sending a response for async listeners

[opto]

MDN URL

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/onMessageExternal

What specific section or headline is this issue about?

addListener syntax/sendResponse

What information was incorrect, unhelpful, or incomplete?

this sounds like a personal choice (but it is not, see below):

To send a response synchronously, call sendResponse before the listener function returns. To send a response asynchronously, do one of these:

My understanding is that async functions can call sync functions in their inside, so there is no reason why an async listener could not call a sync function sendResponse.

Which means the sending is ended before the next code statement in the async listener. (Sending could just be a handing over to a messaging system, like putting a letter into a physical mailbox of the postal service). No reason why that could not be done sync in the async listener, in theory? It does not seem to be forbidden by JS.

What did you expect to see?

does not work. what is written is valid only for a sync listener.

for an async listener, the message must be returned by the listener statement:

return response;

so there is no choice in this case.

So this is not personal option:

To send a response synchronously, call sendResponse before the listener function returns. To send a response asynchronously, do one of these:

and it might help to rephrase it.

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

No response

MDN metadata

Page report details

• Folder: en-us/mozilla/add-ons/webextensions/api/runtime/onmessageexternal
• MDN URL: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/onMessageExternal
• GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/mozilla/add-ons/webextensions/api/runtime/onmessageexternal/index.md
• Last commit: 4b10cb2
• Document last modified: 2022-11-30T17:53:16.000Z