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AsyncEmitter #427

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AsyncEmitter #427

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tshemsedinov
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ee.on('e1', async () => true);
await ee.emit('a1');

I suppose we need to hide counters when waiting for multiple event handlers to this abstraction.

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@tshemsedinov tshemsedinov changed the title AsyncEventEmitter AsyncEmitter Jun 3, 2019
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@tshemsedinov tshemsedinov self-assigned this Jun 3, 2019
@tshemsedinov tshemsedinov force-pushed the async-ee branch 2 times, most recently from 1d27b1e to 4102ef3 Compare June 4, 2019 07:58
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@tshemsedinov
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I added tests that reveal problems and now it’s clear that we need to change data structure for wrappers. Maybe better store them mixed to functions: fn[symbolWrapper] = wrapper ? @nechaido @belochub @lundibundi

@tshemsedinov
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Implemented in a different way. Now we hold on and once in different data structures for each event separately:

AsyncEmitter {
  events:
    Map {
      'eventName' => {
        on: Set { listener<Function> },
        once: Map { listener<Function> => wrapper<Function> }
      },
  }
}

@nechaido @belochub @lundibundi

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Co-Authored-By: Denys Otrishko <shishugi@gmail.com>
Co-Authored-By: Mykola Bilochub <nbelochub@gmail.com>
Co-Authored-By: Dmytro Nechai <nechaido@gmail.com>
const event = this.events.get(name);
if (!event) return 0;
const { on, once } = event;
return on.size + once.size;
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Nit: can be simplified to:

return event ? event.on.size + event.once.size : 0;

// Get or create event
// name <string> event name
// Returns: { on: <Set>, once: <Set> } }
event(name) {
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I'd prefer to use Symbol('getListeners') for this, to make this property "private".


class AsyncEmitter {
constructor() {
this.events = new Map();
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Suggested change
this.events = new Map();
this.listeners = new Map();

if (!event) return Promise.resolve();
const { on, once } = event;
const promises = [...on, ...once].map(fn => fn(...args));
once.clear();
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I'd prefer to move this one line up, because some of the listeners may create additional once listeners.

metatests.test('AsyncEmitter on/emit', async test => {
const ae = new AsyncEmitter();

const fn = test.mustCall(async (a, b, c, d) => {
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?

Suggested change
const fn = test.mustCall(async (a, b, c, d) => {
const fn = test.mustCall(async (...args) => { test.strictSame(args, [1, 2, 3, 4]) });


metatests.test('AsyncEmitter once', async test => {
const ae = new AsyncEmitter();

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You should add a test, to ensure that emit args are forwarded to once listener.

once(name, fn) {
if (fn === undefined) {
return new Promise(resolve => {
this.once(name, resolve);
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Suggested change
this.once(name, resolve);
this.once(name, (...args) => resolve(args.length <= 1 ? args[0] : args)
);

});

setTimeout(fn, 0);
await ae.once('e1');
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Ditto.

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4 participants