How do I test changes to a formula?

[SSteve]

I'm getting an error ("ArgumentError: comparison of String with 8 failed") building llvm on MacOS Mojave. I know Mojave isn't supported, so I'm trying to fix it myself. Installing with debug and verbose flags helped me track it down to this line. I think it should be compat_version = Integer(xcode_version) < 8 ? "1" : "2". I'm pretty sure changes I make to llvm.rb before installing are overwritten. How can I run the install with my version of the formula?

Building llvm takes hours so there's a long time between starting the install and getting the error message. Is there any way to keep the build products and re-run the install with them?

[carlocab]

Oops, sorry for that. This should be fixed by Homebrew/homebrew-core#91436.

As for your question: you should be able to just do brew edit llvm, make your changes, and then do brew install llvm.

[carlocab]

This should be fixed now. Do brew update to pull in the fix.

[SSteve]

It worked great, thanks!