Merge "Introduce AppContext"

Author: milutin

polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js

@@ -30,7 +30,7 @@ import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-l
 import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
 import {PolymerElement} from '@polymer/polymer/polymer-element.js';
 import {htmlTemplate} from './gr-change-list_html.js';
-import {flags} from '../../../services/flags';
+import {appContext} from '../../../services/app-context.js';
 import {BaseUrlBehavior} from '../../../behaviors/base-url-behavior/base-url-behavior.js';
 import {ChangeTableBehavior} from '../../../behaviors/gr-change-table-behavior/gr-change-table-behavior.js';
 import {URLEncodingBehavior} from '../../../behaviors/gr-url-encoding-behavior/gr-url-encoding-behavior.js';
@@ -152,6 +152,11 @@ class GrChangeList extends mixinBehaviors( [
     };
   }
 
+  constructor() {
+    super();
+    this.flagsService = appContext.flagsService;
+  }
+
   /** @override */
   created() {
     super.created();
@@ -204,7 +209,7 @@ class GrChangeList extends mixinBehaviors( [
     this.changeTableColumns = this.columnNames;
     this.showNumber = false;
     this.visibleChangeTableColumns = this.getEnabledColumns(this.columnNames,
-        config, flags.enabledExperiments);
+        config, this.flagsService.enabledExperiments);
 
     if (account) {
       this.showNumber = !!(preferences &&
@@ -213,7 +218,7 @@ class GrChangeList extends mixinBehaviors( [
           preferences.change_table.length > 0) {
         const prefColumns = this.getVisibleColumns(preferences.change_table);
         this.visibleChangeTableColumns = this.getEnabledColumns(prefColumns,
-            config, flags.enabledExperiments);
+            config, this.flagsService.enabledExperiments);
       }
     }
   }

polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js

@@ -17,7 +17,7 @@
 import '../../../scripts/bundled-polymer.js';
 
 import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
-import {flags} from '../../../services/flags';
+import {appContext} from '../../../services/app-context.js';
 
 // Latency reporting constants.
 const TIMING = {
@@ -279,7 +279,7 @@ let GrReporting = Polymer({
       eventInfo.inBackgroundTab = isInBackgroundTab;
     }
 
-    const enabledExperiments = flags.enabledExperiments;
+    const enabledExperiments = appContext.flagsService.enabledExperiments;
     if (enabledExperiments.length) {
       eventInfo.enabledExperiments = JSON.stringify(enabledExperiments);
     }

polygerrit-ui/app/elements/gr-app-init.js

@@ -14,11 +14,14 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+import {initAppContext} from '../services/app-context-init.js';
 
 if (!window.Polymer) {
   window.Polymer = {
     passiveTouchGestures: true,
     lazyRegister: true,
   };
 }
-window.Gerrit = window.Gerrit || {};
+window.Gerrit = window.Gerrit || {};
+
+initAppContext();

polygerrit-ui/app/services/README.md

@@ -9,10 +9,34 @@ Services should be stateful, if its just pure functions, consider having them in
 Regarding all stateful should be considered as services or not, it's still TBD. Will update as soon
 as it's finalized.
 
-## Future plans
+## How to access service
 
-To make services much easier to use, we may need to adopt a DI (dependency injection) system instead of exporting singleton
-from the services directly. And it will help in mocking services in tests as well.
+We use AppContext to access instance of service. It helps in mocking service in tests as well.
+We prefer setting instance of service in constructor and then accessing it from variable. We also
+allow access straight from appContext especially in static methods.
+
+```
+import {appContext} from '../../../services/app-context.js';
+
+class T {
+  constructor() {
+    super();
+    this.flagsService = appContext.flagsService;
+  }
+
+  action1() {
+    if (this.flagsService.isEnabled('test)) {
+      // do something
+    }
+  }
+}
+
+staticMethod() {
+  if (appContext.flagsService.isEnabled('test)) {
+    // do something
+  }
+}
+```
 
 ## What services we have
 
@@ -21,10 +45,10 @@ from the services directly. And it will help in mocking services in tests as wel
 'flags' is a service to provide easy access to all enabled experiments.
 
 ```
-import {flags} from "./flags.js";
+import {appContext} from '../../../services/app-context.js';
 
 // check if an experiment is enabled or not
-if (flags.isEnabled('test')) {
+if (appContext.flagsService.isEnabled('test')) {
   // do something
 }
 ```

polygerrit-ui/app/services/app-context-init.js

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {appContext} from './app-context.js';
+import {FlagsService} from './flags.js';
+
+const initializedServices = new Map();
+
+function getService(serviceName, serviceInit) {
+  if (!initializedServices[serviceName]) {
+    initializedServices[serviceName] = serviceInit();
+  }
+  return initializedServices[serviceName];
+}
+
+/**
+ * The AppContext lazy initializator for all services
+ */
+export function initAppContext() {
+  const registeredServices = {};
+  function addService(serviceName, serviceCreator) {
+    if (registeredServices[serviceName]) {
+      throw new Error(`Service ${serviceName} already registered.`);
+    }
+    registeredServices[serviceName] = {
+      get() {
+        return getService(serviceName, serviceCreator);
+      },
+    };
+  }
+
+  addService('flagsService', () => new FlagsService());
+
+  Object.defineProperties(appContext, registeredServices);
+}

polygerrit-ui/app/services/app-context-init_test.html

@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<!--
+@license
+Copyright (C) 2020 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
+<script src="/node_modules/@webcomponents/webcomponentsjs/custom-elements-es5-adapter.js"></script>
+<script src="/node_modules/@webcomponents/webcomponentsjs/webcomponents-lite.js"></script>
+<script src="/components/wct-browser-legacy/browser.js"></script>
+
+<script type="module">
+  import '../test/common-test-setup.js';
+  import {appContext} from './app-context.js';
+  import {initAppContext} from './app-context-init.js';
+  suite('app context initializer tests', () => {
+    setup(() => {
+      initAppContext();
+    });
+
+    test('all services initialized and are singletons', () => {
+      Object.keys(appContext).forEach(serviceName => {
+        const service = appContext[serviceName];
+        assert.isNotNull(service);
+        const service2 = appContext[serviceName];
+        assert.strictEqual(service, service2);
+      });
+    });
+  });
+</script>

polygerrit-ui/app/services/app-context.js

@@ -0,0 +1,26 @@
+/**
+ * @license
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * The AppContext holds immortal singleton instances of services. It's a
+ * convenient way to provide singletons that can be swapped out for testing.
+ *
+ * AppContext is initialized in ./app-context-init.js
+ */
+export const appContext = {
+  flagsService: null,
+};

polygerrit-ui/app/services/flags.js

@@ -20,7 +20,7 @@
  *
  * Provides all related methods / properties regarding on feature flags.
  */
-class Flags {
+export class FlagsService {
   constructor() {
     // stores all enabled experiments
     this._experiments = new Set();
@@ -46,6 +46,3 @@ class Flags {
     return [...this._experiments];
   }
 }
-
-// Export a single instance of Flags to be used across components.
-export const flags = new Flags();

polygerrit-ui/app/services/flags_test.html

@@ -27,12 +27,9 @@
 
 <script type="module">
   import '../test/common-test-setup.js';
-  import {flags} from './flags.js';
-  import {flags as flags2} from './flags.js';
+  import {FlagsService} from './flags.js';
   suite('flags tests', () => {
-    test('singlton', () => {
-      assert.equal(flags, flags2);
-    });
+    const flags = new FlagsService();
 
     test('isEnabled', () => {
       assert.equal(flags.isEnabled('a'), true);

polygerrit-ui/app/test/common-test-setup.js

@@ -21,7 +21,7 @@ import '@polymer/iron-test-helpers/iron-test-helpers.js';
 import './test-router.js';
 import moment from 'moment/src/moment.js';
 import {SafeTypes} from '../behaviors/safe-types-behavior/safe-types-behavior.js';
-
+import {initAppContext} from '../services/app-context-init.js';
 self.moment = moment;
 security.polymer_resin.install({
   allowedIdentifierPrefixes: [''],
@@ -78,6 +78,7 @@ setup(() => {
   if (Gerrit._testOnly_resetPlugins) {
     Gerrit._testOnly_resetPlugins();
   }
+  initAppContext();
 });
 
 if (window.stub) {