Synvert core provides a set of DSLs to rewrite (find and replace) ruby code. e.g.

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

  description <<~EOS
    It converts `map` and `flatten` to `flat_map`

    ```ruby
    enum.map do
      # do something
    end.flatten
    ```

    =>

    ```ruby
    enum.flat_map do
      # do something
    end
    ```
  EOS

  within_files Synvert::ALL_RUBY_FILES + Synvert::ALL_RAKE_FILES do
    find_node '.send [receiver=.block [caller=.send[message=map]]] [message=flatten] [arguments.size=0]' do
      group do
        delete :message, :dot
        replace 'receiver.caller.message', with: 'flat_map'
      end
    end
  end
end

It also supports to add callbacks to visit ast nodes.

Synvert::Helper.new 'ruby/parse' do |options|
  configure(parser: Synvert::PRISM_PARSER)

  with_configurations(number_of_workers: 1) do
    class_names = []
    within_file Synvert::ALL_RUBY_FILES do
      add_callback :class_node, at: 'start' do |node|
        class_names << node.name.to_source
      end
    end
    # class_names is an array of class names
  end
end

Want to see more examples, check out synvert-snippets-ruby.

Want to use the CLI, check out synvert-ruby.

DSLs are as follows

• configure - configure the rewriter
• description - describe what the rewriter does
• if_ruby - check if ruby version is greater than or equal to the specified ruby version
• if_gem - compare version of specified gem
• within_files - find specified files
• within_file - alias to within_files
• add_file - add a new file
• remove_file - remove a file
• helper_method - define a helper method
• add_snippet - call another rewriter
• call_helper - call a shared rewriter
• with_configurations - execute a block of code with temporary configurations

Scopes:

• within_node - recursively find matching ast nodes
• with_node - alias to within_node
• find_node - alias to within_node
• goto_node - go to a child node

Conditions:

• if_exist_node - check if matching node exist in the child nodes
• unless_exist_node - check if matching node doesn't exist in the child nodes

Actions:

• append - append the code to the bottom of current node body
• prepend - prepend the code to the bottom of current node body
• insert - insert code
• insert_after - insert the code next to the current node
• insert_before - insert the code previous to the current node
• replace - replace the code of specified child nodes
• delete - delete the code in specified child nodes
• remove - remove the whole code of current node
• wrap - wrap the current node with prefix and suffix code
• replace_with - replace the whole code of current node
• warn - warn message
• replace_erb_stmt_with_expr - replace erb stmt code to expr code
• noop - no operation
• group - group actions
• add_action - add custom action

Callbacks:

• add_callback - add callback when visiting ast nodes

Others:

• wrap_with_quotes - wrap string code with single or double quotes
• add_leading_spaces - add leading spaces before the string code

Attributes:

• file_path - current file path
• node - current ast node
• mutation_adapter - mutation adapter to get some helper methods