Update AggConfig for nested sibling pipeline aggs (elastic#140650)

src/plugins/data/common/search/aggs/agg_config.test.ts

@@ -191,6 +191,85 @@ describe('AggConfig', () => {
       expect(dsl.aggs[medianConfig.id]).toHaveProperty('percentiles');
       expect(dsl.aggs[medianConfig.id].percentiles).toBe(football);
     });
+
+    it('properly handles nested sibling pipeline aggregations', () => {
+      const customBucket = {
+        type: 'date_histogram',
+        params: {
+          field: '@timestamp',
+          interval: '1h',
+        },
+      };
+      const customMetric = {
+        type: 'avg_bucket',
+        params: {
+          customBucket: {
+            type: 'date_histogram',
+            params: {
+              field: '@timestamp',
+              interval: '30m',
+            },
+          },
+          customMetric: {
+            type: 'sum',
+            params: {
+              field: 'bytes',
+            },
+          },
+        },
+      };
+      const configStates = [
+        {
+          type: 'avg_bucket',
+          params: {
+            customBucket,
+            customMetric,
+          },
+        },
+      ];
+      const ac = new AggConfigs(indexPattern, configStates, { typesRegistry }, jest.fn());
+      const dsl = ac.toDsl();
+
+      expect(dsl).toMatchInlineSnapshot(`
+        Object {
+          "1": Object {
+            "avg_bucket": Object {
+              "buckets_path": "1-bucket>1-metric",
+            },
+          },
+          "1-bucket": Object {
+            "aggs": Object {
+              "1-bucket": Object {
+                "aggs": Object {
+                  "1-metric": Object {
+                    "sum": Object {
+                      "field": "bytes",
+                    },
+                  },
+                },
+                "date_histogram": Object {
+                  "field": "@timestamp",
+                  "fixed_interval": "30m",
+                  "min_doc_count": 1,
+                  "time_zone": "dateFormat:tz",
+                },
+              },
+              "1-metric": Object {
+                "avg_bucket": Object {
+                  "buckets_path": "1-bucket>1-metric",
+                },
+              },
+            },
+            "date_histogram": Object {
+              "calendar_interval": "1h",
+              "field": "@timestamp",
+              "min_doc_count": 1,
+              "time_zone": "dateFormat:tz",
+            },
+          },
+        }
+      `);
+    });
   });
 
   describe('::ensureIds', () => {

src/plugins/data/common/search/aggs/metrics/lib/sibling_pipeline_agg_writer.ts

@@ -6,21 +6,25 @@
  * Side Public License, v 1.
  */
 
+import { siblingPipelineType } from '../../../..';
 import { IMetricAggConfig } from '../metric_agg_type';
 import { METRIC_TYPES } from '../metric_agg_types';
 
 export const siblingPipelineAggWriter = (agg: IMetricAggConfig, output: Record<string, any>) => {
-  const customMetric = agg.getParam('customMetric');
-
-  if (!customMetric) return;
-
-  const metricAgg = customMetric;
+  const metricAgg = agg.getParam('customMetric');
   const bucketAgg = agg.getParam('customBucket');
+  if (!metricAgg) return;
 
   // if a bucket is selected, we must add this agg as a sibling to it, and add a metric to that bucket (or select one of its)
   if (metricAgg.type.name !== METRIC_TYPES.COUNT) {
     bucketAgg.subAggs = (output.subAggs || []).concat(metricAgg);
     output.params.buckets_path = `${bucketAgg.id}>${metricAgg.id}`;
+
+    // If the metric is another nested sibling pipeline agg, we need to include it as a sub-agg of this agg's bucket agg
+    if (metricAgg.type.subtype === siblingPipelineType) {
+      const subAgg = metricAgg.getParam('customBucket');
+      if (subAgg) bucketAgg.subAggs.push(subAgg);
+    }
   } else {
     output.params.buckets_path = bucketAgg.id + '>_count';
   }