formula: make prefix usually return opt_prefix.

Return `opt_prefix` if it exists and `prefix` is not called from within
the same formula's `install` or `post_install` methods. Otherwise, fall
back to the existing functionality.

This avoids the need to use `opt_prefix` etc. everywhere and generally
means we don't expose an implementation detail (i.e. the full Cellar
path) to dependents that have a habit of hard-coding it.

1 files changed, 1 insertions, 1 deletions

diff --git a/Library/Homebrew/cmd/--prefix.rb b/Library/Homebrew/cmd/--prefix.rb
index c59830833..f6e7d2ee2 100644
--- a/Library/Homebrew/cmd/--prefix.rb
+++ b/Library/Homebrew/cmd/--prefix.rb
@@ -11,7 +11,7 @@ module Homebrew
     if ARGV.named.empty?
       puts HOMEBREW_PREFIX
     else
-      puts ARGV.resolved_formulae.map { |f| f.opt_prefix.exist? ? f.opt_prefix : f.installed_prefix }
+      puts ARGV.resolved_formulae.map(&:installed_prefix)
     end
   end
 end