Can not get responses in Popup script

[pangmaowang]

Describe the bug

Hi, I am new to extension dev, I am following the examples in background forward message, but the popup can not get the message, I am bit confused what's happening here.

Based on the code, I am expecting it should receive a response and display it, but the response is actually undefined here.

I tried the suggestion here but it is still not working..
#971

Reproduction

https://github.com/wxt-dev/examples/tree/main/examples/background-message-forwarder

Steps to reproduce

run the example, see if you could get the response displayed

System Info

System:
    OS: macOS 15.2
    CPU: (10) arm64 Apple M4
    Memory: 319.52 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.12.0 - ~/.nvm/versions/node/v22.12.0/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.9.0 - ~/.nvm/versions/node/v22.12.0/bin/npm
    pnpm: 8.6.2 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 131.0.6778.205
    Safari: 18.2

Used Package Manager

npm

Validations

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• Read the docs.
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• The provided reproduction is a minimal reproducible example of the bug.

[pangmaowang]

Finally got it working after debugging for the whole afternoon..
It seems the example no longer works the way it’s written—correct me if I’m wrong.
Chrome requires a synchronous return of true or false:
false: The channel closes immediately (suitable for synchronous code).
true: The channel remains open (suitable for asynchronous code).
Workaround:
Instead of making the listener async, we can return true to keep the channel open and then handle the async logic in a separate async function.

[aklinker1]

If you're using extensionApi: "chrome", you'll need to use a synchronous callback, return true, and use sendResponse as you described. The example should work just fine since it uses the webextension-polyfill, but it should be updated so it works with both APIs using sendResponse, especially since v0.20 will be changing the default.

[pangmaowang]

Thanks for the detailed explanation! I didn’t realize it was the config extension difference that caused it to stop working.

It’s great to learn something new about extension development—really appreciate your insights