HEAD, "/{index}/{type}/{id}", this);
         }
     }
 
     /**
-     * Handler to check for document source existence (may be disabled in the mapping).
-     */
-    public static class Source extends RestHeadAction {
-        public Source(Settings settings, RestController controller) {
-            super(settings, true);
-            controller.registerHandler(HEAD, "/{index}/{type}/{id}/_source", this);
-        }
-    }
-
-    private final boolean source;
-
-    /**
      * All subclasses must be registered in {@link org.elasticsearch.common.network.NetworkModule}.
+     *  @param settings injected settings
      *
-     * @param settings injected settings
-     * @param source   {@code false} to check for {@link GetResponse#isExists()}.
-     *                 {@code true} to also check for {@link GetResponse#isSourceEmpty()}.
      */
-    public RestHeadAction(Settings settings, boolean source) {
+    public RestHeadAction(Settings settings) {
         super(settings);
-        this.source = source;
     }
 
     @Override
@@ -95,8 +80,6 @@ public abstract class RestHeadAction extends BaseRestHandler {
             public RestResponse buildResponse(GetResponse response) {
                 if (!response.isExists()) {
                     return new BytesRestResponse(NOT_FOUND, BytesRestResponse.TEXT_CONTENT_TYPE, BytesArray.EMPTY);
-                } else if (source && response.isSourceEmpty()) { // doc exists, but source might not (disabled in the mapping)
-                    return new BytesRestResponse(NOT_FOUND, BytesRestResponse.TEXT_CONTENT_TYPE, BytesArray.EMPTY);
                 } else {
                     return new BytesRestResponse(OK, BytesRestResponse.TEXT_CONTENT_TYPE, BytesArray.EMPTY);
                 }