Nathan Kleyn

I recently had a bit of fun after upgrading to Homebrew v1.9.0, so wanted to write a quick PSA for others who may hit the same issue.

Homebrew >= v1.9.0 has a breaking change to brew link --force:

brew link --force will not link software already provided by macOS.

That is, this change means that Homebrew will no longer allow brew link to override anything MacOS already ships with.

So for example, if you used Homebrew to install a recent version of Ruby, before v1.9.0 Homebrew’s version would’ve been in your path — now the MacOS system version will be in your path:

$ ruby -v
ruby 2.3.7p456 (2018-03-28 revision 63024) [universal.x86_64-darwin18]
$ /usr/local/opt/ruby/bin/ruby -v
ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-darwin18]

If you try to brew link it, Homebrew will tell you why it’s refusing to, and give you a snippet of script for prepending it to your PATH in your chosen shell (in my case, fish):

 $ brew link --force ruby
Warning: Refusing to link macOS-provided software: ruby
If you need to have ruby first in your PATH run:
  echo 'set -g fish_user_paths "/usr/local/opt/ruby/bin" $fish_user_paths' >> ~/.config/fish/config.fish

For compilers to find ruby you may need to set:
  set -gx LDFLAGS "-L/usr/local/opt/ruby/lib"
  set -gx CPPFLAGS "-I/usr/local/opt/ruby/include"

For pkg-config to find ruby you may need to set:
  set -gx PKG_CONFIG_PATH "/usr/local/opt/ruby/lib/pkgconfig"

You can also see this information for any given package by running brew info <package>.

The upgrade to v1.9.0 does not give any warning about this — the change is effectively silent — so beware of scripts depending any binaries that clash with MacOS provided ones being in your default system PATH!