a filter that reformats the output of the TypeScript compiler e.g., `tsc -w *.ts --out /dev/null | coffee filter.coffee` so that it is more useful including source excerpts and little ansi colored arrows pointing to char, similar to the coffeescript compiler

tsc-filter.coffee

path = require 'path'
fs = require 'fs'

repeat = (s, n) -> r=''; r+=s while --n >= 0; r

process.stdin.setEncoding 'utf8'
process.stdin.resume()
buf = ''
parse = undefined
process.stdin.on 'data', (data) ->
  buf += data
  while (pos = buf.indexOf("\n")) isnt -1
    line = buf.substr 0, pos
    buf = buf.substr pos+1
    parse line

parse = (line) ->
  #console.log "line: ", line

  if m = line.match /^(.+)\((\d+),(\d+)\): error (TS\d+): (.+)$/
    [nil, absfile, ln, char, code, msg] = m
    file = path.relative process.cwd(), absfile
    fs.readFile absfile, encoding: 'utf8', (err, src) ->
      throw err if err
      src = src.replace(/\r\n/, "\n").split "\n"
      console.log "#{file}:#{ln}:#{char}: error: #{msg}"
      console.log "#{src[ln-1]}"
      process.stdout.write "#{Color.red}"
      process.stdout.write repeat "-", char-1
      process.stdout.write repeat "^", 1
      process.stdout.write "#{Color.reset}"
      process.stdout.write "\n"

Color =
  reset: "\u001b[0m"
  red:   "\u001b[31m"