"Chad" <[email protected]> wrote in message
news:[email protected]...
> On Sun, Apr 4, 2010 at 1:43 PM, Happy-melon <[email protected]> wrote:
>> As Roan says, a Message object essentially deprecates the (IMO pig-ugly)
>> Status class, which is used erratically throughout the codebase as
>> essentially a way to bundle up a message key, some parameters, and a
>> success
>> flag without converting to String too soon. Status has always struck me
>> as
>> an unpleasant implementation: processes should throw exceptions on fatal
>> errors, return messages on non-catastrophic problems, and bool true on
>> success.
>
> As opposed to returning a single class which can handle errors, warnings
> and OK statuses just fine? I really don't know why people don't like the
> Status class, I'm trying to use it *more* in the new-installer, rather
> than
> returning weird mixtures of booleans, strings and exceptions.
>
> -Chad
It's pretty rare for 'error', 'warning', and 'ok' to all have independent
meanings in MW. I can see the installer being an exception; but in general,
we don't implement an "I did your action but this problem meant it's not
entirely as you would expect" result; we fail and give the user an option to
try again; that's not really any different to an error.
The real distinction is between errors that *preclude* a repeat attempt, and
those that just indicate a failure this time around or with that particular
set of data. Errors like read-only-wiki or not-authorised should be handled
with exceptions which are caught high up in the call stack, probably at the
level of Wiki.php; the message you get if you try to edit a page on a
read-only wiki needn't be much different to trying to change userrights on a
read-only wiki. Ditto for permissions errors, and anything else that leads
to a 'dead end' error screen. All we're achieving with our
if(wfReadOnly()){global $wgOut; $wgOut->readOnlyPage(); return false; } is
to terminate call stacks early; that's exactly what exceptions should be
used for. We just need a wfAssertWritable() function which throws a
MWReadOnlyException on a locked wiki.
Any error which should be handled by redisplaying the form unquestionably
needs to be accompanied by an informative error message, and conversely the
"Your foo has been barred" success message is either going to be
state-independent ("we successfully made the requested changes to your Foo")
or will have done object instantiation ("based on your input, we have
created a shiny new Foo"), which you'd keep in a member variable anyway. As
such, every success needs no data returned from it, every transient error
needs a message associated with it, and every permanent error should be
handled by exceptions. Why complicate things with a wrapper class to convey
information you can work out from context anyway?
--HM
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