Replace When.js with ES6 Promise

This shaves the minified browser build down from 42 kB to 12 kB.

README.md

@@ -86,8 +86,13 @@ yarn build
   const Mopidy = new Mopidy(...);
   ```
 
+- **Backwards incompatible:** The `Mopidy` class no longer reexports When.js
+  as `Mopidy.when()`. To upgrade existing code, either migrate to standard
+  ES6 `Promise` or add When.js as a dependency to your project.
+
 - Modernized dependencies:
 
+  - The `Promise` object standardized in ES6 has replaced When.js.
   - `isomorphic-ws` and `ws` has replaced our own wrapper around the browser's
     `WebSocket` API and `faye-websocket` on Node.
 

__tests__/mopidy.test.js

@@ -1,4 +1,3 @@
-const when = require("when");
 const Mopidy = require("../src/mopidy");
 
 const warn = jest.spyOn(global.console, "warn").mockImplementation(() => {});
@@ -192,16 +191,16 @@ describe("._cleanup", () => {
     this.mopidy._cleanup(closeEvent);
 
     expect(Object.keys(this.mopidy._pendingRequests).length).toBe(0);
-    when
-      .settle([promise1, promise2])
-      .then(descriptors => {
-        expect(descriptors.length).toBe(2);
-        descriptors.forEach(d => {
-          expect(d.state).toBe("rejected");
-          expect(d.reason).toBeInstanceOf(Error);
-          expect(d.reason).toBeInstanceOf(Mopidy.ConnectionError);
-          expect(d.reason.message).toBe("WebSocket closed");
-          expect(d.reason.closeEvent).toBe(closeEvent);
+    Promise.all([
+      promise1.catch(error => error),
+      promise2.catch(error => error),
+    ])
+      .then(errors => {
+        errors.forEach(error => {
+          expect(error).toBeInstanceOf(Error);
+          expect(error).toBeInstanceOf(Mopidy.ConnectionError);
+          expect(error.message).toBe("WebSocket closed");
+          expect(error.closeEvent).toBe(closeEvent);
         });
       })
       .then(done);
@@ -697,7 +696,7 @@ describe("._getApiSpec", () => {
     const methods = {};
     const sendStub = jest
       .spyOn(this.mopidy, "_send")
-      .mockReturnValue(when.resolve(methods));
+      .mockReturnValue(Promise.resolve(methods));
     const createApiStub = jest
       .spyOn(this.mopidy, "_createApi")
       .mockImplementation(() => {});
@@ -910,9 +909,3 @@ describe("._createApi", () => {
     });
   });
 });
-
-describe("Reexports", () => {
-  test("Reexports When.js", () => {
-    expect(Mopidy.when()).toEqual(when());
-  });
-});

package.json

@@ -40,7 +40,6 @@
   "dependencies": {
     "bane": "~1.1.0",
     "isomorphic-ws": "^4.0.1",
-    "when": "~3.7.2",
     "ws": "^6.1.0"
   },
   "devDependencies": {

src/mopidy.js

@@ -1,5 +1,4 @@
 const bane = require("bane");
-const when = require("when");
 const WebSocket = require("isomorphic-ws");
 
 class Mopidy {
@@ -130,25 +129,29 @@ class Mopidy {
   _send(message) {
     switch (this._webSocket.readyState) {
       case Mopidy.WebSocket.CONNECTING:
-        return when.reject(
+        return Promise.reject(
           new Mopidy.ConnectionError("WebSocket is still connecting")
         );
       case Mopidy.WebSocket.CLOSING:
-        return when.reject(new Mopidy.ConnectionError("WebSocket is closing"));
+        return Promise.reject(
+          new Mopidy.ConnectionError("WebSocket is closing")
+        );
       case Mopidy.WebSocket.CLOSED:
-        return when.reject(new Mopidy.ConnectionError("WebSocket is closed"));
+        return Promise.reject(
+          new Mopidy.ConnectionError("WebSocket is closed")
+        );
       default:
     }
     const jsonRpcMessage = {
       ...message,
       jsonrpc: "2.0",
       id: this._nextRequestId(),
     };
-    const deferred = when.defer();
-    this._pendingRequests[jsonRpcMessage.id] = deferred.resolver;
-    this._webSocket.send(JSON.stringify(jsonRpcMessage));
-    this.emit("websocket:outgoingMessage", jsonRpcMessage);
-    return deferred.promise;
+    return new Promise((resolve, reject) => {
+      this._pendingRequests[jsonRpcMessage.id] = { resolve, reject };
+      this._webSocket.send(JSON.stringify(jsonRpcMessage));
+      this.emit("websocket:outgoingMessage", jsonRpcMessage);
+    });
   }
 
   _handleMessage(message) {
@@ -233,14 +236,14 @@ class Mopidy {
         return this._send(message);
       }
       if (args.length > 1) {
-        return when.reject(
+        return Promise.reject(
           new Error(
             "Expected zero arguments, a single array, or a single object."
           )
         );
       }
       if (!Array.isArray(args[0]) && args[0] !== Object(args[0])) {
-        return when.reject(new TypeError("Expected an array or an object."));
+        return Promise.reject(new TypeError("Expected an array or an object."));
       }
       [message.params] = args;
       return this._send(message);
@@ -314,8 +317,6 @@ Mopidy.ServerError = ServerError;
 
 Mopidy.WebSocket = WebSocket;
 
-Mopidy.when = when;
-
 Mopidy.prototype._nextRequestId = (() => {
   let lastUsed = -1;
   return () => {

yarn.lock

@@ -7334,11 +7334,6 @@ whatwg-url@^7.0.0:
     tr46 "^1.0.1"
     webidl-conversions "^4.0.2"
 
-when@~3.7.2:
-  version "3.7.8"
-  resolved "https://registry.yarnpkg.com/when/-/when-3.7.8.tgz#c7130b6a7ea04693e842cdc9e7a1f2aa39a39f82"
-  integrity sha1-xxMLan6gRpPoQs3J56Hyqjmjn4I=
-
 whet.extend@~0.9.9:
   version "0.9.9"
   resolved "https://registry.yarnpkg.com/whet.extend/-/whet.extend-0.9.9.tgz#f877d5bf648c97e5aa542fadc16d6a259b9c11a1"