Merge pull request #154 from ParsePlatform/andrewi.promise_constructor

Allow ES6-style Promise construction

Author: peterdotjs

src/ParsePromise.js

@@ -26,11 +26,15 @@ var isPromisesAPlusCompliant = true;
  * @constructor
  */
 export default class ParsePromise {
-  constructor() {
+  constructor(executor) {
     this._resolved = false;
     this._rejected = false;
     this._resolvedCallbacks = [];
     this._rejectedCallbacks = [];
+
+    if (typeof executor === 'function') {
+      executor(this.resolve.bind(this), this.reject.bind(this));
+    }
   }
 
   /**
@@ -301,6 +305,26 @@ export default class ParsePromise {
     return promise;
   }
 
+  /**
+   * Returns a new promise that is resolved with a given value.
+   * If that value is a thenable Promise (has a .then() prototype
+   * method), the new promise will be chained to the end of the
+   * value.
+   * @method resolve
+   * @param value The value to resolve the promise with
+   * @static
+   * @return {Parse.Promise} the new promise.
+   */
+  static resolve(value) {
+    return new ParsePromise((resolve, reject) => {
+      if (ParsePromise.is(value)) {
+        value.then(resolve, reject);
+      } else {
+        resolve(value);
+      }
+    });
+  }
+
   /**
    * Returns a new promise that is rejected with a given error.
    * @method error
@@ -314,6 +338,19 @@ export default class ParsePromise {
     return promise;
   }
 
+  /**
+   * Returns a new promise that is rejected with a given error.
+   * This is an alias for Parse.Promise.error, for compliance with
+   * the ES6 implementation.
+   * @method reject
+   * @param error The error to reject the promise with
+   * @static
+   * @return {Parse.Promise} the new promise.
+   */
+  static reject(...errors) {
+    return ParsePromise.error.apply(null, errors);
+  }
+
   /**
    * Returns a new promise that is fulfilled when all of the input promises
    * are resolved. If any promise in the list fails, then the returned promise

src/__tests__/ParsePromise-test.js

@@ -430,5 +430,57 @@ describe('Promise', () => {
     expect(ParsePromise.is({})).toBe(false);
     expect(ParsePromise.is(ParsePromise.as())).toBe(true);
     expect(ParsePromise.is(ParsePromise.error())).toBe(true);
-  })
+  });
+
+  it('can be constructed in ES6 style and resolved', asyncHelper((done) => {
+    expect(ParsePromise.length).toBe(1); // constructor arguments
+
+    new ParsePromise((resolve, reject) => {
+      resolve('abc');
+    }).then((result) => {
+      expect(result).toBe('abc');
+      
+      return new ParsePromise((resolve, reject) => {
+        resolve('def');
+      });
+    }).then((result) => {
+      expect(result).toBe('def');
+      done();
+    });
+  }));
+
+  it('can be constructed in ES6 style and rejected', asyncHelper((done) => {
+    new ParsePromise((resolve, reject) => {
+      reject('err');
+    }).then(() => {
+      // Should not be reached
+    }, (error) => {
+      expect(error).toBe('err');
+      
+      return new ParsePromise((resolve, reject) => {
+        reject('err2');
+      });
+    }).then(null, (error) => {
+      expect(error).toBe('err2');
+      done();
+    });
+  }));
+
+  it('can be initially resolved, ES6 style', asyncHelper((done) => {
+    ParsePromise.resolve('abc').then((result) => {
+      expect(result).toBe('abc');
+      
+      return ParsePromise.resolve(ParsePromise.as('def'));
+    }).then((result) => {
+      expect(result).toBe('def');
+      done();
+    });
+  }));
+
+  it('can be initially rejected, ES6 style', asyncHelper((done) => {
+    ParsePromise.reject('err').then(null, (error) => {
+      expect(error).toBe('err');
+      done();
+    });
+  }));
 });