Much more robust reconciliation implementation

plugin/src/Plugin.lua

@@ -2,6 +2,7 @@ local Config = require(script.Parent.Config)
 local Http = require(script.Parent.Http)
 local Server = require(script.Parent.Server)
 local Promise = require(script.Parent.Promise)
+local Reconciler = require(script.Parent.Reconciler)
 
 local function collectMatch(source, pattern)
 	local result = {}
@@ -13,85 +14,6 @@ local function collectMatch(source, pattern)
 	return result
 end
 
-local function fileToName(filename)
-	if filename:find("%.server%.lua$") then
-		return filename:match("^(.-)%.server%.lua$"), "Script"
-	elseif filename:find("%.client%.lua$") then
-		return filename:match("^(.-)%.client%.lua$"), "LocalScript"
-	elseif filename:find("%.lua") then
-		return filename:match("^(.-)%.lua$"), "ModuleScript"
-	else
-		return filename, "StringValue"
-	end
-end
-
-local function nameToInstance(filename, contents)
-	local name, className = fileToName(filename)
-
-	local instance = Instance.new(className)
-	instance.Name = name
-
-	if className:find("Script$") then
-		instance.Source = contents
-	else
-		instance.Value = contents
-	end
-
-	return instance
-end
-
-local function make(item, name)
-	if item.type == "dir" then
-		local instance = Instance.new("Folder")
-		instance.Name = name
-
-		for childName, child in pairs(item.children) do
-			make(child, childName).Parent = instance
-		end
-
-		return instance
-	elseif item.type == "file" then
-		return nameToInstance(name, item.contents)
-	else
-		error("not implemented")
-	end
-end
-
-local function write(parent, route, item)
-	local location = parent
-
-	for index = 1, #route - 1 do
-		local piece = route[index]
-		local newLocation = location:FindFirstChild(piece)
-
-		if not newLocation then
-			newLocation = Instance.new("Folder")
-			newLocation.Name = piece
-			newLocation.Parent = location
-		end
-
-		location = newLocation
-	end
-
-	local fileName = route[#route]
-	local name = fileToName(fileName)
-
-	local existing = location:FindFirstChild(name)
-
-	local new
-	if item then
-		new = make(item, fileName)
-	end
-
-	if existing then
-		existing:Destroy()
-	end
-
-	if new then
-		new.Parent = location
-	end
-end
-
 local Plugin = {}
 Plugin.__index = Plugin
 
@@ -188,14 +110,14 @@ function Plugin:_pull(server, project, routes)
 		local route = routes[index]
 		local partitionName = route[1]
 		local partition = project.partitions[partitionName]
-		local data = items[index]
+		local item = items[index]
 
 		local fullRoute = collectMatch(partition.target, "[^.]+")
 		for i = 2, #route do
 			table.insert(fullRoute, routes[index][i])
 		end
 
-		write(game, fullRoute, data)
+		Reconciler.reconcileRoute(fullRoute, item)
 	end
 end
 

plugin/src/Reconciler.lua

@@ -0,0 +1,155 @@
+local Reconciler = {}
+
+local function itemToName(item, fileName)
+	if item and item.type == "dir" then
+		return fileName, "Folder"
+	elseif item and item.type == "file" or not item then
+		if fileName:find("%.server%.lua$") then
+			return fileName:match("^(.-)%.server%.lua$"), "Script"
+		elseif fileName:find("%.client%.lua$") then
+			return fileName:match("^(.-)%.client%.lua$"), "LocalScript"
+		elseif fileName:find("%.lua") then
+			return fileName:match("^(.-)%.lua$"), "ModuleScript"
+		else
+			return fileName, "StringValue"
+		end
+	else
+		error("unknown item type " .. tostring(item.type))
+	end
+end
+
+local function setValues(rbx, item, fileName)
+	local _, className = itemToName(item, fileName)
+
+	if className:find("Script") then
+		rbx.Source = item.contents
+	else
+		rbx.Value = item.contents
+	end
+end
+
+function Reconciler._reifyShallow(item, fileName)
+	if item.type == "dir" then
+		-- TODO: handle init
+		local rbx = Instance.new("Folder")
+		rbx.Name = fileName
+
+		return rbx
+	elseif item.type == "file" then
+		local objectName, className = itemToName(item, fileName)
+
+		local rbx = Instance.new(className)
+		rbx.Name = objectName
+
+		setValues(rbx, item, fileName)
+
+		return rbx
+	else
+		error("unknown item type " .. tostring(item.type))
+	end
+end
+
+function Reconciler._reify(item, fileName)
+	local rbx = Reconciler._reifyShallow(item, fileName)
+
+	if item.type == "dir" then
+		for childName, child in pairs(item.children) do
+			local childRbx = Reconciler._reify(child, childName)
+			childRbx.Parent = rbx
+
+			-- TODO: handle init
+		end
+	end
+
+	return rbx
+end
+
+function Reconciler.reconcile(rbx, item, fileName)
+	-- Item was deleted!
+	if not item then
+		if rbx then
+			rbx:Destroy()
+		end
+
+		return
+	end
+
+	-- Item was created!
+	if not rbx then
+		return Reconciler._reify(item, fileName)
+	end
+
+	if item.type == "dir" then
+		-- TODO: handle init
+
+		if rbx.ClassName ~= "Folder" then
+			return Reconciler._reify(item, fileName)
+		end
+
+		local visitedChildren = {}
+
+		for childFileName, childItem in pairs(item.children) do
+			local childName = itemToName(childItem, childFileName)
+
+			visitedChildren[childName] = true
+
+			Reconciler.reconcile(rbx:FindFirstChild(childName), childItem, childFileName)
+		end
+
+		for _, childRbx in ipairs(rbx:GetChildren()) do
+			-- Child was deleted!
+			if not visitedChildren[childRbx.Name] then
+				Reconciler.reconcile(childRbx, nil, nil)
+			end
+		end
+
+		return rbx
+	elseif item.type == "file" then
+		local _, className = itemToName(item, fileName)
+
+		if rbx.ClassName ~= className then
+			return Reconciler._reify(item, fileName)
+		end
+
+		setValues(rbx, item, fileName)
+
+		return rbx
+	else
+		error("unknown item type " .. tostring(item.type))
+	end
+end
+
+function Reconciler.reconcileRoute(route, item)
+	local location = game
+
+	for i = 1, #route - 1 do
+		local piece = route[i]
+		local newLocation = location:FindFirstChild(piece)
+
+		if not newLocation then
+			newLocation = Instance.new("Folder")
+			newLocation.Name = piece
+			newLocation.Parent = location
+		end
+
+		location = newLocation
+	end
+
+	local fileName = route[#route]
+
+	local name = itemToName(item, fileName)
+	local rbx = location:FindFirstChild(name)
+	local newRbx = Reconciler.reconcile(rbx, item, fileName)
+
+	if newRbx ~= rbx then
+		if rbx then
+			rbx:Destroy()
+		end
+
+		if newRbx then
+			newRbx.Parent = location
+		end
+	end
+end
+
+return Reconciler