compare_parsey_prism_depth.rb

require 'prism'
require 'ripper'

def parsey_extract_locations(code)
  lines = code.lines
  line_indexes = lines.reduce([0]) { _1 << _1.last + _2.bytesize }
  code_index = ->(line, col) { line_indexes[line - 1] + col }
  locations = []
  each_node = -> node do
    locs = node.locations.compact
    unless locs.empty?
      from = locs.flat_map { code_index.call(it.first_lineno, it.first_column) }.min
      to = locs.flat_map { code_index.call(it.last_lineno, it.last_column) }.max
      locations << [from, to]
    end
    node.children.each do |child|
      each_node.call(child) if child.is_a?(RubyVM::AbstractSyntaxTree::Node)
    end
  end
  each_node.call(RubyVM::AbstractSyntaxTree.parse(code))
  locations
end

def prism_extract_locations(code)
  locations = []
  each_node = ->node do
    locations << [node.location.start_offset, node.location.end_offset]
    node.compact_child_nodes.each(&each_node)
  end
  each_node.call(Prism.parse(code).value)
  locations
end

def print_depth(code, locations)
  depth = 0
  last_pos = 0
  segments = []
  locations.uniq.flat_map { [[_1, +1], [_2, -1]] }.sort.each do |pos, open_close|
    segments << [code.byteslice(last_pos...pos), depth] unless last_pos == pos
    depth += open_close
    last_pos = pos
  end
  puts(
    segments.map do |segment, depth|
      c = [255 - 3 * depth, 232].max
      "\e[48;5;#{c}m#{segment}\e[0m"
    end.join
  )
end

def compare(code)
  print_depth(code, parsey_extract_locations(code))
  print_depth(code, prism_extract_locations(code))
end

compare('def f = not a in b rescue c')