Specifying Swift and/or Xcode versions in a formula

[rgoldberg]

Output of brew config

n/a

Output of brew doctor

n/a

Description of issue

The mas formula requires Swift 6.2+ to build.

Normally, that is provided by Xcode, but Swift 6.2 is only included with Xcode 26+, which can only run on macOS 15.6, so cannot be used by Homebrew Core to build for x86_64 or macOS 14.

The mas formula currently builds for x86_64 & macOS 14 using the Homebrew Core swift formula. The mas formula currently includes:

depends_on xcode: ["16.0", :build]

uses_from_macos "swift" => :build, since: :sequoia # swift 6.2+

Xcode 16.0 cannot build Swift 6.2, but macOS 14 can now build without Xcode.

It's best to build with Swift from Xcode whenever that can be used instead of with the Swift from the Homebrew Core swift formula.

If I delete depends_on xcode: ["16.0", :build], will everything still build fine, using Swift from Xcode on macOS 15 & 26, while using Swift from Homebrew Core on macOS 14? Or is some depends_on xcode statement still necessary?

If such a statement is necessary, I shouldn't use depends_on xcode: ["16.0", :build], because 16.0 is useless. But would depends_on xcode: ["26.0", :build] preclude macOS 14 from building mas, because Xcode 26 cannot be installed on macOS 14?

[p-linnane]

If I delete depends_on xcode: ["16.0", :build], will everything still build fine, using Swift from Xcode on macOS 15 & 26, while using Swift from Homebrew Core on macOS 14? Or is some depends_on xcode statement still necessary?

Without depends_on xcode your formula will just fail to build if Xcode is needed and the system doesn't have it installed.

If such a statement is necessary, I shouldn't use depends_on xcode: ["16.0", :build], because 16.0 is useless. But would depends_on xcode: ["26.0", :build] preclude macOS 14 from building mas, because Xcode 26 cannot be installed on macOS 14?

You'll probably want to do something like

on_sequoia :or_newer do
  depends_on Xcode: ["26.0", :build]
end

on_sonoma do
  depends_on swift => :build
end

No guarantee that will actually work, but that's my best guess at how you can do what you want if I'm understanding you correctly.

[rgoldberg]

Thanks. I'll try that.