untap: require CaskLoader

[capruxel]

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While trying to remove kegworks-app/kegworks, I found that brew untap fails when the tap has an installed cask.

Reproduction

On the current main branch:

brew tap kegworks-app/kegworks
brew install --cask kegworks-app/kegworks/sikarugir
brew untap kegworks-app/kegworks

The final command fails with:

Error: uninitialized constant Cask::CaskLoader
/opt/homebrew/Library/Homebrew/cmd/untap.rb:132:in 'block in Homebrew::Cmd::Untap#installed_casks_for'
/opt/homebrew/Library/Homebrew/cmd/untap.rb:128:in 'Array#each'
/opt/homebrew/Library/Homebrew/cmd/untap.rb:128:in 'Enumerable#filter_map'
/opt/homebrew/Library/Homebrew/cmd/untap.rb:128:in 'Homebrew::Cmd::Untap#installed_casks_for'

From what I can tell, installed_casks_for calls Cask::CaskLoader.load(...) while checking installed casks, but does not load cask/cask_loader before using it.

This change loads cask/cask_loader inside installed_casks_for, where Cask::CaskLoader is used, and updates the existing untap integration test. The test now installs a cask from the test tap and uses brew untap --force in a fresh process to exercise the same installed-cask path without requiring interactive confirmation.

This may be related to the recent Cask lazy-loading changes in #23560. Similar Cask::CaskLoader loading regressions were addressed in #23566 and #23587.

Testing

I verified the regression with a red/green test cycle:

• without require "cask/cask_loader", the integration test fails with uninitialized constant Cask::CaskLoader;
• with the require restored, the test passes.

I also ran:

./bin/brew tests --only=cmd/untap
./bin/brew lgtm --online

Both completed successfully.

AI/LLM disclosure

ChatGPT (GPT-5.6 Sol) was used to assist with investigating the failure, reviewing related Homebrew changes, understanding the contribution process, and developing the regression test. I reviewed the code and prose myself and reproduced and tested the changes locally.

[MikeMcQuaid]

Thanks!