Synvert now supports the Prism parser

Ruby 3.3 introduced a new standard library, Prism, a parser for the Ruby language. Prism is designed for portability, error tolerance, and maintainability.

I have integrated the Prism parser into Synvert using the Adapter pattern in the node-query and node-mutation gems. This involved implementing a Prism parser adapter, which was straightforward due to the flexible design of these gems.

The Prism adapter for node-query is available here: https://github.com/synvert-hq/node-query-ruby/blob/main/lib/node_query/adapter/prism.rb. It implements methods is_node?, get_node_type, get_source, get_children, get_siblings.

The Prism adapter for node-mutation can be found here: https://github.com/synvert-hq/node-mutation-ruby/blob/main/lib/node_mutation/adapter/prism.rb. This adapter includes methods get_source, rewritten_source, file_source, child_node_range, get_start, get_end, get_start_loc, get_end_loc.

In synvert-core, I simply added a PRISM_PARSER constant for parser configuration. When a snippet uses the PRISM_PARSER, it utilizes Prism to parse the source code and pass the AST nodes to node-query and node-mutation.

Synvert::Rewriter.new 'group', 'name' do
  configure(parser: Synvert::PRISM_PARSER)
end

For example, the ruby/map_and_flatten_to_flat_map snippet is using the PARSER_PARSER, let’s rewrite it to use the PRISM_PARSER. If you are unfamiliar with Prism AST nodes, you can use the Synvert Playground to generate snippets with the Prism parser.

# frozen_string_literal: true

Synvert::Rewriter.new 'ruby', 'map_and_flatten_to_flat_map' do
  configure(parser: Synvert::PRISM_PARSER)

  within_files Synvert::ALL_RUBY_FILES + Synvert::ALL_RAKE_FILES do
    # enum.map do |item|
    #   # do something
    # end.flatten
    # =>
    # enum.flat_map do |item|
    #   # do something
    # end
    find_node '.call_node[receiver=.call_node[name=map][arguments=nil][block=.block_node]][name=flatten][arguments=nil]' do
      group do
        delete :call_operator, :name
        replace 'receiver.name', with: 'flat_map'
      end
    end
  end
end

Run the test command bundle exec rspec spec/ruby/map_and_flatten_to_flat_map_spec.rb to ensure the snippet functions as expected.