LÖVE Error handler and Notepad++

errors.lua

--No credit nor license is required for this function
--It is based on the original code by LÖVE developers
--Just minor functionality was added, if at all.

return function (src)
	local dir = string.gsub(src,"([\\])","/")
	local src = dir:match("/$") and dir or (dir.."/")

	function love.errhand(msg)
		msg = tostring(msg)

		print("Error:")
		print(debug.traceback(tostring(msg), 3):gsub("\n[^\n]+$", ""))

		local j = string.gsub(msg,"^(Syntax error: )","")
		local t = {}

		for i=1,2 do
			local pos1, pos2 = string.find(j,":", 1, true)
			if not pos1 then
				t[#t + 1] = j
				break
			end
			t[#t + 1] = string.sub(j, 1, pos1 - 1)
			j = string.sub(j, pos2 + 1)
		end

		if string.match(t[1] or "","^%[.+%]$") then
			print("The error is in the internal function: "..(t[1] or ""))
		else
			local f,l = ((src or "")..t[1] or ""),t[2] or ""
			print (string.format("FILE = %s, LINE = %s",f,l))
		end

		if not love.window or not love.graphics or not love.event then
			return
		end

		if not love.graphics.isCreated() or not love.window.isCreated() then
			if not pcall(love.window.setMode, 800, 600) then
				return
			end
		end

		if love.mouse then
			love.mouse.setVisible(true)
			love.mouse.setGrabbed(false)
		end
		if love.joystick then
			for i,v in ipairs(love.joystick.getJoysticks()) do
				v:setVibration()
			end
		end
		if love.audio then love.audio.stop() end

		local pxs = love.window.getPixelScale and love.window.getPixelScale() or 1

		love.graphics.reset()
		local font = love.graphics.setNewFont(math.floor(14 * pxs))

		local sRGB = select(3, love.window.getMode()).srgb

		if sRGB then
			love.graphics.setBackgroundColor(love.math.gammaToLinear(89, 157, 220))
		else
			love.graphics.setBackgroundColor(89, 157, 220)
		end

		love.graphics.setColor(255, 255, 255, 255)
		local trace = debug.traceback()
		love.graphics.clear()
		love.graphics.origin()

		local err = {}

		table.insert(err, "Error\n")
		table.insert(err, msg.."\n\n")

		for l in string.gmatch(trace, "(.-)\n") do
			if not string.match(l, "boot.lua") then
				l = string.gsub(l, "stack traceback:", "Traceback\n")
				table.insert(err, l)
			end
		end

		local p = table.concat(err, "\n")
		p = string.gsub(p, "\t", "")
		p = string.gsub(p, "%[string \"(.-)\"%]", "%1")

		local function draw()
			local pos = 70 * pxs
			love.graphics.clear()
			love.graphics.printf(p, pos, pos, love.graphics.getWidth() - pos)
			love.graphics.present()
		end

		while true do
			love.event.pump()
			for e, a, b, c in love.event.poll() do
				if e == "quit" then
					return
				end
				if e == "keypressed" and a == "escape" then
					return
				end
			end

			draw()

			if love.timer then
				love.timer.sleep(0.1)
			end
		end
	end
end

lurker.lua

--1
-- Modified version of lurker 
-- Changes:
--		Doesnt depend on Lume
--		Better error message (now with the FILE and LINE) 
--		Draw function can be easily changed
--		Stops all the stuff that can be annoying to the user
--		Works better when sRGB or HighDPI is enabled
--		Less stuff printed to the console (because that can turn to be annoying)
--		More callbacks supported
--
-- Copyright (c) 2015 rxi
--
-- This library is free software; you can redistribute it and/or modify it
-- under the terms of the MIT license. See LICENSE for details.

local lurker = { _version = "1.0.1" }

local lovecallbacknames = {
	"update",
	"load",
	"draw",
	"mousepressed",
	"mousereleased",
	"keypressed",
	"keyreleased",
	"focus",
	"quit",
}

function lurker.init(src)
	local src = string.gsub(src,"([\\])","/")
	lurker.src = src:match("/$") and src or (src.."/")
	lurker.path = "."
	lurker.preswap = function() end
	lurker.postswap = function() end
	lurker.interval = .5
	lurker.protected = true
	lurker.quiet = false
	lurker.lastscan = 0
	lurker.lasterrorfile = nil
	lurker.files = {}
	lurker.funcwrappers = {}
	lurker.lovefuncs = {}
	lurker.state = "init"
	for _, v in ipairs(lurker.getchanged()) do lurker.resetfile(v) end
	return lurker
end

function lurker.listdir(path, recursive, skipdotfiles, t)
	path = (path == ".") and "" or path
	local function fullpath(x) return path .. "/" .. x end
	local t = {}
	for _, f in ipairs(love.filesystem.getDirectoryItems(path)) do
		local f = fullpath(f)
		if not skipdotfiles or not f:match("/%.[^/]*$") then
			if recursive and love.filesystem.isDirectory(f) then
				lurker.listdir(f, true, skipdotfiles, t)
			else
				table.insert(t, f:match("^[/]*(.-)[/]*$"))
			end
		end
	end
	return t
end

function lurker.initwrappers()
	for _, v in pairs(lovecallbacknames) do
		lurker.funcwrappers[v] = function(...)
			local args = {...}
			xpcall(function()
				return lurker.lovefuncs[v] and lurker.lovefuncs[v](unpack(args))
			end, lurker.onerror)
		end
		lurker.lovefuncs[v] = love[v]
	end
	lurker.updatewrappers()
end

function lurker.updatewrappers()
	for _, v in pairs(lovecallbacknames) do
		if love[v] ~= lurker.funcwrappers[v] then
			lurker.lovefuncs[v] = love[v]
			love[v] = lurker.funcwrappers[v]
		end
	end
end

function lurker.draw ()
	local sRGB = select(3, love.window.getMode()).srgb

	if sRGB then
		love.graphics.setBackgroundColor(love.math.gammaToLinear(89, 157, 220))
	else
		love.graphics.setBackgroundColor(89, 157, 220)
	end

	love.graphics.setColor(255, 255, 255, 255)

	local pxs = love.window.getPixelScale and love.window.getPixelScale() or 1
	local pos = 70 * pxs
	love.graphics.printf(lurker.errmsg, pos, pos, love.graphics.getWidth() - pos*2)
end

function lurker.onerror(e, nostacktrace)
	lurker.state = "error"

	-- Set up callbacks
	for _, v in pairs(lovecallbacknames) do
		love[v] = function() end
	end

	msg = tostring(e)

	print("Error:")
	print(debug.traceback(msg, 2):gsub("\n[^\n]+$", ""))

	local j = string.gsub(msg,"^(Syntax error: )","")
	local t = {}

	for i=1, 2 do
		local pos1, pos2 = string.find(j,":", 1, true)
		if not pos1 then
			t[#t + 1] = j
			break
		end
		t[#t + 1] = string.sub(j, 1, pos1 - 1)
		j = string.sub(j, pos2 + 1)
	end

	if string.match(t[1] or "","^%[.+%]$") then
		print("The error is in the internal function: "..(t[1] or ""))
	else
		local f,l = ((lurker.src or "")..t[1] or ""),t[2] or ""
		print (string.format("FILE = %s, LINE = %s",f,l))
	end

	if not love.window or not love.graphics or not love.event then
		love.event.quit()
	end

	if not love.graphics.isCreated() or not love.window.isCreated() then
		if not pcall(love.window.setMode, 800, 600) then
			love.event.quit()
		end
	end

	if love.mouse then
		love.mouse.setVisible(true)
		love.mouse.setGrabbed(false)
	end

	if love.joystick then
		for i,v in ipairs(love.joystick.getJoysticks()) do
			v:setVibration()
		end
	end
	if love.audio then love.audio.stop() end

	local err = {}

	table.insert(err, "Error\n")
	table.insert(err, msg.."\n\n")

	local trace = debug.traceback()
	for l in string.gmatch(trace, "(.-)\n") do
		if not string.match(l, "boot.lua") then
			l = string.gsub(l, "stack traceback:", "Traceback\n")
			table.insert(err, l)
		end
	end

	lurker.errmsg = table.concat(err, "\n")
	lurker.errmsg = string.gsub(lurker.errmsg, "\t", "")
	lurker.errmsg = string.gsub(lurker.errmsg, "%[string \"(.-)\"%]", "%1")

	local pxs = love.window.getPixelScale and love.window.getPixelScale() or 1
	local font = love.graphics.setNewFont(math.ceil(14 * pxs))

	love.draw = lurker.draw or function () end

	love.graphics.push("all") --Go back to default settings but save old ones
	love.graphics.reset()
	love.update = lurker.update

	love.keypressed = function(k)
		if k == "escape" then
			love.event.quit()
		end
	end
end

function lurker.exitinitstate()
	lurker.state = "normal"
	if lurker.protected then
		lurker.initwrappers()
	end
end

function lurker.exiterrorstate()
	lurker.state = "normal"
	for _, v in pairs(lovecallbacknames) do
		love[v] = lurker.funcwrappers[v]
	end
	love.graphics.pop()
end

function lurker.update() 
	if lurker.state == "init" then
		lurker.exitinitstate()
	end
	local diff = love.timer.getTime() - lurker.lastscan
	if diff > lurker.interval then
		lurker.lastscan = lurker.lastscan + diff
		local changed = lurker.scan()
		if #changed > 0 and lurker.lasterrorfile then
			local f = lurker.lasterrorfile
			lurker.lasterrorfile = nil
			lurker.hotswapfile(f)
		end
	end
end

function lurker.getchanged()
	local function fn(f)
		return f:match("%.lua$") and lurker.files[f] ~= love.filesystem.getLastModified(f)
	end

	local t = lurker.listdir(lurker.path, true, true)

	local rtn = {}

	for k, v in ipairs(t) do
		if fn(v) then rtn[#rtn + 1] = v end
	end

	return rtn
end

function lurker.modname(f)
	return (f:gsub("%.lua$", ""):gsub("[/\\]", "."))
end

function lurker.resetfile(f)
	lurker.files[f] = love.filesystem.getLastModified(f)
end

function lurker.hotswapfile(f)
	if lurker.state == "error" then 
		lurker.exiterrorstate()
	end
	if lurker.preswap(f) then
		lurker.resetfile(f)
		return
	end
	local modname = lurker.modname(f)
	local oldglobal = {}
	for k, v in pairs(_G) do oldglobal[k] = v end
	local updated = {}
	local function update(old, new)
		if updated[old] then return end
		updated[old] = true
		local oldmt, newmt = getmetatable(old), getmetatable(new)
		if oldmt and newmt then update(oldmt, newmt) end
		for k, v in pairs(new) do
			if type(v) == "table" then update(old[k], v) else old[k] = v end
		end
	end
	local err = nil
	local function onerror(e)
		for k, v in pairs(_G) do _G[k] = oldglobal[k] end
		err = e
	end
	local ok, oldmod = pcall(require, modname)
	oldmod = ok and oldmod or nil
	xpcall(function()
		package.loaded[modname] = nil
		local newmod = require(modname)
		if type(oldmod) == "table" then update(oldmod, newmod) end
		for k, v in pairs(oldglobal) do
			if v ~= _G[k] and type(v) == "table" then
				update(v, _G[k])
				_G[k] = v
			end
		end
	end, onerror)
	package.loaded[modname] = oldmod
	if err then
		if not lurker.quiet and lurker.protected then
			lurker.lasterrorfile = f
			lurker.onerror(err, true)
			lurker.resetfile(f)
			return
		end
	end
	lurker.resetfile(f)
	lurker.postswap(f)
	if lurker.protected then
		lurker.updatewrappers()
	end
end

function lurker.scan()
	if lurker.state == "init" then
		lurker.exitinitstate()
	end
	local changed = lurker.getchanged()
	for _, v in ipairs(changed) do lurker.hotswapfile(v) end
	return changed
end

return setmetatable(lurker,{__call = function(self,...) return self.init(...) end})

Description

This is an error handler for LÖVE, it does the same thing as the standard error handler, but adds a line to the error description printed to the console.

This extra line is useful to determine where the error is present, and it has this format :

FILE = C:/path/to the/error/file.lua, LINE = n

This, in turn, can be used with Notepad++ Plugin NppExec to add a link that will take you to that place

Including this error handler in your code

To use this error handler you need to require it in your main.lua, like this:

io.stdout:setvbuf("no") -- Print to Notepad++ console
love.load = function (args)
    require "errors" (args[1])
end

Configuring N++

Install NppExec plugin in Notepad++ and add this Filter to Console Output Filters... > Highlight

FILE = %ABSFILE%, LINE = %LINE%

You'll need to open the file with NppExec to get the output to the console. There are some problems opening LÖVE directly from NppExec, so we instead call it from a .bat file, called run.bat, with the following code:

@echo off
:: Your LÖVE installation here
cd "C:\Program Files\Love 0.9.1\"
:there
    if %1 neq "" goto here
    echo No file found
    goto end
:more
    if "%1" neq "" goto here
    goto end
:here
    call love.exe %1
    shift
    goto more
:end
    exit

To run this bat configure this command in NppExec and save it as Love (NPP_SAVEALL is not mandatory)

NPP_SAVEALL
"C:\path\to\run.bat" "$(CURRENT_DIRECTORY)"

Then in Plugin > NppExec > Advance Options > Menu Item Add an Item called Love that triggers the Love command.

After that go to Execute > Modify Shortcuts / Delete Commands > Plugin Command and add a key shortcut to this command, I prefer CTRL + L

Problems

• LÖVE can't handle two consoles at the same time, that is why even if in your conf.lua you define t.console = true the console will never be spawn, even then, you can still get the console output in the NppExec console.
• If you add more filters the file may be detected incorrectly, try to keep your filters down. Also, this filter should be always the first one, or others will take precedence instead of this one.

PS: It also fix the errors in HighDPI screens like Mac OS X Retina Displays and a bug in the color when in sRGB mode. This bugs where fixed in 0.9.2, but this file works in all 0.9.X versions.

If you use strong or a similar library in your project, you can replace this:

for i=1,2 do
    local pos1, pos2 = string.find(j,":", 1, true)
    if not pos1 then
        t[#t + 1] = j
        break
    end
    t[#t + 1] = string.sub(j, 1, pos1 - 1)
    j = string.sub(j, pos2 + 1)
end 

with this:

t = string.split(j,":",false) --False because it's not a pattern

Strong also supports this:

t = j / ":"