Implement backwards compatible promise support.

Closes #523.

lib/apirequest.js

@@ -17,6 +17,7 @@ var utils = require('./utils.js');
 var DefaultTransporter = require('./transporters.js');
 var stream = require('stream');
 var parseString = require('string-template');
+var Promise = require('bluebird');
 
 function isReadableStream (obj) {
   return obj instanceof stream.Stream &&
@@ -175,16 +176,37 @@ function createAPIRequest (parameters, callback) {
   delete options.auth; // is overridden by our auth code
   delete options.params; // We handle params ourselves and Request does not recognise 'params'
 
+  var resolve, reject;
+
+  // Promisify the results, but also call the node-style callback
+  var promise = new Promise(function () {
+    resolve = arguments[0];
+    reject = arguments[1];
+  }).asCallback(callback, { spread: true });
+
+  // Capture err and/or results
+  var promiseBack = function (err) {
+    if (err) {
+      return reject(err);
+    }
+    return resolve(Array.prototype.slice.call(arguments, 1));
+  };
+
   // create request (using authClient or otherwise and return request obj)
   if (authClient) {
-    req = authClient.request(options, callback);
+    req = authClient.request(options, promiseBack);
   } else {
-    req = new DefaultTransporter().request(options, callback);
+    req = new DefaultTransporter().request(options, promiseBack);
   }
 
-  if (body) {
-    body.pipe(req);
+  if (req) {
+    // Make promise available
+    req.promise = promise;
+    if (body) {
+      body.pipe(req);
+    }
   }
+
   return req;
 }
 

package.json

@@ -61,6 +61,7 @@
   },
   "dependencies": {
     "async": "~1.5.2",
+    "bluebird": "^3.3.5",
     "gapitoken": "~0.1.5",
     "google-auth-library": "~0.9.7",
     "request": "~2.72.0",

test/test.promises.js

@@ -0,0 +1,106 @@
+// Copyright 2013-2016, Google, Inc.
+// 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.
+
+'use strict';
+
+var assert = require('assert');
+var googleapis = require('../');
+var nock = require('nock');
+var utils = require('./utils');
+
+function testInsert (urlshortener) {
+  var obj = { longUrl: 'http://google.com/' };
+  return urlshortener
+    .url
+    .insert({ resource: obj })
+    .promise
+    .spread(function (result) {
+      assert.notEqual(result, null);
+      assert.notEqual(result.kind, null);
+      assert.notEqual(result.id, null);
+      assert.equal(result.longUrl, 'http://google.com/');
+    });
+}
+
+function testBackendError (urlshortener) {
+  var obj = { longUrl: 'http://google.com/' };
+  return urlshortener
+    .url
+    .insert({ resource: obj })
+    .promise
+    .then(function () {
+      throw new Error('should have failed!');
+    }, function (err) {
+      assert(err instanceof Error);
+      assert.equal(err.code, 500);
+      assert.equal(err.message, 'There was an error!');
+    });
+}
+
+describe('Request#toPromise', function () {
+  var localUrlshortener, remoteUrlshortener;
+
+  before(function (done) {
+    nock.cleanAll();
+    var google = new googleapis.GoogleApis();
+    nock.enableNetConnect();
+    utils.loadApi(google, 'urlshortener', 'v1', function (err, urlshortener) {
+      nock.disableNetConnect();
+      if (err) {
+        return done(err);
+      }
+      remoteUrlshortener = urlshortener;
+      done();
+    });
+  });
+
+  beforeEach(function () {
+    nock.cleanAll();
+    nock.disableNetConnect();
+    var google = new googleapis.GoogleApis();
+    localUrlshortener = google.urlshortener('v1');
+  });
+
+  it('should return a single response object for single requests (promises)', function () {
+    var scope = nock('https://www.googleapis.com', {
+      allowUnmocked: true
+    })
+      .post('/urlshortener/v1/url')
+      .times(2)
+      .replyWithFile(200, __dirname + '/fixtures/urlshort-insert-res.json');
+
+    return testInsert(localUrlshortener).then(function () {
+      return testInsert(remoteUrlshortener);
+    }).then(function () {
+      scope.done();
+    });
+  });
+
+  it('should return 5xx responses as errors', function () {
+    var scope = nock('https://www.googleapis.com', { allowUnmocked: true })
+      .post('/urlshortener/v1/url')
+      .times(2)
+      .reply(500, 'There was an error!');
+
+    return testBackendError(localUrlshortener).then(function () {
+      return testBackendError(remoteUrlshortener);
+    }).then(function () {
+      scope.done();
+    });
+  });
+
+  after(function () {
+    nock.cleanAll();
+    nock.enableNetConnect();
+  });
+});