Finder File Extension Fun

Now, in the Finder, we can easily change the extension from one unregistered type (in this case, .bar) to another (let's try .baz). No problem there. Easy to switch back as well.

But things get decidedly more interesting with registered extensions. Case in point, try renaming Foo.bar to Foo.txt. You see, .txt is registered to TextEdit. Previously, the Finder allowed the name change without challenge. Now, however, you'll face a warning dialog. Are you sure you want to do this? Go ahead -- you'll find the file is now named Foo.txt. But more than the name has changed: the file gains TextEdit's text document icon, and a "Plain text document" type description.

And here's the "feature". Try to rename Foo.txt back to Foo.bar.

You can't.

Oh sure, the Finder will list the file's name as Foo.bar again, but the Finder is lying to you. Really, the file's name is now Foo.bar.txt. You can get the Finder to give up its pretenses by using Get Info on the file, and opening the little Name and Extension inspector panel.

I don't understand the mind games Finder X is playing with me here, but I gather it's some lame work-around to try to hide the broken behavior that embody file extensions. Anyway, you can turn off these mind games in Finder's preferences: turn on Always show file extensions.

By the way, initially I was going to file this entry under Bugs, but I decided it really belongs under Suck. The difference is that bugs are mostly nonintentional or at least limited in scope. However, the broken behavior of file extensions is endemic to Mac OS X, and was a conscious design decision. Systemic brokenness earns Suck. Congratulations, Mac OS X.

Update: John Gruber (whose last name contains a statistically average vowel/consonant ratio for English monikers) comments.

Wednesday, June 04, 2003
12:00 AM