[Discover/CSV Reporting] Fix support for nested field columns in CSV …

…reports (elastic#172240)

## Summary

When we generate the parameters for the report, we add all of the
selected columns as entries in the search request `fields` array (or `*`
if none are selected, which is why this case works), but this doesn't
work for nested fields since [the fields API doesn't support nested
field
roots](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-fields.html#search-fields-nested):
>However, when the `fields` pattern targets the nested `user` field
directly, no values will be returned because the pattern doesn’t match
any leaf fields.

Instead we can detect nested fields and add them to the `fields` array
as `{nestedFieldName}.*`, ensuring that all of the leaf fields are
returned in the response.

Fixes elastic#172236.

### Checklist

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] Any UI touched in this PR is usable by keyboard only (learn more
about [keyboard accessibility](https://webaim.org/techniques/keyboard/))
- [ ] Any UI touched in this PR does not create any new axe failures
(run axe in browser:
[FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/),
[Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
- [ ] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)

### For maintainers

- [ ] This was checked for breaking API changes and was [labeled
appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

---------

Co-authored-by: kibanamachine <[email protected]>
(cherry picked from commit ab5ff9c)

# Conflicts:
#	src/plugins/discover/public/application/apps/main/utils/get_sharing_data.test.ts
#	src/plugins/discover/public/application/apps/main/utils/get_sharing_data.ts
#	x-pack/plugins/reporting/tsconfig.json

src/plugins/discover/public/application/apps/main/utils/get_sharing_data.test.ts

@@ -17,6 +17,7 @@ import {
   SEARCH_FIELDS_FROM_SOURCE,
 } from '../../../../../common';
 import { indexPatternMock } from '../../../../__mocks__/index_pattern';
+import { buildDataViewMock, dataViewMock } from '@kbn/discover-utils/src/__mocks__';
 import { getSharingData, showPublicUrlSwitch } from './get_sharing_data';
 
 describe('getSharingData', () => {
@@ -147,6 +148,38 @@ describe('getSharingData', () => {
     );
     expect(getSearchSource().fields).toStrictEqual([
       'cool-timefield',
+    ]);
+  });
+
+  test('getSearchSource supports nested fields', async () => {
+    const index = buildDataViewMock({
+      name: 'the-data-view',
+      timeFieldName: 'cool-timefield',
+      fields: [
+        ...dataViewMock.fields,
+        {
+          name: 'cool-field-2.field',
+          type: 'keyword',
+          subType: {
+            nested: {
+              path: 'cool-field-2.field.path',
+            },
+          },
+        },
+      ] as DataView['fields'],
+    });
+    const searchSourceMock = createSearchSourceMock({ index });
+    const { getSearchSource } = await getSharingData(
+      searchSourceMock,
+      {
+        columns: ['cool-field-1', 'cool-field-2'],
+      },
+      services
+    );
+    expect(getSearchSource({}).fields).toStrictEqual([
+      { field: 'cool-timefield', include_unmapped: 'true' },
+      { field: 'cool-field-1', include_unmapped: 'true' },
+      { field: 'cool-field-2.*', include_unmapped: 'true' },
       'cool-field-1',
       'cool-field-2',
       'cool-field-3',

src/plugins/discover/public/application/apps/main/utils/get_sharing_data.ts

@@ -12,6 +12,7 @@ import type { DataPublicPluginStart } from 'src/plugins/data/public';
 import type { Filter, ISearchSource, SearchSourceFields } from 'src/plugins/data/common';
 import {
   DOC_HIDE_TIME_COLUMN_SETTING,
+  isNestedFieldParent,
   SORT_DEFAULT_ORDER_SETTING,
   SEARCH_FIELDS_FROM_SOURCE,
 } from '../../../../../common';
@@ -93,6 +94,21 @@ export async function getSharingData(
       const useFieldsApi = !config.get(SEARCH_FIELDS_FROM_SOURCE);
       if (useFieldsApi && columns.length) {
         searchSource.setField('fields', columns);
+      const useFieldsApi = !uiSettings.get(SEARCH_FIELDS_FROM_SOURCE);
+      if (useFieldsApi) {
+        searchSource.removeField('fieldsFromSource');
+        const fields = columns.length
+          ? columns.map((column) => {
+              let field = column;
+
+              // If this column is a nested field, add a wildcard to the field name in order to fetch
+              // all leaf fields for the report, since the fields API doesn't support nested field roots
+              if (isNestedFieldParent(column, index)) {
+                field = `${column}.*`;
+              }
+
+              return { field, include_unmapped: 'true' };
+            })
       }
       return searchSource.getSerializedFields(true);
     },

x-pack/plugins/reporting/public/panel_actions/get_csv_panel_action.test.ts

@@ -17,6 +17,7 @@ import { ReportingAPIClient } from '../lib/reporting_api_client';
 import type { ReportingPublicPluginStartDendencies } from '../plugin';
 import type { ActionContext } from './get_csv_panel_action';
 import { ReportingCsvPanelAction } from './get_csv_panel_action';
+import { dataViewMock } from '@kbn/discover-utils/src/__mocks__';
 
 type LicenseResults = 'valid' | 'invalid' | 'unavailable' | 'expired';
 
@@ -119,7 +120,7 @@ describe('GetCsvReportPanelAction', () => {
       createCopy: () => mockSearchSource,
       removeField: jest.fn(),
       setField: jest.fn(),
-      getField: jest.fn(),
+      getField: jest.fn((name) => (name === 'index' ? dataViewMock : undefined)),
       getSerializedFields: jest.fn().mockImplementation(() => ({ testData: 'testDataValue' })),
     } as unknown as SearchSource;
     context.embeddable.getSavedSearch = () => {

x-pack/plugins/reporting/tsconfig.json

@@ -11,6 +11,7 @@
     "public/**/*",
     "server/**/*",
     "../../../typings/**/*"
+    "@kbn/discover-utils",
   ],
   "references": [
     { "path": "../../../src/core/tsconfig.json" },