Is Components.utils.unload asynchronous in Firefox bootstrapped extensions?

Question

I noticed an occasional error logged on disabling the bootstrapped addon.

function shutdown:

function shutdown(data, reason) {

  forEachOpenWindow(unloadFromWindow);
  Services.wm.removeListener(WindowListener);
  Components.utils.unload('chrome://myaddon/content/main.jsm');
}

Sometimes, it came up with an error on disabling the addon:

NotFoundError: Node was not found main.jsm:112

Is it that the Components.utils.unload() is asynchronous?

1- Is that the case or is it due to some other issue?
2- If that is the case, how should it be dealt with?
3- Can the Components.utils.unload() be added to (processed in) the JSM that it is removing (removing itself)?
4- Any other suggestions?

Update:

Next test:
Disable -- no error
Enable/Disable -- 1 error (above)
Enable/Disable -- 2 error (above)
Enable/Disable -- 3 error (above)
Enable/Disable -- 4 error (above)
Enable/Disable -- 5 error (above)

Now that is strange ....

Update 2:
I found the problem.... typo/error in one of the listeners so it was NOT removed on shutdown() and with every subsequent enable/disable one more listeners was added...that was why the number of errors increased each time :)

While I can answer the question from your title, I cannot really comment on the sub-questions of why your code is broken: You simply did not provide enough code. Please update your question. — nmaier
Not enough. To debug actual code, actual code is needed. I also don't think the problem is with Cu.unload. — nmaier
Maybe ... I will look further into it but the (occasional) error goes away if Components.utils.unload('chrome://myaddon/content/main.jsm'); is commented out. Also, since console is undefined the error is not with the code itself ;) — erosman
@nmaier ... never mind... I found the problem...damn typo/error in one of the listeners so it was NOT removed on shutdown() and with every subsequent enable/disable one more listeners was added..that was why the number of errors increase each time :D — erosman

nmaier nmaier · Accepted Answer · 2014-06-30T08:11:27

Is Components.utils.unload asynchronous in Firefox bootstrapped extensions?

Cu.unload is not asynchronous. But also, it might not do what you expect.

It will just instruct the module loader to forget about it. Any references to the module instance from other code will still work, i.e. the module instance will be alive until all other references to it are gone and it can be garbage collected.

In that regard it can seem like unload is kinda asynchronous.

3- Can the Components.utils.unload() be added to (processed in) the JSM that it is removing (removing itself)?

Yes, the module can Cu.unload on itself. Code after Cu.unload will still work (see also the first part of my answer).

Is Components.utils.unload asynchronous in Firefox bootstrapped extensions?

1 Answers