Repsect indices options on _msearch (#35887)

Today we don't respect the indices options when they are passed
as request parameters to the `_msearch` endpoint. This is unintuitive
and doesn't cause any errors. This changes uses the top-level indices
options as the defaults for each sub search-request.

Closes #35851

server/src/main/java/org/elasticsearch/action/search/MultiSearchRequest.java

@@ -205,7 +205,7 @@ public class MultiSearchRequest extends ActionRequest implements CompositeIndice
             if (searchType != null) {
                 searchRequest.searchType(searchType);
             }
-            IndicesOptions defaultOptions = SearchRequest.DEFAULT_INDICES_OPTIONS;
+            IndicesOptions defaultOptions = searchRequest.indicesOptions();
             // now parse the action
             if (nextMarker - from > 0) {
                 try (InputStream stream = data.slice(from, nextMarker - from).streamInput();
@@ -230,7 +230,10 @@ public class MultiSearchRequest extends ActionRequest implements CompositeIndice
                             searchRequest.routing(nodeStringValue(value, null));
                         } else if ("allow_partial_search_results".equals(entry.getKey())) {
                             searchRequest.allowPartialSearchResults(nodeBooleanValue(value, null));
+                        } else {
+                            // TODO we should not be lenient here and fail if there is any unknown key in the source map
                         }
+
                     }
                     defaultOptions = IndicesOptions.fromMap(source, defaultOptions);
                 }

server/src/main/java/org/elasticsearch/rest/action/search/RestMultiSearchAction.java

@@ -86,6 +86,8 @@ public class RestMultiSearchAction extends BaseRestHandler {
      */
     public static MultiSearchRequest parseRequest(RestRequest restRequest, boolean allowExplicitIndex) throws IOException {
         MultiSearchRequest multiRequest = new MultiSearchRequest();
+        IndicesOptions indicesOptions = IndicesOptions.fromRequest(restRequest, multiRequest.indicesOptions());
+        multiRequest.indicesOptions(indicesOptions);
         if (restRequest.hasParam("max_concurrent_searches")) {
             multiRequest.maxConcurrentSearchRequests(restRequest.paramAsInt("max_concurrent_searches", 0));
         }

server/src/test/java/org/elasticsearch/action/search/MultiSearchRequestTests.java

@@ -41,6 +41,7 @@ import org.elasticsearch.test.rest.FakeRestRequest;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import static java.util.Collections.singletonList;
@@ -102,6 +103,21 @@ public class MultiSearchRequestTests extends ESTestCase {
         assertThat(request.requests().get(0).types().length, equalTo(0));
     }
 
+    public void testDefaultIndicesOptions() throws IOException {
+        final String requestContent = "{\"index\":\"test\", \"expand_wildcards\" : \"open,closed\"}}\r\n" +
+            "{\"query\" : {\"match_all\" :{}}}\r\n";
+        FakeRestRequest restRequest = new FakeRestRequest.Builder(xContentRegistry())
+            .withContent(new BytesArray(requestContent), XContentType.JSON)
+            .withParams(Collections.singletonMap("ignore_unavailable", "true"))
+            .build();
+        MultiSearchRequest request = RestMultiSearchAction.parseRequest(restRequest, true);
+        assertThat(request.requests().size(), equalTo(1));
+        assertThat(request.requests().get(0).indices()[0], equalTo("test"));
+        assertThat(request.requests().get(0).indicesOptions(),
+            equalTo(IndicesOptions.fromOptions(true, true, true, true, SearchRequest.DEFAULT_INDICES_OPTIONS)));
+        assertThat(request.requests().get(0).types().length, equalTo(0));
+    }
+
     public void testSimpleAdd2() throws Exception {
         MultiSearchRequest request = parseMultiSearchRequest("/org/elasticsearch/action/search/simple-msearch2.json");
         assertThat(request.requests().size(), equalTo(5));