RubyVM::AbstractSyntaxTree

4 class methods

AbstractSyntaxTree provides methods to parse Ruby code into abstract syntax trees. The nodes in the tree are instances of RubyVM::AbstractSyntaxTree::Node.

This module is MRI specific as it exposes implementation details of the MRI abstract syntax tree.

This module is experimental and its API is not stable, therefore it might change without notice. As examples, the order of children nodes is not guaranteed, the number of children nodes might change, there is no way to access children nodes by name, etc.

If you are looking for a stable API or an API working under multiple Ruby implementations, consider using the parser gem or Ripper. If you would like to make RubyVM::AbstractSyntaxTree stable, please join the discussion at bugs.ruby-lang.org/issues/14844.

Class methods 4

.node_id_for_backtrace_location .of .parse .parse_file

Ruby version changes 2

3.2

Add error_tolerant option for parse, parse_file and of. [Feature #19013] With this option

SyntaxError is suppressed
AST is returned for invalid input
end is complemented when a parser reaches to the end of input but end is insufficient
end is treated as keyword based on indent

Example

# Without error_tolerant option
root = RubyVM::AbstractSyntaxTree.parse(<<~RUBY)
def m
  a = 10
  if
end
RUBY
# => <internal:ast>:33:in `parse': syntax error, unexpected `end' (SyntaxError)

# With error_tolerant option
root = RubyVM::AbstractSyntaxTree.parse(<<~RUBY, error_tolerant: true)
def m
  a = 10
  if
end
RUBY
p root # => #<RubyVM::AbstractSyntaxTree::Node:SCOPE@1:0-4:3>

# `end` is treated as keyword based on indent
root = RubyVM::AbstractSyntaxTree.parse(<<~RUBY, error_tolerant: true)
module Z
  class Foo
    foo.
  end

  def bar
  end
end
RUBY
p root.children[-1].children[-1].children[-1].children[-2..-1]
# => [#<RubyVM::AbstractSyntaxTree::Node:CLASS@2:2-4:5>, #<RubyVM::AbstractSyntaxTree::Node:DEFN@6:2-7:5>]

Add keep_tokens option for parse, parse_file and of. Add tokens and all_tokens for RubyVM::AbstractSyntaxTree::Node [Feature #19070]

Example

root = RubyVM::AbstractSyntaxTree.parse("x = 1 + 2", keep_tokens: true)
root.tokens # => [[0, :tIDENTIFIER, "x", [1, 0, 1, 1]], [1, :tSP, " ", [1, 1, 1, 2]], ...]
root.tokens.map{_1[2]}.join # => "x = 1 + 2"