Improve the formspec dev function

mods/apis/ctf_gui/dev.lua

@@ -1,31 +1,48 @@
+local unset_function = "[f]\nreturn "
+
 function ctf_gui.show_formspec_dev(player, formname, formspec, formcontext)
 	local filepath = minetest.get_worldpath().."/ctf_gui/"
 	local filename = filepath.."file_edit.txt"
+	local slower_loop = false
+
+	minetest.chat_send_all("Started formspec editing file at "..filename)
 
 	minetest.mkdir(filepath)
 
 	local file = assert(io.open(filename, "w"))
-
-	file:write(formspec)
-
+		if type(formspec) ~= "function" then
+			file:write(formspec)
+		else
+			file:write(unset_function)
+		end
 	file:close()
 
 	local function interval()
-		if formspec:sub(1, 3) == "[f]" then
-			local result, form = pcall(loadstring(formspec:sub(4)), formcontext)
-			ctf_gui.show_formspec(player, formname, result and form or "")
+		if type(formspec) == "function" then
+			ctf_gui.show_formspec(player, formname, formspec(formcontext))
+		elseif formspec:sub(1, 3) == "[f]" then
+			local result, form = pcall((loadstring(formspec:sub(4)) or function() return function() end end)(), formcontext)
+
+			ctf_gui.show_formspec(player, formname,
+				result and form or "size[10,10]hypertext[0,0;10,10;err;"..minetest.formspec_escape(form or "").."]"
+			)
+
+			slower_loop = not result
 		else
 			ctf_gui.show_formspec(player, formname, formspec)
 		end
 
-		minetest.after(1, function()
+		minetest.after(slower_loop and 3 or 1, function()
 			local f = assert(io.open(filename, "r"))
+			local new_form = f:read("*a")
 
-			formspec = f:read("*a")
+			if new_form ~= unset_function then
+				formspec = new_form
+			end
 
 			f:close()
 
-			if formspec:match("^exit") then
+			if type(formspec) == "function" or not formspec:match("^exit") then
 				interval()
 			else
 				minetest.request_shutdown("Formspec dev requested shutdown", true)