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module · Ruby 4.1

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.

Prism is the official Ruby API to parse Ruby code. It has a stable API and is available on most Ruby implementations. Therefore, it is the recommended replacement. Using RubyVM::AbstractSyntaxTree is discouraged for new code for the reasons above and because AbstractSyntaxTree might become deprecated in the future.

Class methods 4

.node_id_for_backtrace_location .of .parse .parse_file

Ruby version changes 4

3.4
- Add RubyVM::AbstractSyntaxTree::Node#locations method which returns location objects associated with the AST node. [Feature #20624]
- Add RubyVM::AbstractSyntaxTree::Location class which holds location information. [Feature #20624]

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"