Class: Pegparse::ParserErrors

Inherits:
Object
  • Object
show all
Defined in:
lib/pegparse/parser_errors.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ ParserErrors 



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# File 'lib/pegparse/parser_errors.rb', line 17

def initialize
  @farthest_pos = 0
  @farthest_errors = []
end

Instance Method Details

#best_errors ⇒ Array<Pegparse::ParseError>

get meaningful errors



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# File 'lib/pegparse/parser_errors.rb', line 58

def best_errors
  optional_memos = @farthest_errors.map.with_index do |stack, index|
    Pegparse::ParseErrorLocation.new(
      index_in_errors: index,
      start_positions_of_optional: stack.select{|rule| rule.reason == :optional}.map{|rule| rule.pos}
    )
  end

  best_memos = []
  optional_memos.each do |memo|
    if best_memos.empty?
      best_memos << memo
      next
    end
    cmp = compare_optional_memo(memo, best_memos[0])
    if cmp < 0
      best_memos = [memo]
      next
    elsif cmp == 0
      best_memos << memo
      next
    else
      next
    end
  end

  bests = best_memos.map{|x| @farthest_errors[x.index_in_errors]}
  
  result = bests.map do |stack|
    stack.select{|x| x.reason != :optional}.last(2)
  end
  result
end

#clear_errors ⇒ Object

remove all stored errors



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# File 'lib/pegparse/parser_errors.rb', line 93

def clear_errors
  @farthest_pos = 0
  @farthest_errors = []
end

#compare_optional_memo(a, b) ⇒ Object

compare two errors which is better by parsing descent path

(optional matching starts more earlier, priority becomes lower)



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# File 'lib/pegparse/parser_errors.rb', line 41

def compare_optional_memo(a, b)
  a_opts = a.start_positions_of_optional
  b_opts = b.start_positions_of_optional

  for i in 0...[a_opts.size, b_opts.size].min
    if a_opts[i] > b_opts[i]
      return -1
    end
    if a_opts[i] < b_opts[i]
      return 1
    end
  end
  return a_opts.size <=> b_opts.size
end

#save_error(pos, rule_stack, reason) ⇒ Object

just save parsing error



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# File 'lib/pegparse/parser_errors.rb', line 26

def save_error(pos, rule_stack, reason)
  return if pos < @farthest_pos
  if pos > @farthest_pos
    @farthest_errors.clear
  end
  @farthest_pos = pos
  copy_stack = rule_stack.map{|pos, reason| Pegparse::ParserError.new(pos: pos, reason: reason) }
  copy_stack << Pegparse::ParserError.new(pos: pos, reason: reason)
  @farthest_errors << copy_stack
end