From: Paul Battley <pbattley@...>
Date: 2006-07-30T02:46:24+09:00
Subject: Re: Wild ideas: Finding a missing 'end'

On 29/07/06, Mat Schaffer <schapht@gmail.com> wrote:
> This code generates a parse error at the last line.  Now most
> languages do this, so it's not a big deal.  But how frickin cool
> would it be if a future version of ruby looked at the indenting and
> made a guess as to where the missing end/} might be.

Like this?

---

def error_line(code)
  File.open('tmp.rb', 'w') do |io|
    io << code
  end
  s = `ruby -c tmp.rb 2>&1`
  if (s =~ /parse error/)
    return s[/\d+/].to_i
  else
    return false
  end
end

code = File.read(ARGV[0])

exit unless error_line(code)

lines = code.split(/\n/)

x = lines.length / 2
xmin = 0
xmax = lines.length

while l = error_line(code)
  if l < x
    xmax = x
  elsif l > x
    xmin = x
  else
    break
  end
  x = xmin + (xmax - xmin)/2
  code = (lines[0,x] + ['end'] + lines[x..-1]).join("\n")
end

puts("Error around line #{x+1}")

----

This is pretty rough code that I just threw together without much
thought, but it seems to work. Its temporary file handling leaves a
lot to be desired.

Paul.