validate_dependencies

# File lib/rubygems/specification.rb, line 2919
  def validate_dependencies # :nodoc:
    # NOTE: see REFACTOR note in Gem::Dependency about types - this might be brittle
    seen = Gem::Dependency::TYPES.inject({}) { |types, type| types.merge({ type => {}}) }

    error_messages = []
    warning_messages = []
    dependencies.each do |dep|
      if prev = seen[dep.type][dep.name] then
        error_messages << duplicate dependency on #{dep}, (#{prev.requirement}) use:    add_#{dep.type}_dependency '#{dep.name}', '#{dep.requirement}', '#{prev.requirement}'
      end

      seen[dep.type][dep.name] = dep

      prerelease_dep = dep.requirements_list.any? do |req|
        Gem::Requirement.new(req).prerelease?
      end

      warning_messages << "prerelease dependency on #{dep} is not recommended" if
        prerelease_dep && !version.prerelease?

      overly_strict = dep.requirement.requirements.length == 1 &&
        dep.requirement.requirements.any? do |op, version|
          op == '~>' and
            not version.prerelease? and
            version.segments.length > 2 and
            version.segments.first != 0
        end

      if overly_strict then
        _, dep_version = dep.requirement.requirements.first

        base = dep_version.segments.first 2

        warning_messages << pessimistic dependency on #{dep} may be overly strict  if #{dep.name} is semantically versioned, use:    add_#{dep.type}_dependency '#{dep.name}', '~> #{base.join '.'}', '>= #{dep_version}'
      end

      open_ended = dep.requirement.requirements.all? do |op, version|
        not version.prerelease? and (op == '>' or op == '>=')
      end

      if open_ended then
        op, dep_version = dep.requirement.requirements.first

        base = dep_version.segments.first 2

        bugfix = if op == '>' then
                   ", '> #{dep_version}'"
                 elsif op == '>=' and base != dep_version.segments then
                   ", '>= #{dep_version}'"
                 end

        warning_messages << open-ended dependency on #{dep} is not recommended  if #{dep.name} is semantically versioned, use:    add_#{dep.type}_dependency '#{dep.name}', '~> #{base.join '.'}'#{bugfix}
      end
    end
    if error_messages.any?
      raise Gem::InvalidSpecificationException, error_messages.join
    end
    if warning_messages.any?
      warning_messages.each { |warning_message| warning warning_message }
    end
  end