Handlers

Via Planet PHP I stumbled across this article decrying Singletons. It's not a new argument, really, but one of the comments pointed me toward a Google Tech Talk video entitled "Global State and Singletons". To be honest I don't agree with everything said in either the article or the video, but both are spot on about the problems of global state, something I've lamented before in relation to testing.

That is especially relevant now, as we consider the question of Handlers in Drupal. Why? Because the most controvercial part so far, the environment variable, is designed to address exactly this problem, a problem that is currently prevalent throughout all of Drupal.

Permit me to explain.

Some time ago, I posted an RFC for pluggable "system handlers". It generated a fair bit of feedback, nearly all of it positive. That was followed up with a presentation in Szeged, which generated even more positive feedback.

So what's happened since then? Well, a fair bit. There's working code, but there are still some key gotchas to sort out. That gives us a couple of options for how to proceed, for which I would like feedback, particularly from core developers and maintainers. (Dries, webchick, this means you! :-) )

Recently I've been talking up various ideas for pluggable subsystems in Drupal in IRC and the other usual haunts. Ideas have been percolating in my head, but so far I have been remiss in actually writing them down. Yesterday, however, I had an epiphany to solve the primary issue I was trying to work out, so I present a hopefully workable RFC (for real, not IETF version) for pluggable subsystems in Drupal.

I am posting this over to Planet PHP as well to invite commentary from those who aren't already embedded in the Drupal mindset. :-)

By now you may have heard the news from Paris that a unit testing framework has landed in Drupal core. A huge shout-out goes to everyone involved. I particularly want to note the work that's been put in by former GHOP students and members of the GHOP team. It's amazing to see how far some people have come in a short time, despite still having homework to do. :-)

The next step, of course, is to make Drupal itself fully-tested. That poses a number of challenges, particularly for unit tests. Because I'm sure others will be singing the (well-deserved) praises of the testing team, I want to take a moment to focus on that next step and one important approach: Testable APIs.