Load casks from the internal API

[Rylan12]

This PR primarily enables installing casks from the internal API via HOMEBREW_REALLY_USE_INTERNAL_API. It's essentially the exact same implementation as for Formulae, and seems to work from preliminary local testing.

In addition, I've added a new #loaded_from_internal_api? method to Formula and Cask that gates some minor functionality differences between the internal and non-internal APIs.

These two changes are somewhat coupled together, which is why I've done it in a single PR. I've split up the commits into a formula commit and a cask commit, which may make reviewing a bit easier. If it's still too much, I can spend more time getting them split up.

[Copilot]

Pull request overview

Enables loading/installing casks from the internal API when HOMEBREW_REALLY_USE_INTERNAL_API is set, mirroring the existing formula internal-API path and tracking whether a package was loaded from the internal API for small behavioral differences (e.g., messaging and gating some hash generation).

Changes:

• Add loaded_from_internal_api? to Formula and Cask and persist loaded_from_internal_api into install receipts/tabs.
• Teach cask API loader and internal API cache to build CaskStruct objects from the internal API (including caching tap git head).
• Update tab/cask tab string output and expand test coverage + fixtures for the new receipt field.

Reviewed changes

Copilot reviewed 17 out of 18 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Library/Homebrew/test/tab_spec.rb	Adds assertions/matcher and new Tab#to_s expectations for internal API installs.
Library/Homebrew/test/support/fixtures/receipt.json	Adds loaded_from_internal_api to receipt fixture.
Library/Homebrew/test/support/fixtures/cask_receipt.json	Adds loaded_from_internal_api to cask receipt fixture.
Library/Homebrew/test/formulary_spec.rb	Asserts formulae loaded from (public) API are not marked as internal.
Library/Homebrew/test/formula_spec.rb	Adds Formula#specified_path test for internal API path behavior.
Library/Homebrew/test/cask/tab_spec.rb	Updates cask tab serialization and string output expectations for internal API installs.
Library/Homebrew/test/cask/info_spec.rb	Adds brew info output coverage for an internally-loaded cask install receipt.
Library/Homebrew/test/cask/cask_spec.rb	Asserts casks loaded from (public) API are not marked as internal.
Library/Homebrew/test/cask/cask_loader/from_api_loader_spec.rb	Adds expectation for loaded_from_internal_api? == false in API loader spec.
Library/Homebrew/tab.rb	Persists and prints loaded_from_internal_api in tabs/receipts.
Library/Homebrew/sorbet/rbi/dsl/formula.rbi	Adds RBI for Formula#loaded_from_internal_api?.
Library/Homebrew/formulary.rb	Propagates an internal_api: flag into API-loaded formula classes.
Library/Homebrew/formula_installer.rb	Writes loaded_from_internal_api into the install tab during bottle pours.
Library/Homebrew/formula.rb	Adds loaded_from_internal_api?, adjusts specified_path, and gates to_hash_with_variations.
Library/Homebrew/cask/tab.rb	Persists and prints loaded_from_internal_api in cask tabs.
Library/Homebrew/cask/cask_loader.rb	Adds internal-API struct loading path and passes internal flag into cask instances.
Library/Homebrew/cask/cask.rb	Adds loaded_from_internal_api? and gates to_hash_with_variations.
Library/Homebrew/api/internal.rb	Adds internal cask struct caching and exposes internal cask tap git head.

Files not reviewed (1)

• Library/Homebrew/sorbet/rbi/dsl/formula.rbi: Language not supported

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Rylan12]

Going to stop for the night, but the main to-do item is verifying that we can read the internal API JSON files in .metadata directories for installed casks.

I haven't tested yet, but I believe this will cause issues with running brew install --cask foo while using the internal API, and then brew uninstall foo while not using the internal API.

Edit: uninstall doesn't seem to work at all right now, so that's something to work on

[MikeMcQuaid]

Looks good when working!

Is the plan still that we will eventually merge the formula and cask files?