forward.js•1.93 kB
import {EventEmitter} from 'node:events';
import {onMessage, onDisconnect} from './incoming.js';
import {undoAddedReferences} from './reference.js';
// Forward the `message` and `disconnect` events from the process and subprocess to a proxy emitter.
// This prevents the `error` event from stopping IPC.
// This also allows debouncing the `message` event.
export const getIpcEmitter = (anyProcess, channel, isSubprocess) => {
if (IPC_EMITTERS.has(anyProcess)) {
return IPC_EMITTERS.get(anyProcess);
}
// Use an `EventEmitter`, like the `process` that is being proxied
// eslint-disable-next-line unicorn/prefer-event-target
const ipcEmitter = new EventEmitter();
ipcEmitter.connected = true;
IPC_EMITTERS.set(anyProcess, ipcEmitter);
forwardEvents({
ipcEmitter,
anyProcess,
channel,
isSubprocess,
});
return ipcEmitter;
};
const IPC_EMITTERS = new WeakMap();
// The `message` and `disconnect` events are buffered in the subprocess until the first listener is setup.
// However, unbuffering happens after one tick, so this give enough time for the caller to setup the listener on the proxy emitter first.
// See https://github.com/nodejs/node/blob/2aaeaa863c35befa2ebaa98fb7737ec84df4d8e9/lib/internal/child_process.js#L721
const forwardEvents = ({ipcEmitter, anyProcess, channel, isSubprocess}) => {
const boundOnMessage = onMessage.bind(undefined, {
anyProcess,
channel,
isSubprocess,
ipcEmitter,
});
anyProcess.on('message', boundOnMessage);
anyProcess.once('disconnect', onDisconnect.bind(undefined, {
anyProcess,
channel,
isSubprocess,
ipcEmitter,
boundOnMessage,
}));
undoAddedReferences(channel, isSubprocess);
};
// Check whether there might still be some `message` events to receive
export const isConnected = anyProcess => {
const ipcEmitter = IPC_EMITTERS.get(anyProcess);
return ipcEmitter === undefined
? anyProcess.channel !== null
: ipcEmitter.connected;
};