How to add an alternative option to formula (or create cast) that compiles program with GUI support?

[munro]

Output of brew config

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Output of brew doctor

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Description of issue

hey all, I want to add the GUI version of SWI-Prolog to homebrew, but I have some barriers I'm not sure how to overcome.

The official GUI built version for macOS is unsigned, so I can't add it as a cask¹, at least not until it's signed², if the devs will even do that.

I still would love to add it, because the gtrace is really nice, and so is homebrew. The core package essentially just needs to have the GUI build flags turned on³, and deps added⁴.

So I'm kind of wondering what to do, thoughts lingering:

• should it be cask? thinking no, from what I can tell, casks cannot be "built" like formulas. Me personally, I don't need the /Applications/SWI-Prolog.app, I just need gtrace. to work in the terminal swipl program.
• should this be built as an alternative formula? I see in docs Homebrew/core cannot have :optional dependencies.
• should I it just have _X=on by default? not sure if that's acceptable for everyone though...
• it requires xquartz, so if it's a formula, it can't depend on a cask?
• can I build with X enabled using only formulas? I'm not sure how the x deps work... but if that was the case then I can keep it as a formula, and caveat that the xquartz cast needs to be installed so gtrace works (this seems the most ideal). But not sure what build packages are need to compile with X extensions enabled.

I know I can create my own tap, but I was hoping there's some solution using the official swi-prolog repos/downloads to include into offical homebrew core/cask, so that others can use and it with more trust.

any help/thoughts/support is appreciated! thanks!

Footnotes

1. https://github.com/Homebrew/homebrew-cask/pull/176803 ↩

2. https://github.com/SWI-Prolog/swipl-devel/issues/1288 ↩

3. -DSWIPL_PACKAGES_X=ON https://github.com/Homebrew/homebrew-core/blob/9da60e3fc1c4de3160e8695ac32be3321b324506/Formula/s/swi-prolog.rb#L50 ↩

4. I believe freetype, libx11, :cask xquartz ↩

[SMillerDev]

This sounds like it would massively increase the dependency tree, so it doesn't seem like something the Homebrew/core formula should do. You can easily maintain your own cask or a formula for it in your own tap like you mentioned. In the end the only person who needs to trust it is you, since I've never seen a request like this before.