scratchfoundation/scratch-vm
1
0
Fork 0
mirror of https://github.com/scratchfoundation/scratch-vm.git synced 2025-08-13 06:49:19 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions1

Add tests for message dispatch system; fix bugs

Browse source 
The tests run using TinyWorker, which emulates web workers on Node.
There are quite a few quirks in that situation due to the differences
between Node and Webpack as well as the differences between TinyWorker
and real Web Workers.

The tests also exposed a few bugs in the dispatch system, which have now
been fixed. Most notably, if a method called through the dispatch system
throws an exception that exception will now be passed back to the
caller. Previously the exception would escape the dispatch system and
the caller would never hear any response at all.
This commit is contained in:
Christopher Willis-Ford 2017-07-15 23:51:59 -07:00
parent 09d3fe330f
commit 0fcc248ac1
7 changed files with 160 additions and 53 deletions
src/dispatch
worker-dispatch.js

55
src/dispatch/worker-dispatch.js
View file

@ -12,7 +12,7 @@ class WorkerDispatch {
/**
* List of callback registrations for promises waiting for a response from a call to a service on another
* worker. A callback registration is an array of [resolve,reject] Promise functions.
* Calls to services on this worker don't enter this list.
* Calls to local services don't enter this list.
* @type {Array.<[Function,Function]>}
*/
this.callbacks = [];
@ -25,8 +25,6 @@ class WorkerDispatch {
*/
this._connectionPromise = new Promise(resolve => {
this._onConnect = resolve;
}).then(() => {
self.onmessage = this._onMessage.bind(this);
});
/**
@ -44,7 +42,10 @@ class WorkerDispatch {
*/
this.services = {};
self.onmessage = this._onHandshake.bind(this);
this._onMessage = this._onMessage.bind(this);
if (typeof self !== 'undefined') {
self.onmessage = this._onMessage;
}
}
/**
@ -94,18 +95,22 @@ class WorkerDispatch {
*/
transferCall (service, method, transfer, ...args) {
return new Promise((resolve, reject) => {
if (this.services.hasOwnProperty(service)) {
const provider = this.services[service];
const result = provider[method].apply(provider, args);
resolve(result);
} else {
const callbackId = this.nextCallback++;
this.callbacks[callbackId] = [resolve, reject];
if (transfer) {
self.postMessage([service, method, callbackId, ...args], transfer);
try {
if (this.services.hasOwnProperty(service)) {
const provider = this.services[service];
const result = provider[method].apply(provider, args);
resolve(result);
} else {
self.postMessage([service, method, callbackId, ...args]);
const callbackId = this.nextCallback++;
this.callbacks[callbackId] = [resolve, reject];
if (transfer) {
self.postMessage([service, method, callbackId, ...args], transfer);
} else {
self.postMessage([service, method, callbackId, ...args]);
}
}
} catch (e) {
reject(e);
}
});
}
@ -126,20 +131,6 @@ class WorkerDispatch {
});
}
/**
* Message handler active until the dispatcher handshake arrives.
* @param {MessageEvent} event - the message event to be handled.
* @private
*/
_onHandshake (event) {
const message = event.data;
if (message === 'dispatch-handshake') {
this._onConnect();
} else {
log.error(`WorkerDispatch received unexpected message before handshake: ${JSON.stringify(message)}`);
}
}
/**
* Message handler active after the dispatcher handshake. This only handles method calls.
* @param {MessageEvent} event - the message event to be handled.
@ -149,6 +140,9 @@ class WorkerDispatch {
const [service, method, callbackId, ...args] = /** @type {[string, string, *]} */ event.data;
if (service === 'dispatch') {
switch (method) {
case '_handshake':
this._onConnect();
break;
case '_callback':
this._callback(callbackId, ...args);
break;
@ -184,7 +178,4 @@ class WorkerDispatch {
}
}
const dispatch = new WorkerDispatch();
module.exports = dispatch;
self.Scratch = self.Scratch || {};
self.Scratch.dispatch = dispatch;
module.exports = new WorkerDispatch();