-- This module provides a library for formatting file wikilinks.  local yesno = require('Module:Yesno') local checkType = require('libraryUtil').checkType  local p = {}  function p._main(args)  checkType('_main', 1, args, 'table')   -- This is basically libraryUtil.checkTypeForNamedArg, but we are rolling our  -- own function to get the right error level.  local function checkArg(key, val, level)  if type(val) ~= 'string' then  error(string.format(  "type error in '%s' parameter of '_main' (expected string, got %s)",  key, type(val)  ), level)  end  end   local ret = {}   -- Adds a positional parameter to the buffer.  local function addPositional(key)  local val = args[key]  if not val then  return nil  end  checkArg(key, val, 4)  ret[#ret + 1] = val  end   -- Adds a named parameter to the buffer. We assume that the parameter name  -- is the same as the argument key.  local function addNamed(key)  local val = args[key]  if not val then  return nil  end  checkArg(key, val, 4)  ret[#ret + 1] = key .. '=' .. val  end   -- Filename  checkArg('file', args.file, 3)  ret[#ret + 1] = 'File:' .. args.file   -- Format  if args.format then  checkArg('format', args.format)  if args.formatfile then  checkArg('formatfile', args.formatfile)  ret[#ret + 1] = args.format .. '=' .. args.formatfile  else  ret[#ret + 1] = args.format  end  end   -- Border  if yesno(args.border) then  ret[#ret + 1] = 'border'  end   addPositional('location')  addPositional('alignment')  addPositional('size')  addNamed('upright')  addNamed('link')  addNamed('alt')  addNamed('page')  addNamed('class')  addNamed('lang')  addNamed('start')  addNamed('end')  addNamed('thumbtime')  addPositional('caption')   return string.format('[[%s]]', table.concat(ret, '|')) end  function p.main(frame)  local origArgs = require('Module:Arguments').getArgs(frame, {  wrappers = 'Template:File link'  })  if not origArgs.file then  error("'file' parameter missing from [[Template:File link]]", 0)  end   -- Copy the arguments that were passed to a new table to avoid looking up  -- every possible parameter in the frame object.  local args = {}  for k, v in pairs(origArgs) do  -- Make _BLANK a special argument to add a blank parameter. For use in  -- conditional templates etc. it is useful for blank arguments to be  -- ignored, but we still need a way to specify them so that we can do  -- things like [[File:Example.png|link=]].  if v == '_BLANK' then  v = ''  end  args[k] = v  end  return p._main(args) end  return p