Merge pull request #65 from MichaelDeBoey/add-callbackify-promisify-t…

…o-util

feat(util): add `callbackify` & `promisify`

polyfills/constants.js

@@ -173,7 +173,7 @@ export var UV_FS_COPYFILE_FICLONE = 2;
 export var COPYFILE_FICLONE = 2;
 export var UV_FS_COPYFILE_FICLONE_FORCE = 4;
 export var COPYFILE_FICLONE_FORCE = 4;
-export var OPENSSL_VERSION_NUMBER = 269488351;
+export var OPENSSL_VERSION_NUMBER = 269488335;
 export var SSL_OP_ALL = 2147485780;
 export var SSL_OP_ALLOW_NO_DHE_KEX = 1024;
 export var SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION = 262144;

polyfills/util.js

@@ -19,6 +19,17 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 import process from 'process';
+
+var getOwnPropertyDescriptors = Object.getOwnPropertyDescriptors ||
+  function getOwnPropertyDescriptors(obj) {
+    var keys = Object.keys(obj);
+    var descriptors = {};
+    for (var i = 0; i < keys.length; i++) {
+      descriptors[keys[i]] = Object.getOwnPropertyDescriptor(obj, keys[i]);
+    }
+    return descriptors;
+  };
+
 var formatRegExp = /%[sdj%]/g;
 export function format(f) {
   if (!isString(f)) {
@@ -572,6 +583,111 @@ function hasOwnProperty(obj, prop) {
   return Object.prototype.hasOwnProperty.call(obj, prop);
 }
 
+var kCustomPromisifiedSymbol = typeof Symbol !== 'undefined' ? Symbol('util.promisify.custom') : undefined;
+
+export function promisify(original) {
+  if (typeof original !== 'function')
+    throw new TypeError('The "original" argument must be of type Function');
+
+  if (kCustomPromisifiedSymbol && original[kCustomPromisifiedSymbol]) {
+    var fn = original[kCustomPromisifiedSymbol];
+    if (typeof fn !== 'function') {
+      throw new TypeError('The "util.promisify.custom" argument must be of type Function');
+    }
+    Object.defineProperty(fn, kCustomPromisifiedSymbol, {
+      value: fn, enumerable: false, writable: false, configurable: true
+    });
+    return fn;
+  }
+
+  function fn() {
+    var promiseResolve, promiseReject;
+    var promise = new Promise(function (resolve, reject) {
+      promiseResolve = resolve;
+      promiseReject = reject;
+    });
+
+    var args = [];
+    for (var i = 0; i < arguments.length; i++) {
+      args.push(arguments[i]);
+    }
+    args.push(function (err, value) {
+      if (err) {
+        promiseReject(err);
+      } else {
+        promiseResolve(value);
+      }
+    });
+
+    try {
+      original.apply(this, args);
+    } catch (err) {
+      promiseReject(err);
+    }
+
+    return promise;
+  }
+
+  Object.setPrototypeOf(fn, Object.getPrototypeOf(original));
+
+  if (kCustomPromisifiedSymbol) Object.defineProperty(fn, kCustomPromisifiedSymbol, {
+    value: fn, enumerable: false, writable: false, configurable: true
+  });
+  return Object.defineProperties(
+    fn,
+    getOwnPropertyDescriptors(original)
+  );
+}
+
+promisify.custom = kCustomPromisifiedSymbol;
+
+function callbackifyOnRejected(reason, cb) {
+  // `!reason` guard inspired by bluebird (Ref: https://goo.gl/t5IS6M).
+  // Because `null` is a special error value in callbacks which means "no error
+  // occurred", we error-wrap so the callback consumer can distinguish between
+  // "the promise rejected with null" or "the promise fulfilled with undefined".
+  if (!reason) {
+    var newReason = new Error('Promise was rejected with a falsy value');
+    newReason.reason = reason;
+    reason = newReason;
+  }
+  return cb(reason);
+}
+
+export function callbackify(original) {
+  if (typeof original !== 'function') {
+    throw new TypeError('The "original" argument must be of type Function');
+  }
+
+  // We DO NOT return the promise as it gives the user a false sense that
+  // the promise is actually somehow related to the callback's execution
+  // and that the callback throwing will reject the promise.
+  function callbackified() {
+    var args = [];
+    for (var i = 0; i < arguments.length; i++) {
+      args.push(arguments[i]);
+    }
+
+    var maybeCb = args.pop();
+    if (typeof maybeCb !== 'function') {
+      throw new TypeError('The last argument must be of type Function');
+    }
+    var self = this;
+    var cb = function() {
+      return maybeCb.apply(self, arguments);
+    };
+    // In true node style we process the callback on `nextTick` with all the
+    // implications (stack, `uncaughtException`, `async_hooks`)
+    original.apply(this, args)
+      .then(function(ret) { process.nextTick(cb.bind(null, null, ret)) },
+        function(rej) { process.nextTick(callbackifyOnRejected.bind(null, rej, cb)) });
+  }
+
+  Object.setPrototypeOf(callbackified, Object.getPrototypeOf(original));
+  Object.defineProperties(callbackified, getOwnPropertyDescriptors(original));
+  return callbackified;
+}
+
 export default {
   inherits: inherits,
   _extend: _extend,
@@ -594,5 +710,7 @@ export default {
   inspect: inspect,
   deprecate: deprecate,
   format: format,
-  debuglog: debuglog
+  debuglog: debuglog,
+  promisify: promisify,
+  callbackify: callbackify,
 }