Reply send from runtime.onMessage handler is not received by sender

Question

Created Sep ’20

Replies 2

Boosts 0

Views 3.2k

Participants 4

I'm converting my extensions and I've noticed that no reply is being send when I send message between different contexts of my extension.

Steps to reproduce:
1) open background script console and execute:

Code Block browser.runtime.onMessage.addListener(x => {
  if (x === 'hello') {
    console.warn(x);
    return Promise.resolve('ok');
  }
});

2) open extension page and in the console execute this:

Code Block await browser.runtime.sendMessage('hello');

Background console will correctly print "hello" but the extension page won't receive the reply "ok".

Is sending responses from runtime.onMessage handler not supported in Safari?
MDN: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/onMessage

Answered by adomasven in 634052022

You can get the responses to work by using the sendResponse callback. If you look at the browser compatibility table for onMessage listener you will see that responses via promises only natively work on Firefox (and if you're using a browser. polyfill then the promise response works for chrome too).
You can do something like this for safari:

Code Block browser.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (x === 'hello') {
    console.warn(x);
    performAsyncOperation(function callback() { sendResponse('ok') })
    // need to return true if you plan on sending a response asynchronously
    return true;
  }
  if (x === 'bye') {
    sendResponse('ok')
    // no need to return anything here, since we send the response synchronously
  }
});

Answer 1 · Sep 18, 2020 02:47 PM

adomasven OP

Sep ’20

Accepted Answer

You can get the responses to work by using the sendResponse callback. If you look at the browser compatibility table for onMessage listener you will see that responses via promises only natively work on Firefox (and if you're using a browser. polyfill then the promise response works for chrome too).
You can do something like this for safari:

Code Block browser.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (x === 'hello') {
    console.warn(x);
    performAsyncOperation(function callback() { sendResponse('ok') })
    // need to return true if you plan on sending a response asynchronously
    return true;
  }
  if (x === 'bye') {
    sendResponse('ok')
    // no need to return anything here, since we send the response synchronously
  }
});

Answer 2 · Sep 21, 2020 11:39 AM

Frameworks Engineer OP

Apple

Sep ’20

Promises are natively supported by Safari too. This might be a bug. Can you send a sample extension via Feedback Assistant so we can look at fixing this? Thanks!