[Tabify] Add meta option to include top-level underscored field values (#90535)

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

Author: tsullivan

src/plugins/data/common/search/tabify/__snapshots__/tabify_docs.test.ts.snap

@@ -37,6 +37,10 @@ describe('tabifyDocs', () => {
     hits: {
       hits: [
         {
+          _id: 'hit-id-value',
+          _index: 'hit-index-value',
+          _type: 'hit-type-value',
+          _score: 77,
           _source: { sourceTest: 123 },
           fields: { fieldTest: 123, invalidMapping: 345, nested: [{ field: 123 }] },
         },
@@ -59,6 +63,11 @@ describe('tabifyDocs', () => {
     expect(table).toMatchSnapshot();
   });
 
+  it('combines meta fields if meta option is set', () => {
+    const table = tabifyDocs(response, index, { meta: true });
+    expect(table).toMatchSnapshot();
+  });
+
   it('works without provided index pattern', () => {
     const table = tabifyDocs(response);
     expect(table).toMatchSnapshot();

src/plugins/data/common/search/tabify/tabify_docs.test.ts

@@ -11,6 +11,12 @@ import { isPlainObject } from 'lodash';
 import { IndexPattern } from '../../index_patterns/index_patterns';
 import { Datatable, DatatableColumn, DatatableColumnType } from '../../../../expressions/common';
 
+export interface TabifyDocsOptions {
+  shallow?: boolean;
+  source?: boolean;
+  meta?: boolean;
+}
+
 export function flattenHit(
   hit: SearchResponse<unknown>['hits']['hits'][0],
   indexPattern?: IndexPattern,
@@ -56,12 +62,13 @@ export function flattenHit(
   if (params?.source !== false && hit._source) {
     flatten(hit._source as Record<string, any>);
   }
-  return flat;
-}
+  if (params?.meta !== false) {
+    // combine the fields that Discover allows to add as columns
+    const { _id, _index, _type, _score } = hit;
+    flatten({ _id, _index, _score, _type });
+  }
 
-export interface TabifyDocsOptions {
-  shallow?: boolean;
-  source?: boolean;
+  return flat;
 }
 
 export const tabifyDocs = (