New subject: New methods to use when checking if a title is part of a namespace

22 Nov 2011

I've added a few lightly abstract methods to replace some of the direct  
comparisons we make related to namespaces.

When you want to see if a title is part of a namespace, instead of writing  
this:
$title->getNamespace() == NS_USER

You can now (or rather, if you don't have compat issues, PLEASE DO use it):
$title->inNamespace( NS_USER );

When you need to make a test if a page is part of a subject or a talk eg  
either User or User_talk instead of something verbose like:
$title->getNamespace() == NS_USER || $title->getNamespace() == NS_USER_TALK

Please use:
$title->hasSubjectNamespace( NS_USER );

hasSubjectNamespace will return true if the title's namespace's subject  
namespace matches the subject namespace of the namespace you pass in.

If you're writing verbose code testing if a title is in any of a number of  
namespaces by using in_array you can use inNamespaces (note the 's'):
$title->inNamespace( NS_USER, NS_TEMPLATE );

To be honest, I don't have any good example use cases on hand of where you  
would use that, but I didn't want the lack of that functionality and the  
simplicity of in_array to be a valid rationale in not making use of these  
abstract interfaces to namespace info.

Likewise there are two MWNamespace methods to match. MWNamespace::equals  
and MWNamespace::subjectEquals.

And I DO encourage people making $ns == NS_???? comparisons to use  
MWNamespace::equals( $ns, NS_???? ) instead. Even though technically right  
now MWNamespace::equals is in fact `return $ns1 == $ns2;`.

This is a little relevant to the "MediaWiki should use a reservation  
system for namespaces" bug:
https://bugzilla.wikimedia.org/show_bug.cgi?id=31063

The idea is essentially to drop our practice of passing around integers  
and instead start passing around keys like "USER", "SMW_PROPERTY",
etc...  
MediaWiki would have a namespace registration system where when given a  
new key it would reserve a new namespace number for that key.
Instead of extensions being forced to declare what integers they are going  
to use and coordinate with other extension developers so that extensions  
don't conflict they can instead just make a call to MediaWiki declaring a  
string based key like "SMW_PROPERTY" which should not be confusable with  
another extension and then MediaWiki will register an integer in the  
database for that namespace and reserve it for use with that key. This  
also has the benefit that if you install an extension then uninstall it,  
you shouldn't lose the contents of the namespace, and when you re-install  
it'll start working again without issues like conflicts with titles  
created in NS_MAIN that match the prefix used. Theoretically changing the  
content language of your wiki from say 'fr' to 'it' could be made in such 

a way that MediaWiki won't break existing links and instead the old  
i18n'ed NS will end up as an alias.
The idea also fits in with another bug asking for a namespace manager ui.  
If we switch to a namespace registration system it will be much easier to  
create an administrative ui for this.

Having these abstract interfaces for namespace comparison around will mean  
that in the future if we do in fact start passing around things like  
"USER" instead of integers, there should be no issue of bugs cropping up  
if some code happens to come together and for an unfortunate reason you  
happen to have both "USER" and `2` passed from different sources. Making  
use of Title::inNamespace and MWNamespace::equals will ensure that even if  
you have "USER" and `2` they will be considered equivalent. Unlike what  
would happen if you'd used == directly.

-- 
~Daniel Friesen (Dantman, Nadir-Seen-Fire) [http://daniel.friesen.name]