1131428 - WindowsPreviewPerTab.jsm's _imageFromURI doesn't always call its callback

Status: NEW

(Firefox :: Shell Integration, defect, P5)

Description

[Blair McBride [:Unfocused] (UNAVAILABLE)]

In WindowsPreviewPerTab.jsm, the callback passed to _imageFromURI isn't guarenteed to be called. This isn't a particularly bad problem right now, but the code isn't intentional about what it does and this is a footgun.


As discussed in bug 1130816 comment 11:

> (In reply to :Gijs Kruitbosch from comment #9)
> > 1) the resultcode of the fetch != NS_OK, in which case we just bail and
> > don't call the callback. Considering the callbacks here only update the icon
> > if it's non-empty, leaving it empty seems... OK?
> > 2) if fetching the icon for the default favicon URI failed. Obviously, that
> > shouldn't happen... but if it did, I guess leaving the icon un-set would
> > also probably be the sensible approach, rather than just trying again?
> 
> Yea, I don't think those are particularly bad. I guess there's the question
> of whether a stale image or no image is a better fail-mode.
> 
> But what worries me is that the code isn't being intentional about it.
> That's going to bite us on our collective asses in the future.