The fix_wrapper.rb hook does not honor the env_shebang option

[ryotakatsuki]

After installing a gem through "gem install mygem --env-shebang", after the wrapper gets overwritten by the fix-wrapper.rb hook, the shebang is overwritten as @env_shebang is not defined in RubyGemsBundlerInstaller. It should take into account the configuration passed in gem.

[mpapis]

please point me to some documentation or source code of rubygems that handles it

[ryotakatsuki]

Sorry for the lack of detail.

In rubygems (rubygems/installer.rb):

def shebang(bin_file_name)
   ruby_name = Gem::ConfigMap[:ruby_install_name] if @env_shebang
   ...
   if not ruby_name then
     "#!#{Gem.ruby}#{opts}"
   elsif opts then
     "#!/bin/sh\n'exec' #{ruby_name.dump} '-x' \"$0\" \"$@\"\n#{shebang}"
   else
     # Create a plain shebang line.
     "#!#{@env_path} #{ruby_name}"
   end
 end

Where the @env_shebang variable comes from (also in installer.rb)

def process_options
    @options = {
      :bin_dir      => nil,
      :env_shebang  => false,
      :exec_format  => false,
      :force        => false,
      :install_dir  => Gem.dir,
    }.merge options
    @env_shebang         = options[:env_shebang]
    ...
end

And is defined when launching the gem install/upgrade command with --env-shebang or -E flags.

Then, after installing the gems, the hooks are executed. In fix_wrapper.rb:

module Gem
  post_install do |inst|
    RubyGemsBundlerInstaller.bundler_generate_bin(inst)
  end
end

Which calls bundler_generate_bin to rewrite the wrapper (in rubygems-bundler/rubygems_bundler_installer.rb). It uses a modified version of the shebang proc:

def self.shebang(inst, bin_file_name)
   ruby_name = Gem::ConfigMap[:ruby_install_name] if @env_shebang 
   ...
   if not ruby_name then
      "#!#{Gem.ruby}#{opts}"
   ...
   end
   ...
end

In the above proc, as @env_shebang is never defined, the condition does not match and hence, the shebang is written as "#!#{Gem.ruby}#{opts}" (regardless of if @env_shebang was true in the rubygems portion of the execution).

I believe a possible patch would be using:

def self.shebang(inst, bin_file_name)
   ruby_name = Gem::ConfigMap[:ruby_install_name] if inst.options[@env_shebang]
   ...
end

Using inst.options to access the passed in options but I have not verified it.