Share XContent rendering code in terms aggs (#23680)

The output of the different implementations of terms aggs is always very similar. The toXContent methods for each of those classes though was duplicating almost the same code multiple times. This commit centralizes the code for rendering XContent to a single place, which can be reused from the different terms aggs implementations.

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/DoubleTerms.java

@@ -86,18 +86,11 @@ public class DoubleTerms extends InternalMappedTerms<DoubleTerms, DoubleTerms.Bu
         }
 
         @Override
-        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-            builder.startObject();
+        protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
             builder.field(CommonFields.KEY, term);
             if (format != DocValueFormat.RAW) {
                 builder.field(CommonFields.KEY_AS_STRING, format.format(term));
             }
-            builder.field(CommonFields.DOC_COUNT, getDocCount());
-            if (showDocCountError) {
-                builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, getDocCountError());
-            }
-            aggregations.toXContentInternal(builder, params);
-            builder.endObject();
             return builder;
         }
 
@@ -149,18 +142,6 @@ public class DoubleTerms extends InternalMappedTerms<DoubleTerms, DoubleTerms.Bu
                 shardSize, showTermDocCountError, otherDocCount, buckets, docCountError);
     }
 
-    @Override
-    public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, docCountError);
-        builder.field(SUM_OF_OTHER_DOC_COUNTS, otherDocCount);
-        builder.startArray(CommonFields.BUCKETS);
-        for (Bucket bucket : buckets) {
-            bucket.toXContent(builder, params);
-        }
-        builder.endArray();
-        return builder;
-    }
-
     @Override
     protected Bucket[] createBucketsArray(int size) {
         return new Bucket[size];
@@ -171,7 +152,7 @@ public class DoubleTerms extends InternalMappedTerms<DoubleTerms, DoubleTerms.Bu
         boolean promoteToDouble = false;
         for (InternalAggregation agg : aggregations) {
             if (agg instanceof LongTerms && ((LongTerms) agg).format == DocValueFormat.RAW) {
-                /**
+                /*
                  * this terms agg mixes longs and doubles, we must promote longs to doubles to make the internal aggs
                  * compatible
                  */

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/GlobalOrdinalsStringTermsAggregator.java

@@ -246,7 +246,7 @@ public class GlobalOrdinalsStringTermsAggregator extends AbstractStringTermsAggr
         }
 
         @Override
-        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
             throw new UnsupportedOperationException();
         }
     }

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/InternalMappedTerms.java

@@ -21,6 +21,7 @@ package org.elasticsearch.search.aggregations.bucket.terms;
 
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.search.DocValueFormat;
 import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
 
@@ -127,4 +128,9 @@ public abstract class InternalMappedTerms<A extends InternalTerms<A, B>, B exten
     protected int doHashCode() {
         return Objects.hash(super.doHashCode(), buckets, format, otherDocCount, showTermDocCountError, shardSize);
     }
+
+    @Override
+    public final XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
+        return doXContentCommon(builder, params, docCountError, otherDocCount, buckets);
+    }
 }

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/InternalTerms.java

@@ -21,6 +21,7 @@ package org.elasticsearch.search.aggregations.bucket.terms;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.search.DocValueFormat;
 import org.elasticsearch.search.aggregations.AggregationExecutionException;
 import org.elasticsearch.search.aggregations.Aggregations;
@@ -141,6 +142,21 @@ public abstract class InternalTerms<A extends InternalTerms<A, B>, B extends Int
             return newBucket(docCount, aggs, docCountError);
         }
 
+        @Override
+        public final XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+            builder.startObject();
+            keyToXContent(builder);
+            builder.field(CommonFields.DOC_COUNT, getDocCount());
+            if (showDocCountError) {
+                builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, getDocCountError());
+            }
+            aggregations.toXContentInternal(builder, params);
+            builder.endObject();
+            return builder;
+        }
+
+        protected abstract XContentBuilder keyToXContent(XContentBuilder builder) throws IOException;
+
         @Override
         public boolean equals(Object obj) {
             if (obj == null || getClass() != obj.getClass()) {
@@ -319,4 +335,16 @@ public abstract class InternalTerms<A extends InternalTerms<A, B>, B extends Int
     protected int doHashCode() {
         return Objects.hash(minDocCount, order, requiredSize);
     }
+
+    protected static XContentBuilder doXContentCommon(XContentBuilder builder, Params params,
+                                               long docCountError, long otherDocCount, List<? extends Bucket> buckets) throws IOException {
+        builder.field(DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, docCountError);
+        builder.field(SUM_OF_OTHER_DOC_COUNTS, otherDocCount);
+        builder.startArray(CommonFields.BUCKETS);
+        for (Bucket bucket : buckets) {
+            bucket.toXContent(builder, params);
+        }
+        builder.endArray();
+        return builder;
+    }
 }

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/LongTerms.java

@@ -86,18 +86,11 @@ public class LongTerms extends InternalMappedTerms<LongTerms, LongTerms.Bucket>
         }
 
         @Override
-        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-            builder.startObject();
+        protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
             builder.field(CommonFields.KEY, term);
             if (format != DocValueFormat.RAW) {
                 builder.field(CommonFields.KEY_AS_STRING, format.format(term));
             }
-            builder.field(CommonFields.DOC_COUNT, getDocCount());
-            if (showDocCountError) {
-                builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, getDocCountError());
-            }
-            aggregations.toXContentInternal(builder, params);
-            builder.endObject();
             return builder;
         }
 
@@ -149,18 +142,6 @@ public class LongTerms extends InternalMappedTerms<LongTerms, LongTerms.Bucket>
                 showTermDocCountError, otherDocCount, buckets, docCountError);
     }
 
-    @Override
-    public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, docCountError);
-        builder.field(SUM_OF_OTHER_DOC_COUNTS, otherDocCount);
-        builder.startArray(CommonFields.BUCKETS);
-        for (Bucket bucket : buckets) {
-            bucket.toXContent(builder, params);
-        }
-        builder.endArray();
-        return builder;
-    }
-
     @Override
     protected Bucket[] createBucketsArray(int size) {
         return new Bucket[size];

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/StringTerms.java

@@ -85,16 +85,8 @@ public class StringTerms extends InternalMappedTerms<StringTerms, StringTerms.Bu
         }
 
         @Override
-        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-            builder.startObject();
-            builder.field(CommonFields.KEY, getKeyAsString());
-            builder.field(CommonFields.DOC_COUNT, getDocCount());
-            if (showDocCountError) {
-                builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, getDocCountError());
-            }
-            aggregations.toXContentInternal(builder, params);
-            builder.endObject();
-            return builder;
+        protected final XContentBuilder keyToXContent(XContentBuilder builder) throws IOException {
+            return builder.field(CommonFields.KEY, getKeyAsString());
         }
 
         @Override
@@ -145,18 +137,6 @@ public class StringTerms extends InternalMappedTerms<StringTerms, StringTerms.Bu
                 showTermDocCountError, otherDocCount, buckets, docCountError);
     }
 
-    @Override
-    public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, docCountError);
-        builder.field(SUM_OF_OTHER_DOC_COUNTS, otherDocCount);
-        builder.startArray(CommonFields.BUCKETS);
-        for (Bucket bucket : buckets) {
-            bucket.toXContent(builder, params);
-        }
-        builder.endArray();
-        return builder;
-    }
-
     @Override
     protected Bucket[] createBucketsArray(int size) {
         return new Bucket[size];

core/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/UnmappedTerms.java

@@ -27,6 +27,7 @@ import org.elasticsearch.search.aggregations.InternalAggregations;
 import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -102,11 +103,8 @@ public class UnmappedTerms extends InternalTerms<UnmappedTerms, UnmappedTerms.Bu
     }
 
     @Override
-    public XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
-        builder.field(InternalTerms.DOC_COUNT_ERROR_UPPER_BOUND_FIELD_NAME, 0);
-        builder.field(SUM_OF_OTHER_DOC_COUNTS, 0);
-        builder.startArray(CommonFields.BUCKETS).endArray();
-        return builder;
+    public final XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
+        return doXContentCommon(builder, params, 0, 0, Collections.emptyList());
     }
 
     @Override