Find Ruby syntax patterns with Prism.

Write your pattern in Ruby.

require 'syntax_finder'

# Count up all `if` statements (if/elsif/?:) and `then` keywords.

class IfThenFinder < SyntaxFinder
  def look node
    if node.type == :if_node
      if node.if_keyword_loc # if or elsif
        inc node.if_keyword_loc.slice
        if node.then_keyword_loc
          inc 'then'
          # inc path: @file
        end
      else
        # a ? b : c
        inc '?:'
      end
    end
  end
end

and run the script with Ruby script file names listed in STDIN like this.

$ find ruby/ruby -name '*.rb' | ruby samples/if_then_finder.rb
[[[:FILES, 7_705], [:FAILED_PARSE, 3]],
 [["if", 14_886], ["?:", 1_806], ["elsif", 922], ["then", 184]]]

In this case, with *.rb files in ruby/ruby directory, there are

• There are 7_705 files
  • but 3 files are failed to prase
• In the files, there are
  • 14_886 if statements
  • 1_806 ?: style if statements
  • 922 elsif statements
  • 184 then statements

You can specify files with arguments like that:

$ ruby samples/if_then_finder.rb samples/*.rb
 ruby -I ./lib/ samples/then_finder.rb samples/*
[[[:FILES, 18]], [["if", 31], ["elsif", 2], ["then", 1]]]

You can specify -j or -jN for parallel processing like that:

$ time find ruby/ruby -name '*.rb' | ruby -I ./lib/ samples/if_then_finder.rb
[[[:FILES, 7_705], [:FAILED_PARSE, 3]],
 [["if", 14_886], ["?:", 1_806], ["elsif", 922], ["then", 184]]]

real    0m3.952s
user    0m2.566s
sys     0m0.088s

$ time find ruby/ruby -name '*.rb' | ruby -I ./lib/ samples/if_then_finder.rb -j
[[[:FILES, 7_705], [:FAILED_PARSE, 3]],
 [["if", 14_886], ["?:", 1_806], ["elsif", 922], ["then", 184]]]

real    0m1.281s
user    0m5.822s
sys     0m1.141s

1. Define a class derived with SyntaxFinder class.
2. Define a look(node) method with your expected pattern. node is Prism's node.
3. Use inc(key) if you want to aggregate the statistics in look().

See examples/ for more examples.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test-unit to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/ko1/syntax_finder.

The gem is available as open source under the terms of the MIT License.