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parser translation

Prism ships with the ability to translate its syntax tree into the syntax tree used by the whitequark/parser gem. This allows you to use tools built on top of the parser gem with the prism parser.

Usage

The parser gem provides multiple parsers to support different versions of the Ruby grammar. This includes all of the Ruby versions going back to 1.8, as well as third-party parsers like MacRuby and RubyMotion. The prism gem provides another parser that uses the prism parser to build the syntax tree.

You can use the prism parser like you would any other. After requiring the parser, you should be able to call any of the regular Parser::Base APIs that you would normally use.

require "prism"

Prism::Translation::Parser.parse_file("path/to/file.rb")

RuboCop

Prism as a parser engine is directly supported since RuboCop 1.62. The class used for parsing is Prism::Translation::Parser.

First, specify prism in your Gemfile:

gem "prism"

To use Prism with RuboCop, specify ParserEngine and TargetRubyVersion in your RuboCop configuration file:

AllCops:
  ParserEngine: parser_prism
  TargetRubyVersion: 3.3

The default value for ParserEngine is parser_whitequark, which indicates the Parser gem. You need to explicitly switch it to parser_prism to indicate Prism. Additionally, the value for TargetRubyVersion must be specified as 3.3 or higher, as Prism supports parsing versions of Ruby 3.3 and higher. The parser class is determined by the combination of values for ParserEngine and TargetRubyVersion. For example, if TargetRubyVersion: 3.3, parsing is performed by Prism::Translation::Parser33, and for TargetRubyVersion 3.4, parsing is performed by Prism::Translation::Parser34.

For further information, please refer to the RuboCop documentation: https://docs.rubocop.org/rubocop/configuration.html#setting-the-parser-engine