[data views] Automatic loading of field lists will no longer error on empty field list (#152059)

## Summary

Part of https://github.com/elastic/kibana/issues/151670
and follow up to https://github.com/elastic/kibana/pull/151788

When a data view is loaded, it automatically loads its field list.
Previously, it would error if the index pattern failed to match an
index. Going forward, this will be treated as a valid empty state -
`allowNoIndices` is being passed to the field_caps requests. When
`allowNoIndices` is set to true, ES will return a valid empty set rather
than a 404 error.


### 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: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

src/plugins/data_views/common/data_views/data_views.test.ts

@@ -164,6 +164,19 @@ describe('IndexPatterns', () => {
     expect(apiClient.getFieldsForWildcard).toBeCalledTimes(2);
   });
 
+  test('getFieldsForWildcard called with allowNoIndex set to true as default ', async () => {
+    const id = '1';
+    await indexPatterns.get(id);
+    expect(apiClient.getFieldsForWildcard).toBeCalledWith({
+      allowNoIndex: true,
+      indexFilter: undefined,
+      metaFields: false,
+      pattern: 'something',
+      rollupIndex: undefined,
+      type: undefined,
+    });
+  });
+
   test('does cache ad-hoc data views', async () => {
     const id = '1';
 
@@ -608,9 +621,8 @@ describe('IndexPatterns', () => {
       expect(indexPattern.fields.length).toBe(1);
     });
 
-    test('refreshFields properly includes allowNoIndex', async () => {
+    test('refreshFields defaults allowNoIndex to true', async () => {
       const indexPatternSpec: DataViewSpec = {
-        allowNoIndex: true,
         title: 'test',
       };
 

src/plugins/data_views/common/data_views/data_views.ts

@@ -515,12 +515,12 @@ export class DataViewsService {
    */
   getFieldsForIndexPattern = async (
     indexPattern: DataView | DataViewSpec,
-    options?: GetFieldsOptions
+    options?: Omit<GetFieldsOptions, 'allowNoIndex'>
   ) =>
     this.getFieldsForWildcard({
       type: indexPattern.type,
       rollupIndex: indexPattern?.typeMeta?.params?.rollup_index,
-      allowNoIndex: indexPattern.allowNoIndex,
+      allowNoIndex: true,
       ...options,
       pattern: indexPattern.title as string,
     });
@@ -530,7 +530,7 @@ export class DataViewsService {
     return this.apiClient.getFieldsForWildcard({
       type: dataView.type,
       rollupIndex: dataView?.typeMeta?.params?.rollup_index,
-      allowNoIndex: dataView.allowNoIndex,
+      allowNoIndex: true,
       pattern: dataView.getIndexPattern(),
       metaFields,
     });
@@ -538,12 +538,12 @@ export class DataViewsService {
 
   private getFieldsAndIndicesForWildcard = async (options: GetFieldsOptions) => {
     const metaFields = await this.config.get<string[]>(META_FIELDS);
-    return await this.apiClient.getFieldsForWildcard({
+    return this.apiClient.getFieldsForWildcard({
       pattern: options.pattern,
       metaFields,
       type: options.type,
       rollupIndex: options.rollupIndex,
-      allowNoIndex: options.allowNoIndex,
+      allowNoIndex: true,
       indexFilter: options.indexFilter,
     });
   };

src/plugins/data_views/server/fetcher/lib/field_capabilities/field_capabilities.ts

@@ -50,12 +50,13 @@ export async function getFieldCapabilities(params: FieldCapabilitiesParams) {
     indexFilter,
     fields,
   });
-  const fieldsFromFieldCapsByName = keyBy(readFieldCapsResponse(esFieldCaps.body), 'name');
+  const fieldCapsArr = readFieldCapsResponse(esFieldCaps.body);
+  const fieldsFromFieldCapsByName = keyBy(fieldCapsArr, 'name');
 
   const allFieldsUnsorted = Object.keys(fieldsFromFieldCapsByName)
     // not all meta fields are provided, so remove and manually add
     .filter((name) => !fieldsFromFieldCapsByName[name].metadata_field)
-    .concat(metaFields)
+    .concat(fieldCapsArr.length ? metaFields : [])
     .reduce<{ names: string[]; map: Map<string, string> }>(
       (agg, value) => {
         // This is intentionally using a Map to be highly optimized with very large indexes AND be safe for user provided data

test/functional/apps/discover/group3/_sidebar.ts

@@ -426,9 +426,9 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
         await PageObjects.discover.waitUntilSidebarHasLoaded();
 
         expect(await PageObjects.discover.getSidebarAriaDescription()).to.be(
-          '0 available fields. 0 meta fields.'
+          '0 available fields. 0 empty fields. 0 meta fields.'
         );
-        await testSubjects.existOrFail(
+        await testSubjects.missingOrFail(
           `${PageObjects.discover.getSidebarSectionSelector('available')}-fetchWarning`
         );
         await testSubjects.existOrFail(