Back to Blog

Ruby 2.6 adds RubyVM::AST module

on October 2, 2018
This blog is part of our Ruby 2.6 series.

Ruby 2.6.0 was released on Dec 25, 2018.

Ruby 2.6 added RubyVM::AST to generate the Abstract Syntax Tree of code. Please note, this feature is experimental and under active development.

As of now, RubyVM::AST supports two methods: parse and parse_file.

parse method takes a string as a parameter and returns the root node of the tree in the form of the object, RubyVM::AST::Node.

parse_file method takes the file name as a parameter and returns the root node of the tree in the form of the object, RubyVM::AST::Node.

Ruby 2.6.0-preview2

1irb> RubyVM::AST.parse("(1..100).select { |num| num % 5 == 0 }")
2=> #<RubyVM::AST::Node(NODE_SCOPE(0) 1:0, 1:38): >
3
4irb> RubyVM::AST.parse_file("/Users/amit/app.rb")
5=> #<RubyVM::AST::Node(NODE_SCOPE(0) 1:0, 1:38): >

RubyVM::AST::Node has seven public instance methods - children, first_column, first_lineno, inspect, last_column, last_lineno and type.

Ruby 2.6.0-preview2

1irb> ast_node = RubyVM::AST.parse("(1..100).select { |num| num % 5 == 0 }")
2=> #<RubyVM::AST::Node(NODE_SCOPE(0) 1:0, 1:38): >
3
4irb> ast_node.children
5=> [nil, #<RubyVM::AST::Node(NODE_ITER(9) 1:0, 1:38): >]
6
7irb> ast_node.first_column
8=> 0
9
10irb> ast_node.first_lineno
11=> 1
12
13irb> ast_node.inspect
14=> "#<RubyVM::AST::Node(NODE_SCOPE(0) 1:0, 1:38): >"
15
16irb> ast_node.last_column
17=> 38
18
19irb> ast_node.last_lineno
20=> 1
21
22irb> ast_node.type
23=> "NODE_SCOPE"

This module will majorly help in building a static code analyzer and formatter.


You might also like

If you liked this blog post, check out similar ones from BigBinary