Add status field to MultiSearchTemplateResponse (elastic#85496)

This change adds a `status` field to MultiSearchTemplateResponse items, 
as is already the case for MultiSearchResponse, making the two response
formats consistent.

Closes elastic#83029

docs/changelog/85496.yaml

@@ -0,0 +1,6 @@
+pr: 85496
+summary: Add status field to Multi Search Template Responses
+area: Search
+type: bug
+issues:
+  - 83029

modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/MultiSearchTemplateResponse.java

@@ -9,6 +9,7 @@
 package org.elasticsearch.script.mustache;
 
 import org.elasticsearch.ElasticsearchException;
+import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.search.MultiSearchResponse;
@@ -146,13 +147,15 @@ public XContentBuilder toXContent(XContentBuilder builder, ToXContent.Params par
         builder.field("took", tookInMillis);
         builder.startArray(Fields.RESPONSES);
         for (Item item : items) {
+            builder.startObject();
             if (item.isFailure()) {
-                builder.startObject();
                 ElasticsearchException.generateFailureXContent(builder, params, item.getFailure(), true);
-                builder.endObject();
+                builder.field(Fields.STATUS, ExceptionsHelper.status(item.getFailure()).getStatus());
             } else {
-                item.getResponse().toXContent(builder, params);
+                item.getResponse().innerToXContent(builder, params);
+                builder.field(Fields.STATUS, item.getResponse().status().getStatus());
             }
+            builder.endObject();
         }
         builder.endArray();
         builder.endObject();
@@ -161,6 +164,7 @@ public XContentBuilder toXContent(XContentBuilder builder, ToXContent.Params par
 
     static final class Fields {
         static final String RESPONSES = "responses";
+        static final String STATUS = "status";
     }
 
     public static MultiSearchTemplateResponse fromXContext(XContentParser parser) {

modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/SearchTemplateResponse.java

@@ -95,15 +95,20 @@ public static SearchTemplateResponse fromXContent(XContentParser parser) throws
 
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject();
+        innerToXContent(builder, params);
+        builder.endObject();
+        return builder;
+    }
+
+    public XContentBuilder innerToXContent(XContentBuilder builder, Params params) throws IOException {
         if (hasResponse()) {
-            response.toXContent(builder, params);
+            response.innerToXContent(builder, params);
         } else {
-            builder.startObject();
             // we can assume the template is always json as we convert it before compiling it
             try (InputStream stream = source.streamInput()) {
                 builder.rawField(TEMPLATE_OUTPUT_FIELD.getPreferredName(), stream, XContentType.JSON);
             }
-            builder.endObject();
         }
         return builder;
     }

modules/lang-mustache/src/yamlRestTest/resources/rest-api-spec/test/lang_mustache/50_multi_search_template.yml

@@ -31,6 +31,10 @@ setup:
 ---
 "Basic multi-search template":
 
+  - skip:
+      version: " - 8.2.99"
+      reason:  "status field checks were added in 8.3"
+
   - do:
       msearch_template:
         rest_total_hits_as_int: true
@@ -62,10 +66,18 @@ setup:
   - match:  { responses.2.hits.total:     4  }
   - match:  { responses.3.hits.total:     1  }
   - length: { responses.3.hits.hits:      0  }
+  - match:  { responses.0.status: 200 }
+  - match:  { responses.1.status: 200 }
+  - match:  { responses.2.status: 200 }
+  - match:  { responses.3.status: 200 }
 
 
 ---
 "Multi-search template with errors":
+
+  - skip:
+      version: " - 8.2.99"
+      reason:  "status field checks were added in 8.3"
 
   - do:
       msearch_template:
@@ -108,6 +120,10 @@ setup:
   - match:  { responses.3.error.root_cause.0.reason: "/unknown.query.\\[unknown\\]/" }
   - match:  { responses.4.error.root_cause.0.type: illegal_argument_exception }
   - match:  { responses.4.error.root_cause.0.reason: "[rest_total_hits_as_int] cannot be used if the tracking of total hits is not accurate, got 1" }
+  - match:  { responses.0.status: 200 }
+  - match:  { responses.1.status: 500 }
+  - match:  { responses.2.status: 200 }
+  - match:  { responses.3.status: 400 }
 
 
 ---
@@ -135,6 +151,10 @@ setup:
 ---
 "Basic multi-search using stored template":
 
+  - skip:
+      version: " - 8.2.99"
+      reason:  "status field checks were added in 8.3"
+
   - do:
       put_script:
         id: stored_template_1
@@ -164,7 +184,9 @@ setup:
   - match:  { responses.0.hits.total:     2  }
   - match:  { responses.1.hits.total:     1  }
   - match:  { responses.2.hits.total:     1  }
-
+  - match:  { responses.0.status: 200 }
+  - match:  { responses.1.status: 200 }
+  - match:  { responses.2.status: 200 }
 
   - do:
       put_script:
@@ -174,6 +196,11 @@ setup:
 
 ---
 "Test with rest_total_hits_as_int":
+
+  - skip:
+      version: " - 8.2.99"
+      reason:  "status field checks were added in 8.3"
+
   - do:
       put_script:
         id: stored_template_1
@@ -205,3 +232,6 @@ setup:
   - match:  { responses.1.hits.total.relation:  eq }
   - match:  { responses.2.hits.total.value:     1  }
   - match:  { responses.1.hits.total.relation:  eq }
+  - match:  { responses.0.status: 200 }
+  - match:  { responses.1.status: 200 }
+  - match:  { responses.2.status: 200 }