feat(PromisePipe): add pipe for promises

modules/angular2/src/change_detection/pipes/promise_pipe.ts

@@ -0,0 +1,95 @@
+import {Promise, PromiseWrapper} from 'angular2/src/facade/async';
+import {isBlank, isPresent} from 'angular2/src/facade/lang';
+import {Pipe, WrappedValue} from './pipe';
+import {ChangeDetectorRef} from '../change_detector_ref';
+
+// HACK: workaround for Traceur behavior.
+// It expects all transpiled modules to contain this marker.
+// TODO: remove this when we no longer use traceur
+export var __esModule = true;
+
+/**
+ * Implements async bindings to Promise.
+ *
+ * # Example
+ *
+ * In this example we bind the description promise to the DOM.
+ * The async pipe will convert a promise to the value with which it is resolved. It will also
+ * request a change detection check when the promise is resolved.
+ *
+ *  ```
+ * @Component({
+ *   selector: "task-cmp",
+ *   changeDetection: ON_PUSH
+ * })
+ * @View({
+ *  inline: "Task Description {{description|promise}}"
+ * })
+ * class Task {
+ *  description:Promise<string>;
+ * }
+ *
+ * ```
+ *
+ * @exportedAs angular2/pipes
+ */
+export class PromisePipe extends Pipe {
+  _ref: ChangeDetectorRef;
+  _latestValue: Object;
+  _latestReturnedValue: Object;
+  _sourcePromise: Promise<any>;
+
+  constructor(ref: ChangeDetectorRef) {
+    super();
+    this._ref = ref;
+    this._latestValue = null;
+    this._latestReturnedValue = null;
+  }
+
+  supports(promise): boolean { return PromiseWrapper.isPromise(promise); }
+
+  onDestroy(): void {
+    // NO-OP
+  }
+
+  transform(promise: Promise<any>): any {
+    var pipe = this;
+    if (isBlank(this._sourcePromise)) {
+      this._sourcePromise = promise;
+      promise.then((val) => {
+        if (pipe._sourcePromise === promise) {
+          pipe._updateLatestValue(val);
+        }
+      });
+      return null;
+    }
+
+    if (promise !== this._sourcePromise) {
+      this._sourcePromise = null;
+      return this.transform(promise);
+    }
+
+    if (this._latestValue === this._latestReturnedValue) {
+      return this._latestReturnedValue;
+    } else {
+      this._latestReturnedValue = this._latestValue;
+      return WrappedValue.wrap(this._latestValue);
+    }
+  }
+
+  _updateLatestValue(value: Object) {
+    this._latestValue = value;
+    this._ref.requestCheck();
+  }
+}
+
+/**
+ * Provides a factory for [PromisePipe].
+ *
+ * @exportedAs angular2/pipes
+ */
+export class PromisePipeFactory {
+  supports(promise): boolean { return PromiseWrapper.isPromise(promise); }
+
+  create(cdRef): Pipe { return new PromisePipe(cdRef); }
+}