Add Shrink request source parser to parse create index request body

Follow up to https://github.com/elastic/elasticsearch/pull/18732#discussion_r66407196

core/src/main/java/org/elasticsearch/action/admin/indices/shrink/ShrinkRequest.java

@@ -18,15 +18,25 @@
  */
 package org.elasticsearch.action.admin.indices.shrink;
 
+import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.admin.indices.create.CreateIndexRequest;
 import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.action.support.master.AcknowledgedRequest;
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.ParseFieldMatcher;
+import org.elasticsearch.common.ParseFieldMatcherSupplier;
+import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.xcontent.ObjectParser;
+import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.common.xcontent.XContentType;
 
 import java.io.IOException;
+import java.util.Map;
 import java.util.Objects;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
@@ -36,6 +46,17 @@ import static org.elasticsearch.action.ValidateActions.addValidationError;
  */
 public class ShrinkRequest extends AcknowledgedRequest<ShrinkRequest> implements IndicesRequest {
 
+    public static ObjectParser<ShrinkRequest, ParseFieldMatcherSupplier> PARSER =
+        new ObjectParser<>("shrink_request", null);
+    static {
+        PARSER.declareField((parser, request, parseFieldMatcherSupplier) ->
+                request.getShrinkIndexRequest().settings(parser.map()),
+            new ParseField("settings"), ObjectParser.ValueType.OBJECT);
+        PARSER.declareField((parser, request, parseFieldMatcherSupplier) ->
+                request.getShrinkIndexRequest().aliases(parser.map()),
+            new ParseField("aliases"), ObjectParser.ValueType.OBJECT);
+    }
+
     private CreateIndexRequest shrinkIndexRequest;
     private String sourceIndex;
 
@@ -104,4 +125,17 @@ public class ShrinkRequest extends AcknowledgedRequest<ShrinkRequest> implements
     public String getSourceIndex() {
         return sourceIndex;
     }
+
+    public void source(BytesReference source) {
+        XContentType xContentType = XContentFactory.xContentType(source);
+        if (xContentType != null) {
+            try (XContentParser parser = XContentFactory.xContent(xContentType).createParser(source)) {
+                PARSER.parse(parser, this, () -> ParseFieldMatcher.EMPTY);
+            } catch (IOException e) {
+                throw new ElasticsearchParseException("failed to parse source for shrink index", e);
+            }
+        } else {
+            throw new ElasticsearchParseException("failed to parse content type for shrink index source");
+        }
+    }
 }

core/src/main/java/org/elasticsearch/rest/action/admin/indices/RestShrinkIndexAction.java

@@ -52,7 +52,7 @@ public class RestShrinkIndexAction extends BaseRestHandler {
         }
         ShrinkRequest shrinkIndexRequest = new ShrinkRequest(request.param("target"), request.param("index"));
         if (request.hasContent()) {
-            shrinkIndexRequest.getShrinkIndexRequest().source(request.content());
+            shrinkIndexRequest.source(request.content());
         }
         shrinkIndexRequest.timeout(request.paramAsTime("timeout", shrinkIndexRequest.timeout()));
         shrinkIndexRequest.masterNodeTimeout(request.paramAsTime("master_timeout", shrinkIndexRequest.masterNodeTimeout()));

rest-api-spec/src/main/resources/rest-api-spec/test/indices.shrink/10_basic.yaml

@@ -54,7 +54,8 @@
         index: "source"
         target: "target"
         body:
-          index.number_of_replicas: 0
+          settings:
+            index.number_of_replicas: 0
 
   - do:
       cluster.health: