David vs Goliath, or how to keep custom file associations after each Xcode update

Updating Xcode/macOS usually resets file type associations and requires reassigning default program for them to some other editor that is not as slow and inflexible as Xcode. I personally prefer Sublime Text and would really like Apple to stop constantly messing up my configuration.

lsregister

Using tips from the article lsregister: How Files Are Handled in Mac OS X we can automate assigning Sublime Text for files we need.

Let’s make a soft link to lsregister for convenience:

ln -s /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister

We can now dump Launch Service database, but since it takes some time, let’s dump it to a text file first:

./lsregister -dump > lsregister.txt  

Now, we can determine which programs are associated with specific file types:

cat lsregister.txt | grep -E 'bundle id:|claimed UTIs:'

and for Xcode specifically:

$ cat lsregister.txt | grep -E 'bundle id:|claimed UTIs:' | grep 'Xcode (' -A1
bundle id:                  Xcode (0x80c)
claimed UTIs:               public.shell-script, public.bash-script, public.yaml, public.json, ...

In order to see what Uniform Type Identifier (UTI) corresponds to a given filename extension, we can use metadata list utility mdls:

$ mdls Makefile
_kMDItemDisplayNameWithExtensions  = "Makefile"
...
kMDItemContentType                 = "public.make-source"
kMDItemContentTypeTree             = (
    "public.make-source",
    "public.script",
    "public.source-code",
    "public.plain-text",
    "public.text",
    "public.data",
    "public.item",
    "public.content"
)
...

or specifically for kMDItemContentType:

$ mdls -name kMDItemContentType Makefile
kMDItemContentType = "public.make-source"

Unregister

The article also suggests that one can unregister Xcode, but it seems not possible anymore:

$ ./lsregister -u /Developer/Applications/Xcode.app
failed to scan /Developer/Applications/Xcode.app: -10814
 from spotlight

defaults read

Since the article was published in 2012, the plist has been moved, so instead of old ~/Library/Preferences/com.apple.LaunchServices.plist one should use ~/Library/Preferences/com.apple.LaunchServices/com.apple.launchservices.secure.plist.

Let’s see what we have there:

$ defaults read ~/Library/Preferences/com.apple.LaunchServices/com.apple.LaunchServices.secure.plist
{
    LSHandlers =     (
                {
            LSHandlerPreferredVersions =             {
                LSHandlerRoleAll = "-";
            };
            LSHandlerRoleAll = "us.zoom.xos";
            LSHandlerURLScheme = zoomphonecall;
        },
...

defaults write

Let’s change default application for Makefile:

$ defaults write com.apple.LaunchServices/com.apple.LaunchServices.secure LSHandlers \
   -array-add '{LSHandlerContentType=public.make-source;LSHandlerRoleAll=com.sublimetext.4;}'

$ defaults read com.apple.LaunchServices/com.apple.LaunchServices.secure | tail -5
            LSHandlerContentType = "public.make-source";
            LSHandlerRoleAll = "com.sublimetext.4";
        }
    );
}

Now we have to restart macOS, since relaunching Finder and running the following command does not help:

./lsregister -kill -r -domain local -domain system -domain user

Test

The following commands should open Sublime Text instead of Xcode.

touch Makefile
open Makefile

Now we can make a script for opening all common files via our editor.

TBC