# frozen_string_literal: true require_relative 'nodes/node' require_relative 'nodes/stream' require_relative 'nodes/document' require_relative 'nodes/sequence' require_relative 'nodes/scalar' require_relative 'nodes/mapping' require_relative 'nodes/alias' module Psych ### # = Overview # # When using Psych.load to deserialize a YAML document, the document is # translated to an intermediary AST. That intermediary AST is then # translated in to a Ruby object graph. # # In the opposite direction, when using Psych.dump, the Ruby object graph is # translated to an intermediary AST which is then converted to a YAML # document. # # Psych::Nodes contains all of the classes that make up the nodes of a YAML # AST. You can manually build an AST and use one of the visitors (see # Psych::Visitors) to convert that AST to either a YAML document or to a # Ruby object graph. # # Here is an example of building an AST that represents a list with one # scalar: # # # Create our nodes # stream = Psych::Nodes::Stream.new # doc = Psych::Nodes::Document.new # seq = Psych::Nodes::Sequence.new # scalar = Psych::Nodes::Scalar.new('foo') # # # Build up our tree # stream.children << doc # doc.children << seq # seq.children << scalar # # The stream is the root of the tree. We can then convert the tree to YAML: # # stream.to_yaml => "---\n- foo\n" # # Or convert it to Ruby: # # stream.to_ruby => [["foo"]] # # == YAML AST Requirements # # A valid YAML AST *must* have one Psych::Nodes::Stream at the root. A # Psych::Nodes::Stream node must have 1 or more Psych::Nodes::Document nodes # as children. # # Psych::Nodes::Document nodes must have one and *only* one child. That child # may be one of: # # * Psych::Nodes::Sequence # * Psych::Nodes::Mapping # * Psych::Nodes::Scalar # # Psych::Nodes::Sequence and Psych::Nodes::Mapping nodes may have many # children, but Psych::Nodes::Mapping nodes should have an even number of # children. # # All of these are valid children for Psych::Nodes::Sequence and # Psych::Nodes::Mapping nodes: # # * Psych::Nodes::Sequence # * Psych::Nodes::Mapping # * Psych::Nodes::Scalar # * Psych::Nodes::Alias # # Psych::Nodes::Scalar and Psych::Nodes::Alias are both terminal nodes and # should not have any children. module Nodes end end