[BUG] Can not send message from content script to background via @plasmohq/messaging

[kingname]

What happened?

A bug happened!

// content.tsx

...
const resp = await sendToBackground({
          name: "getRulesByUrl",
          body: {
            url: window.location.href
          },
          extensionId: "jgcgphlmbjhdhhaamkmiddgbfbkbknan"
        })
        console.log(resp)
        setRules(resp);

// background/getRulesByUrl.ts

import type { PlasmoMessaging } from "@plasmohq/messaging";

const handler: PlasmoMessaging.MessageHandler = async (req, res) => {
    const name = req.name;
    const url = req.body.url;
    const domain = new URL(url).hostname;
    let rules;
    if (url === 'google.com') {
        console.log('hit greenhouse.io! return rules...');
        rules = {
            xxx: true
        }
        res.send(rules)
    }
}

export default handler;

background could not receive any message. instead, an error occur:

Version

Latest

What OS are you seeing the problem on?

MacOSX

What browsers are you seeing the problem on?

Microsoft Edge

Relevant log output

Uncaught (in promise) Error: A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received

(OPTIONAL) Contribution

• [x] I would like to fix this BUG via a PR

Code of Conduct

• [X] I agree to follow this project's Code of Conduct
• [X] I checked the current issues for duplicate problems.

[kingname]

P.S.: It works well when I send message from popup.tsx to background.

Only error from content script to background.

[Acorn221]

Hi there, have you tried doing something like this?

 if (url === 'google.com') {
        console.log('hit greenhouse.io! return rules...');
        rules = {
            xxx: true
        }
        res.send(rules)
    }
    res.send("err, not google"); // ensure a response is sent back in every case

I think if your content script is in the "isolated" world, which it appears to be in, the problem is caused by no response being sent back from your message handler

[kingname]

@Acorn221 Good point. I will make a try this evening. However, why does popup.tsx work well?

[Acorn221]

I can't be sure without seeing the code! Maybe your popup handler always returns something?

[kingname]

@Acorn221 You save me. By using your advice, it works like a charm.