[Discover] Fix loading data views in ES|QL mode (elastic#199099)

- Closes elastic#199065

## Summary

This PR makes sure that data views are loaded so user can view them
after switching from ES|QL mode to data view mode.

Looks like it was introduced in
elastic#195670

### Testing

On your local instance having `kibana_sample_data_logs` installed

* Open a link to an ES|QL query
[link](http://localhost:5601/xot/app/discover#/?_g=(filters:!(),refreshInterval:(pause:!t,value:60000),time:(from:now-15m,to:now))&_a=(columns:!(),dataSource:(dataViewId:e3465e67bdeced2befff9f9dca7ecf9c48504cad68a10efd881f4c7dd5ade28a,type:dataView),filters:!(),interval:auto,query:(language:kuery,query:''),sort:!(!(timestamp,desc))))
* Switch to classic
* Open the DataView Picker, to see a list of DataViews, before this fix
there were none

### Checklist

- [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

---------

Co-authored-by: Julia Rechkunova <[email protected]>
Co-authored-by: Julia Rechkunova <[email protected]>
(cherry picked from commit 08b83c5)

src/plugins/discover/public/application/main/discover_main_route.tsx

@@ -120,14 +120,10 @@ export function DiscoverMainRoute({
         const { dataSource } = stateContainer.appState.getState();
         const isEsqlQuery = isDataSourceType(dataSource, DataSourceType.Esql);
 
-        // ES|QL should work without data views
-        // Given we have a saved search id, we can skip the data/data view check, too
-        // A given nextDataView is provided by the user, and therefore we can skip the data/data view check
-
         if (savedSearchId || isEsqlQuery || nextDataView) {
-          if (!isEsqlQuery) {
-            await stateContainer.actions.loadDataViewList();
-          }
+          // Although ES|QL doesn't need a data view, we still need to load the data view list to
+          // ensure the data view is available for the user to switch to classic mode
+          await stateContainer.actions.loadDataViewList();
           return true;
         }
 

test/functional/apps/discover/esql/_esql_view.ts

@@ -25,14 +25,17 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
   const find = getService('find');
   const esql = getService('esql');
   const dashboardAddPanel = getService('dashboardAddPanel');
-  const { common, discover, dashboard, header, timePicker, unifiedFieldList } = getPageObjects([
-    'common',
-    'discover',
-    'dashboard',
-    'header',
-    'timePicker',
-    'unifiedFieldList',
-  ]);
+  const dataViews = getService('dataViews');
+  const { common, discover, dashboard, header, timePicker, unifiedFieldList, unifiedSearch } =
+    getPageObjects([
+      'common',
+      'discover',
+      'dashboard',
+      'header',
+      'timePicker',
+      'unifiedFieldList',
+      'unifiedSearch',
+    ]);
 
   const defaultSettings = {
     defaultIndex: 'logstash-*',
@@ -305,6 +308,24 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
           await testSubjects.existOrFail('discover-esql-to-dataview-modal');
         });
       });
+
+      it('should show available data views after switching to classic mode', async () => {
+        await discover.selectTextBaseLang();
+        await header.waitUntilLoadingHasFinished();
+        await discover.waitUntilSearchingHasFinished();
+
+        await browser.refresh();
+        await header.waitUntilLoadingHasFinished();
+        await discover.waitUntilSearchingHasFinished();
+        await unifiedSearch.switchToDataViewMode();
+        await header.waitUntilLoadingHasFinished();
+        await discover.waitUntilSearchingHasFinished();
+        const availableDataViews = await unifiedSearch.getDataViewList(
+          'discover-dataView-switch-link'
+        );
+        expect(availableDataViews).to.eql(['kibana_sample_data_flights', 'logstash-*']);
+        await dataViews.switchToAndValidate('kibana_sample_data_flights');
+      });
     });
 
     describe('inspector', () => {

test/functional/page_objects/unified_search_page.ts

@@ -27,6 +27,28 @@ export class UnifiedSearchPageObject extends FtrService {
     );
   }
 
+  public async getDataViewList(switchButtonSelector: string) {
+    await this.testSubjects.click(switchButtonSelector);
+
+    await this.retry.waitFor(
+      'wait for popover',
+      async () => await this.testSubjects.exists('indexPattern-switcher')
+    );
+
+    const indexPatternSwitcher = await this.testSubjects.find('indexPattern-switcher', 500);
+    const availableDataViews = await Promise.all(
+      (
+        await indexPatternSwitcher.findAllByCssSelector('.euiSelectableListItem')
+      ).map(async (item) => {
+        return await item.getAttribute('title');
+      })
+    );
+
+    await this.testSubjects.click(switchButtonSelector);
+
+    return availableDataViews;
+  }
+
   public async getSelectedDataView(switchButtonSelector: string) {
     let visibleText = '';
 
@@ -46,6 +68,12 @@ export class UnifiedSearchPageObject extends FtrService {
 
   public async switchToDataViewMode() {
     await this.testSubjects.click('switch-to-dataviews');
+    await this.retry.waitFor('the modal to open', async () => {
+      return await this.testSubjects.exists('discover-esql-to-dataview-modal');
+    });
     await this.testSubjects.click('discover-esql-to-dataview-no-save-btn');
+    await this.retry.waitFor('the modal to close', async () => {
+      return !(await this.testSubjects.exists('discover-esql-to-dataview-modal'));
+    });
   }
 }

x-pack/test_serverless/functional/test_suites/common/discover/esql/_esql_view.ts

@@ -21,6 +21,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
   const find = getService('find');
   const esql = getService('esql');
   const dashboardAddPanel = getService('dashboardAddPanel');
+  const dataViews = getService('dataViews');
   const PageObjects = getPageObjects([
     'svlCommonPage',
     'common',
@@ -29,6 +30,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
     'header',
     'timePicker',
     'unifiedFieldList',
+    'unifiedSearch',
   ]);
 
   const defaultSettings = {
@@ -311,6 +313,24 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
           await testSubjects.existOrFail('discover-esql-to-dataview-modal');
         });
       });
+
+      it('should show available data views after switching to classic mode', async () => {
+        await PageObjects.discover.selectTextBaseLang();
+        await PageObjects.header.waitUntilLoadingHasFinished();
+        await PageObjects.discover.waitUntilSearchingHasFinished();
+
+        await browser.refresh();
+        await PageObjects.header.waitUntilLoadingHasFinished();
+        await PageObjects.discover.waitUntilSearchingHasFinished();
+        await PageObjects.unifiedSearch.switchToDataViewMode();
+        await PageObjects.header.waitUntilLoadingHasFinished();
+        await PageObjects.discover.waitUntilSearchingHasFinished();
+        const availableDataViews = await PageObjects.unifiedSearch.getDataViewList(
+          'discover-dataView-switch-link'
+        );
+        expect(availableDataViews).to.eql(['kibana_sample_data_flights', 'logstash-*']);
+        await dataViews.switchToAndValidate('kibana_sample_data_flights');
+      });
     });
 
     describe('inspector', () => {