Retain originalIndex info when rewriting FieldCapabilities requests (#27761)

A FieldCapabilities request can cover multiple indices (or aliases pointing to multiple indices).
When rewriting the request for each index, store the original requested indices.

core/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesIndexRequest.java

@@ -19,7 +19,10 @@
 
 package org.elasticsearch.action.fieldcaps;
 
+import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.action.OriginalIndices;
+import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.action.support.single.shard.SingleShardRequest;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -30,32 +33,54 @@ public class FieldCapabilitiesIndexRequest
     extends SingleShardRequest<FieldCapabilitiesIndexRequest> {
 
     private String[] fields;
+    private OriginalIndices originalIndices;
 
     // For serialization
     FieldCapabilitiesIndexRequest() {}
 
-    FieldCapabilitiesIndexRequest(String[] fields, String index) {
+    FieldCapabilitiesIndexRequest(String[] fields, String index, OriginalIndices originalIndices) {
         super(index);
         if (fields == null || fields.length == 0) {
             throw new IllegalArgumentException("specified fields can't be null or empty");
         }
         this.fields = fields;
+        assert index != null;
+        this.index(index);
+        this.originalIndices = originalIndices;
     }
 
     public String[] fields() {
         return fields;
     }
 
+    @Override
+    public String[] indices() {
+        return originalIndices.indices();
+    }
+
+    @Override
+    public IndicesOptions indicesOptions() {
+        return originalIndices.indicesOptions();
+    }
+
     @Override
     public void readFrom(StreamInput in) throws IOException {
         super.readFrom(in);
         fields = in.readStringArray();
+        if (in.getVersion().onOrAfter(Version.V_6_2_0)) {
+            originalIndices = OriginalIndices.readOriginalIndices(in);
+        } else {
+            originalIndices = OriginalIndices.NONE;
+        }
     }
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeStringArray(fields);
+        if (out.getVersion().onOrAfter(Version.V_6_2_0)) {
+            OriginalIndices.writeOriginalIndices(originalIndices, out);
+        }
     }
 
     @Override

core/src/main/java/org/elasticsearch/action/fieldcaps/TransportFieldCapabilitiesAction.java

@@ -110,7 +110,7 @@ public class TransportFieldCapabilitiesAction extends HandledTransportAction<Fie
                 }
             };
             for (String index : concreteIndices) {
-                shardAction.execute(new FieldCapabilitiesIndexRequest(request.fields(), index), innerListener);
+                shardAction.execute(new FieldCapabilitiesIndexRequest(request.fields(), index, localIndices), innerListener);
             }
 
             // this is the cross cluster part of this API - we force the other cluster to not merge the results but instead

core/src/test/java/org/elasticsearch/action/IndicesRequestIT.java

@@ -59,6 +59,8 @@ import org.elasticsearch.action.bulk.BulkRequest;
 import org.elasticsearch.action.delete.DeleteRequest;
 import org.elasticsearch.action.explain.ExplainAction;
 import org.elasticsearch.action.explain.ExplainRequest;
+import org.elasticsearch.action.fieldcaps.FieldCapabilitiesAction;
+import org.elasticsearch.action.fieldcaps.FieldCapabilitiesRequest;
 import org.elasticsearch.action.get.GetAction;
 import org.elasticsearch.action.get.GetRequest;
 import org.elasticsearch.action.get.MultiGetAction;
@@ -188,6 +190,19 @@ public class IndicesRequestIT extends ESIntegTestCase {
         assertSameIndices(getFieldMappingsRequest, getFieldMappingsShardAction);
     }
 
+    public void testFieldCapabilities() {
+        String fieldCapabilitiesShardAction = FieldCapabilitiesAction.NAME + "[index][s]";
+        interceptTransportActions(fieldCapabilitiesShardAction);
+
+        FieldCapabilitiesRequest fieldCapabilitiesRequest = new FieldCapabilitiesRequest();
+        fieldCapabilitiesRequest.indices(randomIndicesOrAliases());
+        fieldCapabilitiesRequest.fields(randomAlphaOfLength(8));
+        internalCluster().coordOnlyNodeClient().fieldCaps(fieldCapabilitiesRequest).actionGet();
+
+        clearInterceptedActions();
+        assertSameIndices(fieldCapabilitiesRequest, fieldCapabilitiesShardAction);
+    }
+
     public void testAnalyze() {
         String analyzeShardAction = AnalyzeAction.NAME + "[s]";
         interceptTransportActions(analyzeShardAction);