[Watcher] More robust handling of license at setup (#55831)

* Only register watcher app if we have received an indication of license first
Enable app to react to license updates from backend

* Return setup to a synchronous function.

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugins/watcher/__jest__/client_integration/helpers/app_context.mock.tsx

@@ -5,6 +5,7 @@
  */
 
 import React from 'react';
+import { of } from 'rxjs';
 import { ComponentType } from 'enzyme';
 import {
   chromeServiceMock,
@@ -15,6 +16,7 @@ import {
 } from '../../../../../../src/core/public/mocks';
 // eslint-disable-next-line @kbn/eslint/no-restricted-paths
 import { AppContextProvider } from '../../../public/application/app_context';
+import { LicenseStatus } from '../../../common/types/license_status';
 
 class MockTimeBuckets {
   setBounds(_domain: any) {
@@ -27,9 +29,7 @@ class MockTimeBuckets {
   }
 }
 export const mockContextValue = {
-  getLicenseStatus: () => ({
-    valid: true,
-  }),
+  licenseStatus$: of<LicenseStatus>({ valid: true }),
   docLinks: docLinksServiceMock.createStartContract(),
   chrome: chromeServiceMock.createStartContract(),
   MANAGEMENT_BREADCRUMB: { text: 'test' },

x-pack/plugins/watcher/public/application/app.tsx

@@ -4,7 +4,8 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
-import React from 'react';
+import React, { useEffect, useState } from 'react';
+import { Observable } from 'rxjs';
 import {
   ChromeStart,
   DocLinksStart,
@@ -47,12 +48,17 @@ export interface AppDeps {
   uiSettings: IUiSettingsClient;
   euiUtils: any;
   createTimeBuckets: () => any;
-  getLicenseStatus: () => LicenseStatus;
+  licenseStatus$: Observable<LicenseStatus>;
   MANAGEMENT_BREADCRUMB: any;
 }
 
 export const App = (deps: AppDeps) => {
-  const { valid, message } = deps.getLicenseStatus();
+  const [{ valid, message }, setLicenseStatus] = useState<LicenseStatus>({ valid: true });
+
+  useEffect(() => {
+    const s = deps.licenseStatus$.subscribe(setLicenseStatus);
+    return () => s.unsubscribe();
+  }, [deps.licenseStatus$]);
 
   if (!valid) {
     return (

x-pack/plugins/watcher/public/plugin.ts

@@ -5,80 +5,90 @@
  */
 import { i18n } from '@kbn/i18n';
 import { CoreSetup, Plugin, CoreStart } from 'kibana/public';
+import { first, map, skip } from 'rxjs/operators';
 
 import { FeatureCatalogueCategory } from '../../../../src/plugins/home/public';
 
 import { LicenseStatus } from '../common/types/license_status';
 
-import { LICENSE_CHECK_STATE } from '../../licensing/public';
+import { ILicense, LICENSE_CHECK_STATE } from '../../licensing/public';
 import { TimeBuckets, MANAGEMENT_BREADCRUMB } from './legacy';
 import { PLUGIN } from '../common/constants';
 import { Dependencies } from './types';
 
-export class WatcherUIPlugin implements Plugin<void, void, Dependencies, any> {
-  // Reference for when `mount` gets called, we don't want to render if
-  // we don't have a valid license. Under certain conditions the Watcher app link
-  // may still be present so this is a final guard.
-  private licenseStatus: LicenseStatus = { valid: false };
-  private hasRegisteredESManagementSection = false;
+const licenseToLicenseStatus = (license: ILicense): LicenseStatus => {
+  const { state, message } = license.check(PLUGIN.ID, PLUGIN.MINIMUM_LICENSE_REQUIRED);
+  return {
+    valid: state === LICENSE_CHECK_STATE.Valid && license.getFeature(PLUGIN.ID).isAvailable,
+    message,
+  };
+};
 
+export class WatcherUIPlugin implements Plugin<void, void, Dependencies, any> {
   setup(
     { application, notifications, http, uiSettings, getStartServices }: CoreSetup,
     { licensing, management, data, home }: Dependencies
   ) {
-    licensing.license$.subscribe(license => {
-      const { state, message } = license.check(PLUGIN.ID, PLUGIN.MINIMUM_LICENSE_REQUIRED);
-      this.licenseStatus = {
-        valid: state === LICENSE_CHECK_STATE.Valid && license.getFeature(PLUGIN.ID).isAvailable,
-        message,
-      };
-      if (this.licenseStatus.valid) {
-        const esSection = management.sections.getSection('elasticsearch');
-        if (esSection && !this.hasRegisteredESManagementSection) {
-          esSection.registerApp({
-            id: 'watcher',
-            title: i18n.translate(
-              'xpack.watcher.sections.watchList.managementSection.watcherDisplayName',
-              { defaultMessage: 'Watcher' }
-            ),
-            mount: async ({ element }) => {
-              const [core, plugins] = await getStartServices();
-              const { chrome, i18n: i18nDep, docLinks, savedObjects } = core;
-              const { eui_utils } = plugins as any;
-              const { boot } = await import('./application/boot');
+    const esSection = management.sections.getSection('elasticsearch');
 
-              return boot({
-                getLicenseStatus: () => this.licenseStatus,
-                element,
-                toasts: notifications.toasts,
-                http,
-                uiSettings,
-                docLinks,
-                chrome,
-                euiUtils: eui_utils,
-                savedObjects: savedObjects.client,
-                I18nContext: i18nDep.Context,
-                createTimeBuckets: () => new TimeBuckets(uiSettings, data),
-                MANAGEMENT_BREADCRUMB,
-              });
-            },
-          });
+    const watcherESApp = esSection!.registerApp({
+      id: 'watcher',
+      title: i18n.translate(
+        'xpack.watcher.sections.watchList.managementSection.watcherDisplayName',
+        { defaultMessage: 'Watcher' }
+      ),
+      mount: async ({ element }) => {
+        const [core, plugins] = await getStartServices();
+        const { chrome, i18n: i18nDep, docLinks, savedObjects } = core;
+        const { eui_utils } = plugins as any;
+        const { boot } = await import('./application/boot');
 
-          home.featureCatalogue.register({
-            id: 'watcher',
-            title: 'Watcher', // This is a product name so we don't translate it.
-            category: FeatureCatalogueCategory.ADMIN,
-            description: i18n.translate('xpack.watcher.watcherDescription', {
-              defaultMessage:
-                'Detect changes in your data by creating, managing, and monitoring alerts.',
-            }),
-            icon: 'watchesApp',
-            path: '/app/kibana#/management/elasticsearch/watcher/watches',
-            showOnHomePage: true,
-          });
+        return boot({
+          // Skip the first license status, because that's already been used to determine
+          // whether to include Watcher.
+          licenseStatus$: licensing.license$.pipe(skip(1), map(licenseToLicenseStatus)),
+          element,
+          toasts: notifications.toasts,
+          http,
+          uiSettings,
+          docLinks,
+          chrome,
+          euiUtils: eui_utils,
+          savedObjects: savedObjects.client,
+          I18nContext: i18nDep.Context,
+          createTimeBuckets: () => new TimeBuckets(uiSettings, data),
+          MANAGEMENT_BREADCRUMB,
+        });
+      },
+    });
 
-          this.hasRegisteredESManagementSection = true;
-        }
+    watcherESApp.disable();
+
+    // TODO: Fix the below dependency on `home` plugin inner workings
+    // Because the home feature catalogue does not have enable/disable functionality we pass
+    // the config in but keep a reference for enabling and disabling showing on home based on
+    // license updates.
+    const watcherHome = {
+      id: 'watcher',
+      title: 'Watcher', // This is a product name so we don't translate it.
+      category: FeatureCatalogueCategory.ADMIN,
+      description: i18n.translate('xpack.watcher.watcherDescription', {
+        defaultMessage: 'Detect changes in your data by creating, managing, and monitoring alerts.',
+      }),
+      icon: 'watchesApp',
+      path: '/app/kibana#/management/elasticsearch/watcher/watches',
+      showOnHomePage: true,
+    };
+
+    home.featureCatalogue.register(watcherHome);
+
+    licensing.license$.pipe(first(), map(licenseToLicenseStatus)).subscribe(({ valid }) => {
+      if (valid) {
+        watcherESApp.enable();
+        watcherHome.showOnHomePage = true;
+      } else {
+        watcherESApp.disable();
+        watcherHome.showOnHomePage = false;
       }
     });
   }