ipcRenderer.callMain - subsequent calls return non-resolving Promises

[maciejewiczow]

When ipcRenderer.callMain gets called two or more times, the first Promise resolves normally, but subsequent calls return non-resolving Promises. I'm using typescript and electron-webpack. I've thrown together a quick bug repro repo to ilustrate the problem. I did a bit of investigation around the method's source code and found out that in the second call, the callbacks (onData, onError) were not called. But, when I commented out these lines, the issue disappeared (at least for my test case)

ipc.callMain = (channel, data) => new Promise((resolve, reject) => {
    const {sendChannel, dataChannel, errorChannel} = util.getResponseChannels(channel);

    const cleanup = () => {
-       ipc.off(dataChannel, onData);
-       ipc.off(errorChannel, onError);
+       // ipc.off(dataChannel, onData);
+       // ipc.off(errorChannel, onError);
    };

    const onData = (event, result) => {
        cleanup();
        resolve(result);
    };

    const onError = (event, error) => {
        cleanup();
        reject(deserializeError(error));
    };

    ipc.once(dataChannel, onData);
    ipc.once(errorChannel, onError);

In my opinion the off calls are redundant anyways, because the listeners are attached using once, so they will be removed automatically after first event regardless (and that's what happens after my change, as far as I know). I feel like the double removal might be the issue here.

[sindresorhus]

In my opinion the off calls are redundant anyways,

No. Without the cleanup, if data is called, the error one is never cleaned up.

[maciejewiczow]

Okay, I haven't thought of this. But nonetheless, something strange is going on here. After another bit of poking around I discovered that adding any listener to ipc emitter before first call to callMain also fixes this issue. I have even less of an idea now as to what might be the cause of this behavior.

[danwt]

I have the same issue

[maciejewiczow]

For now, my temporary workaround around the issue is to put the following code in the root file of the part of the project that uses electron-better-ipc

if (ipcMain !== undefined)
    ipcMain.addListener('fix-event-798e09ad-0ec6-5877-a214-d552934468ff', () => {});

if (ipcRenderer !== undefined)
    ipcRenderer.addListener('fix-event-79558e00-29ef-5c7f-84bd-0bcd9a0c5cf3', () => {});

No idea why this changes anything though, just stumbled upon it randomly

[pixelart7]

I am having similar issue, and I can confirm that the workaround is working.

[mferris77]

Also confirming the workaround solves this issue. This is the code at the top of my file where I invoke electron-better-ipc:

const { app, remote, ipcMain, ipcRenderer } = require("electron");
const { ipcRenderer: ipc } = require("electron-better-ipc");

// fix for electron-better-ipc
// from https://github.com/sindresorhus/electron-better-ipc/issues/35
if (ipcMain !== undefined)
  ipcMain.addListener(
    "fix-event-798e09ad-0ec6-5877-a214-d552934468ff",
    () => {}
  );

if (ipcRenderer !== undefined)
  ipcRenderer.addListener(
    "fix-event-79558e00-29ef-5c7f-84bd-0bcd9a0c5cf3",
    () => {}
  );
//end fix

[banben]

Have the same problem too.

[tjklemz]

Same. Makes the library unusable. :( The workaround did not work for me.

[cannc4]

I can confirm that the workaround works. Odd solution though :)

[macharborguy]

Confirmed both the bug as well as the workaround being successful.

For those who cannot get the workaround, well, working, make sure that the addListener method is chained after the variable containing the specific IPC.

so if you alias your ipcMain or ipcRenderer methods and rename them to simply 'ipc', you will need to add the listeners to 'ipc'

[gushogg-blake]

Note that you need the applicable part of code in both environments - renderer and main. I have the following:

In src/main.js (main):

let {
    app,
    // etc
    ipcMain,
} = require("electron");

let {ipcMain: ipc} = require("electron-better-ipc");

// HACK for https://github.com/sindresorhus/electron-better-ipc/issues/35
ipcMain.addListener("fix-event-798e09ad-0ec6-5877-a214-d552934468ff", () => {});

In src/app.js (renderer):

// HACK for https://github.com/sindresorhus/electron-better-ipc/issues/35
require("electron").ipcRenderer.addListener("fix-event-79558e00-29ef-5c7f-84bd-0bcd9a0c5cf3", () => {});