I started a small discussion on the newsgroups the other day wondering about the numbers of API changes that had landed on trunk since 1.9.0. It was a short discussion, maybe partly because all I had to go on were the vague metrics that mercurial could give me. It also evolved a little into a discussion of how add-on developers we’re meant to find out about API changes. It’s true that as developers we are getting better at trying to announce our changes as much as possible, but inevitably we miss some, and if you don’t track the announcements what then?

Yesterday on IRC ted jokingly made the comment that I could use the idl parser than bsmedberg wrote in python a short time ago to find out more about the API changes. I’ve been hard pressed on other work lately so it wasn’t long before the prospect of knocking together a little side project had me too interested to do anything else. In a short space of time I had something that could parse all the in-tree idl files into a sqlite database that I could then query. It wasn’t long after that that I got a small web app written to display the content of the database, but I spent some more time today getting it a bit more useful before I showed it to the rest of the world.

So here it is, the API viewer. You can look at any interface in any of the platform versions that I’ve bothered to scan. And here is the more interesting bit, you can compare two platforms to see what interfaces changed. Not happy there? Well you can also compare an interface in different platform versions in a sort of diff like display.

I should note that it is only indexing the core and Firefox interfaces for now, and it’s close to indexing all of the idl files from the sources, many of which don’t make it into the final build (which makes life interesting as it turns out some of them are invalid xpidl!). So you can’t trust that interfaces you find are necessarily useful etc.

The web app is really a prototype right now. Navigation is probably a bit clunky and it’ll need more work to be really useful but I wondered what other people thought of it. So what do you think? Is it useful? What other interesting information might we be able to grab automatically like this?

Update: I’ve added details of the current trunk, 1.9.1b2pre as of today so you can see what changes are coming since the last beta. Not sure how often I’ll keep that up to date though.