Parslet Woes

failing_example.rb

require 'parslet'
require 'pp'

def parse(input)
  parser = SongParser.new
  begin
    tree = parser.parse(input)
  rescue Parslet::ParseFailed => error
    puts error, parser.root.error_tree
  end
  tree
end

class SongParser < Parslet::Parser
  # Convenience: lyrics can have ignored characters after the
  # last timecode on a line
  rule(:junk) { (line_end.absent? >> any).repeat }

  # Convenience: End of Line / Whitespace matchers
  rule(:line_end) { match('[\r\n]').repeat(1) }
  rule(:spaces) { match('\s').repeat(1) }
  rule(:spaces?) { spaces.maybe }

  # Elements
  rule(:syllable) { (timecode.absent? >> any).repeat(1) }
  rule(:timecode) {
    str('[') >> match('\d').repeat(1).as(:min) >>
    str(':') >> match('\d').repeat(1).as(:sec) >>
    str(':') >> match('\d').repeat(1).as(:msec) >> str(']')
  }

  # Groups
  rule(:pair) { timecode >> syllable.as(:syllable) }
  rule(:line) { (pair.repeat >> timecode).as(:line) >> junk.maybe >> line_end }
  rule(:song) { line.repeat.as(:lines) }

  root :song
end

input  = "[01:06:07]Beat[01:06:30]ing [01:06:56]up [01:06:83]the [01:07:09]wrong "
input << "[01:07:52]guy[01:08:03]\n[01:08:50]Oh [01:08:93]man![01:09:48]\n"
input_no_trailing_new_line = input.chomp

pp parse(input)
# Produces:
#
# Don't know what to do with [01:06:07]Beat[01:06:30]ing [01:06:56]up [01:06:83]the [01:07:09]wrong [01:07:52]guy[01:08:03]
# [01:0 at line 1 char 1.
# `- Failed to match sequence (line:(PAIR{0, } TIMECODE) JUNK? LINE_END) at line 1 char 1.
#    `- Failed to match sequence (PAIR{0, } TIMECODE) at line 3 char 1.
#       `- Failed to match sequence ('[' min:(\\d{1, }) ':' sec:(\\d{1, }) ':' msec:(\\d{1, }) ']') at line 3 char 1.
#          `- Premature end of input at line 3 char 1.


pp parse(input_no_trailing_new_line)
# Produces:
#
# Don't know what to do with [01:06:07]Beat[01:06:30]ing [01:06:56]up [01:06:83]the [01:07:09]wrong [01:07:52]guy[01:08:03]
# [01:0 at line 1 char 1.
# `- Failed to match sequence (line:(PAIR{0, } TIMECODE) JUNK? LINE_END) at line 2 char 38.
#    `- Expected at least 1 of [\\r\\n] at line 2 char 38.
#       `- Failed to match [\\r\\n] at line 2 char 38.

simpler_working_example.rb

require 'parslet'
require 'pp'

def parse(input)
  parser = SongParser.new
  begin
    tree = parser.parse(input)
  rescue Parslet::ParseFailed => error
    puts error, parser.root.error_tree
  end
  tree
end

class SongParser < Parslet::Parser
  rule(:line_end) { match('[\r\n]').repeat(1) }
  rule(:junk) { (line_end.absent? >> any).repeat }

  rule(:line) { junk.as(:line) >> line_end }
  rule(:song) { line.repeat.as(:lines) }

  root :song
end

input  = "[01:06:07]Beat[01:06:30]ing [01:06:56]up [01:06:83]the [01:07:09]wrong "
input << "[01:07:52]guy[01:08:03]\n[01:08:50]Oh [01:08:93]man![01:09:48]\n"
input_no_trailing_new_line = input.chomp

pp parse(input) # Works fine
pp parse(input_no_trailing_new_line) # Explodes