How to see available options for homebrew formula install?

Question

I'm reading this stack overflow answer

Mac user and getting WARNING: Nokogiri was built against LibXML version 2.7.8, but has dynamically loaded 2.7.3

and I just want to know where they learned about the --with-xml2-config option in

brew install libxml2 --with-xml2-config

so that I can verify I really want to use this option myself and so I can better solve problems with homebrew myself in the future.

How can I see a description of this specific option and, more generally, find out all the available options for a formula when using brew install?

I know brew info FORMULA gets me some stuff like that, but brew info libxml2 only lists the options --universal, --without-python, and --HEAD.

For more info, here is another stack overflow question that is similar to this one but different: How can i get more info about a brew formula before installing?

Answer 1

Use options first to check:

brew options libxml2

If this dose not satisfy you, edit the rb file directly, and do whatever you want to:

brew edit libxml2

Answer 2

you can often see available options in the .rb brew file. Open with your favorite text editor, they usually live here on MacOS:

/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/

you can apply arguments in the files too, like --enable-foo

these files don't usually contain "descriptions" however

Answer 3

brew install ignores any options it does not recognize. --with-xml2-config is not a real option of the libxml2 formula; it just gets ignored.