module Kernel

def require(path) # :doc:
  return gem_original_require(path) unless Gem.discover_gems_on_require
  RUBYGEMS_ACTIVATION_MONITOR.synchronize do
    path = File.path(path)
    # If +path+ belongs to a default gem, we activate it and then go straight
    # to normal require
    if spec = Gem.find_default_spec(path)
      name = spec.name
      next if Gem.loaded_specs[name]
      # Ensure -I beats a default gem
      resolved_path = begin
        rp = nil
        load_path_check_index = Gem.load_path_insert_index - Gem.activated_gem_paths
        Gem.suffixes.find do |s|
          $LOAD_PATH[0...load_path_check_index].find do |lp|
            if File.symlink? lp # for backward compatibility
              next
            end
            full_path = File.expand_path(File.join(lp, "#{path}#{s}"))
            rp = full_path if File.file?(full_path)
          end
        end
        rp
      end
      Kernel.send(:gem, name, Gem::Requirement.default_prerelease) unless
        resolved_path
      next
    end
    # If there are no unresolved deps, then we can use just try
    # normal require handle loading a gem from the rescue below.
    if Gem::Specification.unresolved_deps.empty?
      next
    end
    # If +path+ is for a gem that has already been loaded, don't
    # bother trying to find it in an unresolved gem, just go straight
    # to normal require.
    #--
    # TODO request access to the C implementation of this to speed up RubyGems
    if Gem::Specification.find_active_stub_by_path(path)
      next
    end
    # Attempt to find +path+ in any unresolved gems...
    found_specs = Gem::Specification.find_in_unresolved path
    # If there are no directly unresolved gems, then try and find +path+
    # in any gems that are available via the currently unresolved gems.
    # For example, given:
    #
    #   a => b => c => d
    #
    # If a and b are currently active with c being unresolved and d.rb is
    # requested, then find_in_unresolved_tree will find d.rb in d because
    # it's a dependency of c.
    #
    if found_specs.empty?
      found_specs = Gem::Specification.find_in_unresolved_tree path
      found_specs.each(&:activate)
    # We found +path+ directly in an unresolved gem. Now we figure out, of
    # the possible found specs, which one we should activate.
    else
      # Check that all the found specs are just different
      # versions of the same gem
      names = found_specs.map(&:name).uniq
      if names.size > 1
        raise Gem::LoadError, "#{path} found in multiple gems: #{names.join ", "}"
      end
      # Ok, now find a gem that has no conflicts, starting
      # at the highest version.
      valid = found_specs.find {|s| !s.has_conflicts? }
      unless valid
        le = Gem::LoadError.new "unable to find a version of '#{names.first}' to activate"
        le.name = names.first
        raise le
      end
      valid.activate
    end
  end
  begin
    gem_original_require(path)
  rescue LoadError => load_error
    if load_error.path == path &&
       RUBYGEMS_ACTIVATION_MONITOR.synchronize { Gem.try_activate(path) }
      return gem_original_require(path)
    end
    raise load_error
  end
end