Firefox native messaging through webextension - firefox-addon

Question

Created a webextension for firefox (currently using Nightly 52), that uses native messaging to launch a java program on Linux (Ubuntu 14, 32x).
The webextension loads, reads the .json file and reads the path which points to a script that starts the java program. The JSON and the path are correct as when I use:
var native = browser.runtime.connectNative("passwordmanager");
console.log("native.name" + native.name); //outputs passwordmanager.
native.onDisconnect.addListener(function(m) { console.log("Disconnected"); });
The above code prints the name of the native port and also prints "Disconnected". So I m guessing the native app is terminating for some reason.
The application is only skeleton right now, that just does sysout and reads sysin and works correctly if Launch it directly through the shell script.
While debugging the webextension, I am not able to step into the call to connectNative, as it just steps-over that call instead of doing step-in. So kind of out of options whats' going wrong.
Please let me know if anyone is able to create a native messaging app based on FF webextension and any pointers on what I might be doing wrong.
Thanks

Answer 1

This solution here shows you how to detect onConnect and onFail. It should help you out to figure out your real problem.
So I don't think you can do proper error handling with connectNative from the JS side alone. You can do somewhat error handling if you get the exe side involved, but you can't get a string for "error reason" when an error occurs. The error is only logged to console.
First make sure to set your deeloper prefs, so messages show in your browser console. You can use this addon - https://addons.mozilla.org/en-US/firefox/addon/devprefs/ - or read that addon description it gives you the MDN page with the prefs to set.
Then this is how you can do some sort of error handling (without error reason) (pseudo-code - i might need a .bind in the callbcks):
function connectNative(aAppName, onConnect, onFail) {
var listener = function(payload) {
if (!connected) {
connected = true;
port.onDisconnect.removeListener(failedConnect);
onConnect();
} else {
// process messages
}
}
var failedConnect = function() {
onFail('failed for unattainable reason - however see browser console as it got logged there');
}
var connected = false;
var port = chrome.runtime.connectNative(aAppName);
port.onMessage.addListener(listener);
port.onDisconnect.addListener(failedConnect);
return port;
}
Now in your exe, as soon as it starts up, make it write to stdout something. That will trigger the onConnect.