brew/Library/Homebrew/dependency_collector.rb

require "dependency"
require "dependencies"
require "ld64_dependency"
require "requirement"
require "requirements"
require "set"

## A dependency is a formula that another formula needs to install.
## A requirement is something other than a formula that another formula
## needs to be present. This includes external language modules,
## command-line tools in the path, or any arbitrary predicate.
##
## The `depends_on` method in the formula DSL is used to declare
## dependencies and requirements.

# This class is used by `depends_on` in the formula DSL to turn dependency
# specifications into the proper kinds of dependencies and requirements.
class DependencyCollector
  # Define the languages that we can handle as external dependencies.
  LANGUAGE_MODULES = Set[
    :lua, :lua51, :perl, :python, :python3, :ruby
  ].freeze

  CACHE = {}

  def self.clear_cache
    CACHE.clear
  end

  attr_reader :deps, :requirements

  def initialize
    @deps = Dependencies.new
    @requirements = Requirements.new
  end

  def add(spec)
    case dep = fetch(spec)
    when Dependency
      @deps << dep
    when Requirement
      @requirements << dep
    end
    dep
  end

  def fetch(spec)
    CACHE.fetch(cache_key(spec)) { |key| CACHE[key] = build(spec) }
  end

  def cache_key(spec)
    if Resource === spec && spec.download_strategy == CurlDownloadStrategy
      File.extname(spec.url)
    else
      spec
    end
  end

  def build(spec)
    spec, tags = Hash === spec ? spec.first : spec
    parse_spec(spec, Array(tags))
  end

  private

  def parse_spec(spec, tags)
    case spec
    when String
      parse_string_spec(spec, tags)
    when Resource
      resource_dep(spec, tags)
    when Symbol
      parse_symbol_spec(spec, tags)
    when Requirement, Dependency
      spec
    when Class
      parse_class_spec(spec, tags)
    else
      raise TypeError, "Unsupported type #{spec.class.name} for #{spec.inspect}"
    end
  end

  def parse_string_spec(spec, tags)
    if HOMEBREW_TAP_FORMULA_REGEX === spec
      TapDependency.new(spec, tags)
    elsif tags.empty?
      Dependency.new(spec, tags)
    elsif (tag = tags.first) && LANGUAGE_MODULES.include?(tag)
      LanguageModuleRequirement.new(tag, spec, tags[1])
    else
      Dependency.new(spec, tags)
    end
  end

  def parse_symbol_spec(spec, tags)
    case spec
    when :x11        then X11Requirement.new(spec.to_s, tags)
    when :xcode      then XcodeRequirement.new(tags)
    when :macos      then MinimumMacOSRequirement.new(tags)
    when :mysql      then MysqlRequirement.new(tags)
    when :postgresql then PostgresqlRequirement.new(tags)
    when :gpg        then GPGRequirement.new(tags)
    when :fortran    then FortranRequirement.new(tags)
    when :mpi        then MPIRequirement.new(*tags)
    when :tex        then TeXRequirement.new(tags)
    when :arch       then ArchRequirement.new(tags)
    when :hg         then MercurialRequirement.new(tags)
    when :python     then PythonRequirement.new(tags)
    when :python3    then Python3Requirement.new(tags)
    when :java       then JavaRequirement.new(tags)
    when :rbenv      then RbenvRequirement.new(tags)
    when :ruby       then RubyRequirement.new(tags)
    when :osxfuse    then OsxfuseRequirement.new(tags)
    when :perl       then PerlRequirement.new(tags)
    when :tuntap     then TuntapRequirement.new(tags)
    when :ant        then ant_dep(spec, tags)
    when :apr        then AprRequirement.new(tags)
    when :emacs      then EmacsRequirement.new(tags)
    # Tiger's ld is too old to properly link some software
    when :ld64       then LD64Dependency.new if MacOS.version < :leopard
    # Tiger doesn't ship expat in /usr/lib
    when :expat      then Dependency.new("expat", tag) if MacOS.version < :leopard
    when :python2
      PythonRequirement.new(tags)
    else
      raise ArgumentError, "Unsupported special dependency #{spec.inspect}"
    end
  end

  def parse_class_spec(spec, tags)
    if spec < Requirement
      spec.new(tags)
    else
      raise TypeError, "#{spec.inspect} is not a Requirement subclass"
    end
  end

  def ant_dep(spec, tags)
    if MacOS.version >= :mavericks
      Dependency.new(spec.to_s, tags)
    end
  end

  def resource_dep(spec, tags)
    tags << :build
    strategy = spec.download_strategy

    case
    when strategy <= CurlDownloadStrategy
      parse_url_spec(spec.url, tags)
    when strategy <= GitDownloadStrategy
      GitRequirement.new(tags)
    when strategy <= MercurialDownloadStrategy
      MercurialRequirement.new(tags)
    when strategy <= FossilDownloadStrategy
      Dependency.new("fossil", tags)
    when strategy <= BazaarDownloadStrategy
      Dependency.new("bazaar", tags)
    when strategy <= CVSDownloadStrategy
      Dependency.new("cvs", tags) if MacOS.version >= :mavericks || !MacOS::Xcode.provides_cvs?
    when strategy < AbstractDownloadStrategy
      # allow unknown strategies to pass through
    else
      raise TypeError,
        "#{strategy.inspect} is not an AbstractDownloadStrategy subclass"
    end
  end

  def parse_url_spec(url, tags)
    case File.extname(url)
    when ".xz"  then Dependency.new("xz", tags)
    when ".lha", ".lzh" then Dependency.new("lha", tags)
    when ".lz"  then Dependency.new("lzip", tags)
    when ".rar" then Dependency.new("unrar", tags)
    when ".7z"  then Dependency.new("p7zip", tags)
    end
  end
end