Webextension: message passing between a service worker and a web page

[Giacomo Tommaso Petrucci]

Hello everyone,

I'm writing a web extension for Chromium and I'm using a service worker to do some background activities (something that with manifest V2 would have been done using a BackgroundScript). I need to send messages from a script that is injected into a web page to the service worker and get responses back. To do this, inside the injected script I use chrome.runtime.sendMessage like this:

chrome.runtime.sendMessage(extensionID,
{
content: emailBody,
identifiers: recipientsAddressesArray,
request: "encrypt"
}, (response)=>console.log("Got response: ", response)
)

While inside the service worker i have the following code:

import {encrypt, decrypt, getHiddenPolicies} from "./crypto";

chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {

    console.log("Message listener invoked")
})

console.log("Service worker started!")

Now, when the message is sent from the page to the service worker, I get "Got response:  undefined" in the page's console regardless of whether I write code in the message handler to send a response back or not, while if I inspect the service worker output using the devtools, I see "Service worker started!" and some output form the script I'm importing, but no "Message listener invoked". What I'm getting wrong?

Thank you for your help,

Giacomo

[Giacomo Tommaso Petrucci]

Sorry, I found the problem: I have to use chrome.runtime.onMessageExternal.addListener instead of chrome.runtime.onMessage.addListener. I would suggest to have the case of service workers explicitly covered in the docs about message passing here: https://developer.chrome.com/docs/extensions/mv3/messaging/
Now I still have something not working but maybe it's unrelated to message passing, I'll open a new discussion if I need help.
Thanks,

Giacomo