Added safer lhs writing:

Closes #127

Author: tyoeer

levelEditor/levelRoot.lua

@@ -19,6 +19,17 @@ function UI.loadErrorHandler(message)
 	local trace = fullTrace:sub(1,index-1)
 	MainUI:popup("Failed to load level!","Error message: "..message,trace)
 end
+function UI.saveErrorHandler(message)
+	message = tostring(message)
+	--part of snippet yoinked from default löve error handling
+	local fullTrace = debug.traceback("",2):gsub("\n[^\n]+$", "")
+	print(message)
+	print(fullTrace)
+	--cut of the part of the trace that goes into the code that calls UI:openEditor()
+	local index = fullTrace:find("%s+%[C%]: in function 'xpcall'")
+	local trace = fullTrace:sub(1,index-1)
+	return {message,trace}
+end
 
 function UI:initialize(levelPath, workshop)
 	self.workshop = workshop
@@ -68,9 +79,34 @@ end
 
 function UI:save()
 	if self:checkLimits("Can't save level:\n") then
-		self.levelFile:serializeAll(self.level)
-		self.latestHash = self.levelFile:writeAll()
-		MainUI:popup("Succesfully saved level!")
+		local success, hashOrErr = xpcall(
+			function()
+				self.levelFile:serializeAll(self.level)
+				return self.levelFile:writeWithBackup()
+			end,
+			self.saveErrorHandler
+		)
+		if success then
+			self.latestHash = hashOrErr
+			MainUI:popup("Succesfully saved level!")
+		else
+			local files = ""
+			for _,path in ipairs(self.levelFile.tempFiles) do
+				if files~="" then
+					files = files .. "\n"
+				end
+				files = files .. path
+			end
+			MainUI:popup(
+				"Error saving level:",
+				hashOrErr[1],
+				"\nLeft over files:",
+				files,
+				"\n",
+				hashOrErr[2]
+			)
+			return
+		end
 	end
 end
 

levelhead/lhs/init.lua

@@ -51,6 +51,8 @@ LHS.tags = {
 function LHS:initialize(path)
 	self:loadFile(path)
 	self.rawContentEntries = {}
+	--- Files created while writing
+	self.tempFiles = {}
 end
 
 --load the other files

levelhead/lhs/write.lua

@@ -159,11 +159,6 @@ end
 
 
 function LHS:writeAll()
-	local file = NFS.newFile(self.path)
-	local success,err = file:open("w")
-	if not success then error(err) end
-	self.saveHandle = file
-	
 	self:writeHeaders()
 
 	self:writeSingle("singleForeground")
@@ -181,11 +176,80 @@ function LHS:writeAll()
 	self:writeSingle("singleBackground")
 	self:writeStructure("backgroundRows")
 	self:writeStructure("backgroundColumns")
-	local hash = self:writeHash()
+	local hash =  self:writeHash()
+	return hash
+end
+
+function LHS:writeDirectly()
+	local file = NFS.newFile(self.path)
+	local success,err = file:open("w")
+	if not success then error(err) end
+	self.saveHandle = file
+	
+	local hash = self:writeAll()
 
 	self.saveHandle:close()
 	self.saveHandle = nil
 	return hash
 end
 
+function LHS:writeWithBackup()
+	local basePath, file = self.path:match("^(.+)[/\\]([^/\\]*)$")
+	if not basePath or not file then
+		error("Failed getting directory path", 2)
+	end
+	local r = string.format("%06i", love.math.random(0,999999))
+	local backupPath = basePath .. "/" .. "ch-backup-"..r.."-"..file
+	local _success, err = os.rename(self.path, backupPath)
+	if err then
+		error(string.format("Error moving\n%s\nto\n%s\n%s",self.path,backupPath,err),2)
+	end
+	table.insert(self.tempFiles, backupPath)
+	
+	local hash = self:writeDirectly()
+	
+	local checker = self.class:new(self.path)
+	local success, err = xpcall(function()
+		checker:readAll()
+	end, function(message)
+		message = tostring(message)
+		--part of snippet yoinked from default löve error handling
+		local fullTrace = debug.traceback("",2):gsub("\n[^\n]+$", "")
+		print(message)
+		print(fullTrace)
+		--cut of the part of the trace that goes into the code that calls UI:openEditor()
+		local index = fullTrace:find("%s+%[C%]: in function 'xpcall'")
+		local trace = fullTrace:sub(1,index-1)
+		return {message, trace}
+	end)
+	if not success then
+		error(string.format(
+			"Verification of written level failed: %s\nBackup of old level should live at: %s\n%s",
+			err[1],
+			backupPath,
+			err[2]
+		),2)
+	end
+	
+	local success, err = NFS.remove(backupPath)
+	if not success then
+		error(string.format(
+			"Error removing backup at %s:\n%s",
+			backupPath,
+			err
+		))
+	end
+	
+	local index = -1
+	for i,v in ipairs(self.tempFiles) do
+		if v==backupPath then
+			index = i
+			break
+		end
+	end
+	table.remove(self.tempFiles,index)
+	
+	return hash
+end
+
 return LHS