[whatwg] Something better than DOM_QUOTA_ERROR when LocalStorage is immutable?

[Ian Hickson]

On Wed, 3 Jun 2009, Jeremy Orlow wrote:
> 
> When in "private browsing" mode, WebKit should not write any data to the 
> hard drive.  In addition, WebKit does not allow changes to localStorage 
> that aren't going to be written to disk.  Currently, it returns a 
> DOM_QUOTA_ERROR on setItem when private browsing is enabled, and 
> silently fails for removeItem and clear.  The silent failures are 
> obviously bad, but even the (ab)use of DOM_QUOTA_ERROR kind of bothers 
> me.

This model is treating "private browsing" as a user-enabled emulation of a 
hardware limitation (read-only storage media), and as such the behaviour 
is more or less left up to the user agent. Silent failure and reusing 
DOM_QUOTA_ERROR are both reasonable solutions; another would be firing a 
custom exception.


> Is there an exciting exception that'd work better to tell the script 
> "the change failed because localStorage is currently immutable"?  If 
> not, is there any chance it could be added to the spec?

This is a similar case as being out of memory, or surviving a page fault, 
or having an I/O error. I suppose we could introduce exceptions for these 
cases; that would be something I'd defer to Simon and the Web DOM Core 
spec.


> Obviously only browser vendors that share WebKit's philosophy on 
> localStorage's "guarantee" of persistence would actually use this, but I 
> think it'd be far better than the current behavior.

I don't think this would be specific to localStorage.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'