path: root/lib/psych.rb

require 'psych.so'
require 'psych/nodes'
require 'psych/streaming'
require 'psych/visitors'
require 'psych/handler'
require 'psych/tree_builder'
require 'psych/parser'
require 'psych/omap'
require 'psych/set'
require 'psych/coder'
require 'psych/core_ext'
require 'psych/deprecated'
require 'psych/stream'
require 'psych/json/tree_builder'
require 'psych/json/stream'
require 'psych/handlers/document_stream'
require 'psych/class_loader'

###
# = Overview
#
# Psych is a YAML parser and emitter.
# Psych leverages libyaml [Home page: http://pyyaml.org/wiki/LibYAML]
# or [Git repo: https://github.com/zerotao/libyaml] for its YAML parsing
# and emitting capabilities. In addition to wrapping libyaml, Psych also
# knows how to serialize and de-serialize most Ruby objects to and from
# the YAML format.
#
# = I NEED TO PARSE OR EMIT YAML RIGHT NOW!
#
#   # Parse some YAML
#   Psych.load("--- foo") # => "foo"
#
#   # Emit some YAML
#   Psych.dump("foo")     # => "--- foo\n...\n"
#   { :a => 'b'}.to_yaml  # => "---\n:a: b\n"
#
# Got more time on your hands?  Keep on reading!
#
# == YAML Parsing
#
# Psych provides a range of interfaces for parsing a YAML document ranging from
# low level to high level, depending on your parsing needs.  At the lowest
# level, is an event based parser.  Mid level is access to the raw YAML AST,
# and at the highest level is the ability to unmarshal YAML to Ruby objects.
#
# == YAML Emitting
#
# Psych provides a range of interfaces ranging from low to high level for
# producing YAML documents.  Very similar to the YAML parsing interfaces, Psych
# provides at the lowest level, an event based system, mid-level is building
# a YAML AST, and the highest level is converting a Ruby object straight to
# a YAML document.
#
# == High-level API
#
# === Parsing
#
# The high level YAML parser provided by Psych simply takes YAML as input and
# returns a Ruby data structure.  For information on using the high level parser
# see Psych.load
#
# ==== Reading from a string
#
#   Psych.load("--- a")             # => 'a'
#   Psych.load("---\n - a\n - b")   # => ['a', 'b']
#
# ==== Reading from a file
#
#   Psych.load_file("database.yml")
#
# ==== Exception handling
#
#   begin
#     # The second argument changes only the exception contents
#     Psych.parse("--- `", "file.txt")
#   rescue Psych::SyntaxError => ex
#     ex.file    # => 'file.txt'
#     ex.message # => "(file.txt): found character that cannot start any token"
#   end
#
# === Emitting
#
# The high level emitter has the easiest interface.  Psych simply takes a Ruby
# data structure and converts it to a YAML document.  See Psych.dump for more
# information on dumping a Ruby data structure.
#
# ==== Writing to a string
#
#   # Dump an array, get back a YAML string
#   Psych.dump(['a', 'b'])  # => "---\n- a\n- b\n"
#
#   # Dump an array to an IO object
#   Psych.dump(['a', 'b'], StringIO.new)  # => #<StringIO:0x000001009d0890>
#
#   # Dump an array with indentation set
#   Psych.dump(['a', ['b']], :indentation => 3) # => "---\n- a\n-  - b\n"
#
#   # Dump an array to an IO with indentation set
#   Psych.dump(['a', ['b']], StringIO.new, :indentation => 3)
#
# ==== Writing to a file
#
# Currently there is no direct API for dumping Ruby structure to file:
#
#   File.open('database.yml', 'w') do |file|
#     file.write(Psych.dump(['a', 'b']))
#   end
#
# == Mid-level API
#
# === Parsing
#
# Psych provides access to an AST produced from parsing a YAML document.  This
# tree is built using the Psych::Parser and Psych::TreeBuilder.  The AST can
# be examined and manipulated freely.  Please see Psych::parse_stream,
# Psych::Nodes, and Psych::Nodes::Node for more information on dealing with
# YAML syntax trees.
#
# ==== Reading from a string
#
#   # Returns Psych::Nodes::Stream
#   Psych.parse_stream("---\n - a\n - b")
#
#   # Returns Psych::Nodes::Document
#   Psych.parse("---\n - a\n - b")
#
# ==== Reading from a file
#
#   # Returns Psych::Nodes::Stream
#   Psych.parse_stream(File.read('database.yml'))
#
#   # Returns Psych::Nodes::Document
#   Psych.parse_file('database.yml')
#
# ==== Exception handling
#
#   begin
#     # The second argument changes only the exception contents
#     Psych.parse("--- `", "file.txt")
#   rescue Psych::SyntaxError => ex
#     ex.file    # => 'file.txt'
#     ex.message # => "(file.txt): found character that cannot start any token"
#   end
#
# === Emitting
#
# At the mid level is building an AST.  This AST is exactly the same as the AST
# used when parsing a YAML document.  Users can build an AST by hand and the
# AST knows how to emit itself as a YAML document.  See Psych::Nodes,
# Psych::Nodes::Node, and Psych::TreeBuilder for more information on building
# a YAML AST.
#
# ==== Writing to a string
#
#   # We need Psych::Nodes::Stream (not Psych::Nodes::Document)
#   stream = Psych.parse_stream("---\n - a\n - b")
#
#   stream.to_yaml # => "---\n- a\n- b\n"
#
# ==== Writing to a file
#
#   # We need Psych::Nodes::Stream (not Psych::Nodes::Document)
#   stream = Psych.parse_stream(File.read('database.yml'))
#
#   File.open('database.yml', 'w') do |file|
#     file.write(stream.to_yaml)
#   end
#
# == Low-level API
#
# === Parsing
#
# The lowest level parser should be used when the YAML input is already known,
# and the developer does not want to pay the price of building an AST or
# automatic detection and conversion to Ruby objects.  See Psych::Parser for
# more information on using the event based parser.
#
# ==== Reading to Psych::Nodes::Stream structure
#
#   parser = Psych::Parser.new(TreeBuilder.new) # => #<Psych::Parser>
#   parser = Psych.parser                       # it's an alias for the above
#
#   parser.parse("---\n - a\n - b")             # => #<Psych::Parser>
#   parser.handler                              # => #<Psych::TreeBuilder>
#   parser.handler.root                         # => #<Psych::Nodes::Stream>
#
# ==== Receiving an events stream
#
#   parser = Psych::Parser.new(Psych::Handlers::Recorder.new)
#
#   parser.parse("---\n - a\n - b")
#   parser.events # => [list of [event, args] lists]
#                 # event is one of: Psych::Handler::EVENTS
#                 # args are the arguments passed to the event
#
# === Emitting
#
# The lowest level emitter is an event based system.  Events are sent to a
# Psych::Emitter object.  That object knows how to convert the events to a YAML
# document.  This interface should be used when document format is known in
# advance or speed is a concern.  See Psych::Emitter for more information.
#
# ==== Writing to a Ruby structure
#
#   Psych.parser.parse("--- a")       # => #<Psych::Parser>
#
#   parser.handler.first              # => #<Psych::Nodes::Stream>
#   parser.handler.first.to_ruby      # => ["a"]
#
#   parser.handler.root.first         # => #<Psych::Nodes::Document>
#   parser.handler.root.first.to_ruby # => "a"
#
#   # You can instantiate an Emitter manually
#   Psych::Visitors::ToRuby.new.accept(parser.handler.root.first)
#   # => "a"

module Psych
  # The version is Psych you're using
  VERSION         = '2.0.3'

  # The version of libyaml Psych is using
  LIBYAML_VERSION = Psych.libyaml_version.join '.'

  ###
  # Load +yaml+ in to a Ruby data structure.  If multiple documents are
  # provided, the object contained in the first document will be returned.
  # +filename+ will be used in the exception message if any exception is raised
  # while parsing.
  #
  # Raises a Psych::SyntaxError when a YAML syntax error is detected.
  #
  # Example:
  #
  #   Psych.load("--- a")             # => 'a'
  #   Psych.load("---\n - a\n - b")   # => ['a', 'b']
  #
  #   begin
  #     Psych.load("--- `", "file.txt")
  #   rescue Psych::SyntaxError => ex
  #     ex.file    # => 'file.txt'
  #     ex.message # => "(file.txt): found character that cannot start any token"
  #   end
  def self.load yaml, filename = nil
    result = parse(yaml, filename)
    result ? result.to_ruby : result
  end

  ###
  # Safely load the yaml string in +yaml+.  By default, only the following
  # classes are allowed to be deserialized:
  #
  # * TrueClass
  # * FalseClass
  # * NilClass
  # * Numeric
  # * String
  # * Array
  # * Hash
  #
  # Recursive data structures are not allowed by default.  Arbitrary classes
  # can be allowed by adding those classes to the +whitelist+.  They are
  # additive.  For example, to allow Date deserialization:
  #
  #   Psych.safe_load(yaml, [Date])
  #
  # Now the Date class can be loaded in addition to the classes listed above.
  #
  # Aliases can be explicitly allowed by changing the +aliases+ parameter.
  # For example:
  #
  #   x = []
  #   x << x
  #   yaml = Psych.dump x
  #   Psych.safe_load yaml               # => raises an exception
  #   Psych.safe_load yaml, [], [], true # => loads the aliases
  #
  # A Psych::DisallowedClass exception will be raised if the yaml contains a
  # class that isn't in the whitelist.
  #
  # A Psych::BadAlias exception will be raised if the yaml contains aliases
  # but the +aliases+ parameter is set to false.
  def self.safe_load yaml, whitelist_classes = [], whitelist_symbols = [], aliases = false, filename = nil
    result = parse(yaml, filename)
    return unless result

    class_loader = ClassLoader::Restricted.new(whitelist_classes.map(&:to_s),
                                               whitelist_symbols.map(&:to_s))
    scanner      = ScalarScanner.new class_loader
    if aliases
      visitor = Visitors::ToRuby.new scanner, class_loader
    else
      visitor = Visitors::NoAliasRuby.new scanner, class_loader
    end
    visitor.accept result
  end

  ###
  # Parse a YAML string in +yaml+.  Returns the Psych::Nodes::Document.
  # +filename+ is used in the exception message if a Psych::SyntaxError is
  # raised.
  #
  # Raises a Psych::SyntaxError when a YAML syntax error is detected.
  #
  # Example:
  #
  #   Psych.parse("---\n - a\n - b") # => #<Psych::Nodes::Document:0x00>
  #
  #   begin
  #     Psych.parse("--- `", "file.txt")
  #   rescue Psych::SyntaxError => ex
  #     ex.file    # => 'file.txt'
  #     ex.message # => "(file.txt): found character that cannot start any token"
  #   end
  #
  # See Psych::Nodes for more information about YAML AST.
  def self.parse yaml, filename = nil
    parse_stream(yaml, filename) do |node|
      return node
    end
    false
  end

  ###
  # Parse a file at +filename+. Returns the Psych::Nodes::Document.
  #
  # Raises a Psych::SyntaxError when a YAML syntax error is detected.
  def self.parse_file filename
    File.open filename, 'r:bom|utf-8' do |f|
      parse f, filename
    end
  end

  ###
  # Returns a default parser
  def self.parser
    Psych::Parser.new(TreeBuilder.new)
  end

  ###
  # Parse a YAML string in +yaml+.  Returns the Psych::Nodes::Stream.
  # This method can handle multiple YAML documents contained in +yaml+.
  # +filename+ is used in the exception message if a Psych::SyntaxError is
  # raised.
  #
  # If a block is given, a Psych::Nodes::Document node will be yielded to the
  # block as it's being parsed.
  #
  # Raises a Psych::SyntaxError when a YAML syntax error is detected.
  #
  # Example:
  #
  #   Psych.parse_stream("---\n - a\n - b") # => #<Psych::Nodes::Stream:0x00>
  #
  #   Psych.parse_stream("--- a\n--- b") do |node|
  #     node # => #<Psych::Nodes::Document:0x00>
  #   end
  #
  #   begin
  #     Psych.parse_stream("--- `", "file.txt")
  #   rescue Psych::SyntaxError => ex
  #     ex.file    # => 'file.txt'
  #     ex.message # => "(file.txt): found character that cannot start any token"
  #   end
  #
  # See Psych::Nodes for more information about YAML AST.
  def self.parse_stream yaml, filename = nil, &block
    if block_given?
      parser = Psych::Parser.new(Handlers::DocumentStream.new(&block))
      parser.parse yaml, filename
    else
      parser = self.parser
      parser.parse yaml, filename
      parser.handler.root
    end
  end

  ###
  # call-seq:
  #   Psych.dump(o)               -> string of yaml
  #   Psych.dump(o, options)      -> string of yaml
  #   Psych.dump(o, io)           -> io object passed in
  #   Psych.dump(o, io, options)  -> io object passed in
  #
  # Dump Ruby object +o+ to a YAML string.  Optional +options+ may be passed in
  # to control the output format.  If an IO object is passed in, the YAML will
  # be dumped to that IO object.
  #
  # Example:
  #
  #   # Dump an array, get back a YAML string
  #   Psych.dump(['a', 'b'])  # => "---\n- a\n- b\n"
  #
  #   # Dump an array to an IO object
  #   Psych.dump(['a', 'b'], StringIO.new)  # => #<StringIO:0x000001009d0890>
  #
  #   # Dump an array with indentation set
  #   Psych.dump(['a', ['b']], :indentation => 3) # => "---\n- a\n-  - b\n"
  #
  #   # Dump an array to an IO with indentation set
  #   Psych.dump(['a', ['b']], StringIO.new, :indentation => 3)
  def self.dump o, io = nil, options = {}
    if Hash === io
      options = io
      io      = nil
    end

    visitor = Psych::Visitors::YAMLTree.create options
    visitor << o
    visitor.tree.yaml io, options
  end

  ###
  # Dump a list of objects as separate documents to a document stream.
  #
  # Example:
  #
  #   Psych.dump_stream("foo\n  ", {}) # => "--- ! \"foo\\n  \"\n--- {}\n"
  def self.dump_stream *objects
    visitor = Psych::Visitors::YAMLTree.create({})
    objects.each do |o|
      visitor << o
    end
    visitor.tree.yaml
  end

  ###
  # Dump Ruby +object+ to a JSON string.
  def self.to_json object
    visitor = Psych::Visitors::JSONTree.create
    visitor << object
    visitor.tree.yaml
  end

  ###
  # Load multiple documents given in +yaml+.  Returns the parsed documents
  # as a list.  If a block is given, each document will be converted to Ruby
  # and passed to the block during parsing
  #
  # Example:
  #
  #   Psych.load_stream("--- foo\n...\n--- bar\n...") # => ['foo', 'bar']
  #
  #   list = []
  #   Psych.load_stream("--- foo\n...\n--- bar\n...") do |ruby|
  #     list << ruby
  #   end
  #   list # => ['foo', 'bar']
  #
  def self.load_stream yaml, filename = nil
    if block_given?
      parse_stream(yaml, filename) do |node|
        yield node.to_ruby
      end
    else
      parse_stream(yaml, filename).children.map { |child| child.to_ruby }
    end
  end

  ###
  # Load the document contained in +filename+.  Returns the yaml contained in
  # +filename+ as a Ruby object
  def self.load_file filename
    File.open(filename, 'r:bom|utf-8') { |f| self.load f, filename }
  end

  # :stopdoc:
  @domain_types = {}
  def self.add_domain_type domain, type_tag, &block
    key = ['tag', domain, type_tag].join ':'
    @domain_types[key] = [key, block]
    @domain_types["tag:#{type_tag}"] = [key, block]
  end

  def self.add_builtin_type type_tag, &block
    domain = 'yaml.org,2002'
    key = ['tag', domain, type_tag].join ':'
    @domain_types[key] = [key, block]
  end

  def self.remove_type type_tag
    @domain_types.delete type_tag
  end

  @load_tags = {}
  @dump_tags = {}
  def self.add_tag tag, klass
    @load_tags[tag] = klass.name
    @dump_tags[klass] = tag
  end

  class << self
    attr_accessor :load_tags
    attr_accessor :dump_tags
    attr_accessor :domain_types
  end
  # :startdoc:
end