1676283 - Don't bail out when MarionetteEvents actor is registered more than once

Status: RESOLVED FIXED

(Remote Protocol :: Marionette, task, P3)

Description

[Julian Descottes [:jdescottes]]

From https://phabricator.services.mozilla.com/D96117#inline-543242

We are adding a set of helpers registerEventsActor & unregisterEventsActor to MarionetteEventsParent.jsm in Bug 1675320.

In theory registerEventsActor should never be called twice in a row without calling unregisterEventsActor. If we call it twice, the second call will throw because actors can only be registered once.

We should handle this case properly. Either silently skip the registration if the actor is already registered, or throw a meaningful error. The choice between the two options depends on whether or not we consider that it is valid to call registerEventsActor twice.

Comment 1

[Henrik Skupin [:whimboo][⌚️UTC+1]]

By using a reference counter we can decide when the actor needs to be registered or unregistered.

Comment 2

[Henrik Skupin [:whimboo][⌚️UTC+1]]

Whereby I wonder if the ref counting logic would make sense. The actor gets swapped anyway with the next page load, so maybe we should not explicitly unregister again, but just ignore the already registered error?

Comment 3

[Henrik Skupin [:whimboo][⌚️UTC+1]]

Actually I think it should be ok to not care about ref counters, at least not for now. Reason is that the actor gets destroyed anyway with the next navigation, and it is small enough to not require too much memory. As such I will update one of my patches on bug 1669169 to just reference this bug. It will make sure to silently ignore a possible re-registration of the actor by filtering out a thrown NotSupportedError error.

Comment 4

[Henrik Skupin [:whimboo][⌚️UTC+1]]

Attachment: Bug 1676283 - [marionette] Hardening registration and unregistration of MarionetteEvents actor.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/944bb44d0883
[marionette] Hardening registration and unregistration of MarionetteEvents actor. r=marionette-reviewers,jdescottes

Comment 6

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/944bb44d0883