Verification

• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.

Provide a detailed description of the proposed feature

Currently, we rewrite all library install names to something like opt_prefix/library_install_name.basename.

Typically, these will be because the install name refers to a Cellar path, e.g., prefix/library_install_name.basename. The install name rewriting allows us to avoid unnecessary rebuilds of dependents with version/revision bumps.

This install name rewriting isn't needed when the install name starts with @rpath, because these will typically not hardcode a Cellar path reference that will need to be rebuilt on version/revision bumps.

Formulae should support some sort of DSL that makes the code in keg_relocate.rb skip rewriting an install name if it starts with @rpath.

What is the motivation for the feature?

Our rewriting of @rpath-prefixed install names breaks macdeployqt. See Homebrew/discussions#2823.

This is arguably an upstream bug, but convincing upstream to fix it is unlikely to succeed without a reproduction of the issue outside of Homebrew, and I don't think anyone has the time or energy to do this. Even if one had such a reproducer, it would likely still be rather difficult to convince upstream to fix this short of providing a patch.

Such a DSL could also replace a very old workaround in Rust:

  def post_install
    Dir["#{lib}/rustlib/**/*.dylib"].each do |dylib|
      chmod 0664, dylib
      MachO::Tools.change_dylib_id(dylib, "@rpath/#{File.basename(dylib)}")
      MachO.codesign!(dylib) if Hardware::CPU.arm?
      chmod 0444, dylib
    end
  end

How will the feature be relevant to at least 90% of Homebrew users?

It probably won't be, but it would likely be relevant to our users who use Qt, which form a non-negligible fraction of our user base.

What alternatives to the feature have been considered?

See alternatives described in this comment.