[APM] Fix missing apm indicies (elastic#53541)

* [APM] Fix missing apm indicies

* Fix infinite loop in ui indices

* Add test for empty settings

x-pack/legacy/plugins/apm/public/components/app/Settings/ApmIndices/index.test.tsx

@@ -0,0 +1,35 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { render, wait } from '@testing-library/react';
+import React from 'react';
+import { ApmIndices } from '.';
+import { MockApmPluginContextWrapper } from '../../../../utils/testHelpers';
+import * as hooks from '../../../../hooks/useFetcher';
+
+describe('ApmIndices', () => {
+  it('should not get stuck in infinite loop', async () => {
+    spyOn(hooks, 'useFetcher').and.returnValue({
+      data: undefined,
+      status: 'loading'
+    });
+    const { getByText } = render(
+      <MockApmPluginContextWrapper>
+        <ApmIndices />
+      </MockApmPluginContextWrapper>
+    );
+
+    expect(getByText('Indices')).toMatchInlineSnapshot(`
+      <h2
+        class="euiTitle euiTitle--medium"
+      >
+        Indices
+      </h2>
+    `);
+
+    await wait();
+  });
+});

x-pack/legacy/plugins/apm/public/components/app/Settings/ApmIndices/index.tsx

@@ -85,6 +85,9 @@ async function saveApmIndices({
   clearCache();
 }
 
+// avoid infinite loop by initializing the state outside the component
+const INITIAL_STATE = [] as [];
+
 export function ApmIndices() {
   const { toasts } = useApmPluginContext().core.notifications;
 
@@ -93,7 +96,7 @@ export function ApmIndices() {
 
   const callApmApiFromHook = useCallApmApi();
 
-  const { data = [], status, refetch } = useFetcher(
+  const { data = INITIAL_STATE, status, refetch } = useFetcher(
     callApmApi =>
       callApmApi({ pathname: `/api/apm/settings/apm-index-settings` }),
     []

x-pack/legacy/plugins/apm/server/lib/settings/apm_indices/save_apm_indices.test.ts

@@ -0,0 +1,37 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { saveApmIndices } from './save_apm_indices';
+
+describe('saveApmIndices', () => {
+  it('should trim and strip empty settings', async () => {
+    const context = {
+      core: {
+        savedObjects: {
+          client: {
+            create: jest.fn()
+          }
+        }
+      }
+    } as any;
+
+    const apmIndices = {
+      settingA: 'aa',
+      settingB: '',
+      settingC: undefined,
+      settingD: null,
+      settingE: ' ',
+      settingF: 'ff',
+      settingG: ' gg '
+    } as any;
+    await saveApmIndices(context, apmIndices);
+    expect(context.core.savedObjects.client.create).toHaveBeenCalledWith(
+      expect.any(String),
+      { settingA: 'aa', settingF: 'ff', settingG: 'gg' },
+      expect.any(Object)
+    );
+  });
+});

x-pack/legacy/plugins/apm/server/lib/settings/apm_indices/save_apm_indices.ts

@@ -13,14 +13,23 @@ import { APMRequestHandlerContext } from '../../../routes/typings';
 
 export async function saveApmIndices(
   context: APMRequestHandlerContext,
-  apmIndicesSavedObject: Partial<ApmIndicesConfig>
+  apmIndices: Partial<ApmIndicesConfig>
 ) {
   return await context.core.savedObjects.client.create(
     APM_INDICES_SAVED_OBJECT_TYPE,
-    apmIndicesSavedObject,
+    removeEmpty(apmIndices),
     {
       id: APM_INDICES_SAVED_OBJECT_ID,
       overwrite: true
     }
   );
 }
+
+// remove empty/undefined values
+function removeEmpty(apmIndices: Partial<ApmIndicesConfig>) {
+  return Object.fromEntries(
+    Object.entries(apmIndices)
+      .map(([key, value]) => [key, value?.trim()])
+      .filter(([key, value]) => !!value)
+  );
+}