Textadept: Check Python syntax after saving.

python_syntax_check.lua

events.connect('file_after_save',
  function() -- shows all Python errors as annotations
    if buffer:get_lexer() == 'python' then
      local lfs = require 'lfs'
      local buffer = buffer
      buffer:annotation_clear_all()
      local filepath = buffer.filename:iconv(_CHARSET, 'UTF-8')
      local filedir, filename = '', filepath
      if filepath:find('[/\\]') then
        filedir, filename = filepath:match('^(.+[/\\])([^/\\]+)$')
      end
      local current_dir = lfs.currentdir()
      lfs.chdir(filedir)
      local command = 'flake8 ' .. filedir .. filename
      local p = io.popen(command..' 2>&1')
      mylines = p:read("*a")
      p:close()
      line_end = string.find(mylines, "\n")
      while line_end and mylines do
        out, mylines = string.sub(mylines, 0, line_end), string.sub(mylines, line_end + 1)
        lfs.chdir(current_dir)
        local line, err_type, err_msg =
          string.match(out, "(%d+):%d+: ([A-Z]%d%d%d) (.*)$")
        line = tonumber(line)
        if line and not buffer.annotation_text[line - 1] then
          buffer.annotation_visible = buffer.ANNOTATION_BOXED
          buffer.annotation_text[line - 1] = err_type .. ":" .. err_msg
          buffer.annotation_style[line - 1] = 8 -- error style number
          buffer:goto_line(line - 1)
        elseif line then
          buffer.annotation_text[line - 1] =  buffer.annotation_text[line - 1] .. err_type .. ":" .. err_msg
          buffer.annotation_style[line - 1] = 8 -- error style number
        end
        line_end = string.find(mylines, "\n")
      end
    end
  end)

fixed to work with current Text Adept API and use flake8 for style and syntax checks

Shows all errors not just the first one.

Fixed off by one error because of how textadept and python number lines.

Handles more than 1 error per line.