We have very basic write access check capability in Mozilla. Both the extension manager and app update perform write access checks for the install directory on startup. This should be provided by a single component (perhaps nsIXULAppInfo?) to lessen the times we hit the disk.

Is there a reason that we would still need the hacks we currently use to test write access once bug 437216 is fixed?

That would get us closer though there are other read only filesystems such as flash cards.

I guess what I'm trying to say is that I don't think we should need a separate component for this. nsILocalFile ought to be giving us all of the information we need using the appropriate OS system calls. Maybe we just put the hacky method into there for now.

I'm not so concerned about where it lives though I don't think atm that it should be in nsILocalFile since I think it should be specific for the install directory and the state should be cached to prevent multiple check. I don't think we need a separate component... it could be provided by nsIXULAppInfo for example.