Allan Odgaard on file type detection in TextMate

Created 10/18/2007, updated 3/12/20242 minute read

I’ve never been able to get TextMate to reliably detect Ruby, Rails and RSpec files. Allan Odgaard, the author of TextMate, explains here how to bend the system to your will.

I think there’s something obviously wrong with the design when it takes this much effort to get file extensions correctly mapped, but I also suspect that you’re not about to see the system overhauled (there are too many bundles out there which use it); at least there is a workaround, no matter unnecessarily complicated it may seem.

If you want, you can start by reviewing your manual file type bindings (optional):

defaults read com.macromates.textmate OakLanguageFileBindings

Your manual bindings are almost certainly the cause of the problem, so ensure that TextMate is not running and delete them all:

defaults delete com.macromates.textmate OakLanguageFileBindings

Now open up a Ruby file in TextMate and manually set its type to Ruby in the language pop-up:

mate /tmp/file.rb

Quit TextMate and re-check your manual bindings again; the should be empty:

defaults read com.macromates.textmate OakLanguageFileBindings

Now fire up TextMate and go to the "Bundles" menu, "Bundle Editor" submenu, "Edit Languages" item, and make this change in the Rails language definition:

   fileTypes = ( 'rxml' );

Should become:

   fileTypes = ( 'rxml', 'rb' );

And in the Ruby language definition:

   fileTypes = ( 'rb', 'rbx', 'rjs', 'Rakefile', 'rake', 'cgi', 'fcgi', 'gemspec' );

Should become:

   fileTypes = ( 'rbx', 'rjs', 'Rakefile', 'rake', 'cgi', 'fcgi', 'gemspec' );

Now when you open .rb files they should default to Rails as their "language", and _spec.rb files should default to RSpec.

(These instructions are basically copied directly from Allan’s weblog; I include them here to demonstrate my point about the complexity of this operation.)

Now all you need to do is remember never to touch the Language pop-up again. The problem is that all your plain Ruby files will now be identified as "Rails", even when they have nothing to do with Rails (of course, Ruby is much more than just Rails). If you fall into the trap of toggling the language pop-up back to "Ruby" for such a file then you’ve blown it and will have delete your manual language bindings again.

What’s the ideal solution to this quagmire? Evidently the key piece is a method for choosing between ambiguous options (where .rb can be Rails or Ruby). What would be the best way to do this? Writing it to the files resource fork? (not so good on a multi-user system where many different users may edit the same file.) Keeping the type information in per-user, centralized store? (in your ~/Library/Application Support/ directory.) Allowing regular expressions based on the full path of the file, not just its extension? (in other words, matching against paths like .+/app/models/.+\.rb; that’s not the actual regex I would use but this darn wiki markup I’m using doesn’t allow me to type square brackets!)

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