Helper tool to debug parser and formatter
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.gitignore Initial commit Oct 9, 2018
LICENSE Initial commit Oct 9, 2018 Update readme Oct 10, 2018
shard.lock Initial commit Oct 9, 2018
shard.yml Initial commit Oct 9, 2018



$ git checkout
$ cd crystal-ast-helper
$ shards
$ crystal src/

$ open http://localhost:9090

If you want to use with crystal head use:

$ path/to/crystal-clone/bin/crystal src/


When opening http://localhost:9090 you will be able to:

  • input source
  • view the output according to the formatter
  • view the tokens returned by the lexer used for parsing and for formatting
    • view the tokens consumed so far even if the formatter fails
  • view the stack trace of each token
  • view the AST of the whole program


  1. Fork it (
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request


  • bcardiff Brian J. Cardiff - creator, maintainer