Tagging

.gitignore

@@ -1,2 +1,3 @@
 /luacov.*
-/site
+/site
+*.rbxlx

default.project.json

@@ -0,0 +1,45 @@
+{
+  "name": "roact",
+  "tree": {
+    "$className": "DataModel",
+    "ReplicatedStorage": {
+      "$className": "ReplicatedStorage",
+      "Roact": {
+        "$path": "lib"
+			},
+			"TestEZ": {
+				"$path": "modules/testez/lib"
+			}
+		},
+		"ServerScriptService": {
+			"$className": "ServerScriptService",
+			"RoactBenchmark": {
+				"$path": "benchmarks"
+			},
+			"RoactTests": {
+				"$path": "bin/run-tests.server.lua"
+			}
+		},
+		"StarterPlayer": {
+			"$className": "StarterPlayer",
+			"StarterPlayerScripts": {
+				"$className": "StarterPlayerScripts",
+				"RoactTestClient": {
+					"$path": "client"
+				},
+				"RoactExamples": {
+					"$path": "examples"
+				}
+			}
+		},
+    "HttpService": {
+      "$className": "HttpService",
+      "$properties": {
+        "HttpEnabled": {
+          "Type": "Bool",
+          "Value": true
+        }
+      }
+    }
+  }
+}

lib/PropMarkers/Tag.lua

@@ -0,0 +1,5 @@
+local Symbol = require(script.Parent.Parent.Symbol)
+
+local Tag = Symbol.named("Tag")
+
+return Tag

lib/RobloxRenderer.lua

@@ -4,12 +4,15 @@
 	renderer that does anything.
 ]]
 
+local CollectionService = game:GetService("CollectionService")
+
 local Binding = require(script.Parent.Binding)
 local Children = require(script.Parent.PropMarkers.Children)
 local ElementKind = require(script.Parent.ElementKind)
 local SingleEventManager = require(script.Parent.SingleEventManager)
 local getDefaultInstanceProperty = require(script.Parent.getDefaultInstanceProperty)
 local Ref = require(script.Parent.PropMarkers.Ref)
+local Tag = require(script.Parent.PropMarkers.Tag)
 local Type = require(script.Parent.Type)
 
 local applyPropsError = [[
@@ -90,8 +93,8 @@ local function applyProp(virtualNode, key, newValue, oldValue)
 		return
 	end
 
-	if key == Ref or key == Children then
-		-- Refs and children are handled in a separate pass
+	if key == Ref or key == Children or key == Tag then
+		-- Refs, children, and tags are handled in a separate pass
 		return
 	end
 
@@ -194,6 +197,10 @@ function RobloxRenderer.mountHostNode(reconciler, virtualNode)
 	virtualNode.hostObject = instance
 
 	applyRef(element.props[Ref], instance)
+
+	if element.props[Tag] ~= nil then
+		CollectionService:AddTag(instance, element.props[Tag])
+	end
 end
 
 function RobloxRenderer.unmountHostNode(reconciler, virtualNode)
@@ -220,6 +227,16 @@ function RobloxRenderer.updateHostNode(reconciler, virtualNode, newElement)
 		applyRef(newProps[Ref], virtualNode.hostObject)
 	end
 
+	if oldProps[Tag] ~= newProps[Tag] then
+		if oldProps[Tag] ~= nil then
+			CollectionService:RemoveTag(virtualNode.hostObject, oldProps[Tag])
+		end
+
+		if newProps[Tag] ~= nil then
+			CollectionService:AddTag(virtualNode.hostObject, newProps[Tag])
+		end
+	end
+
 	local success, errorMessage = pcall(updateProps, virtualNode, oldProps, newProps)
 
 	if not success then

lib/RobloxRenderer.spec.lua

@@ -1,4 +1,6 @@
 return function()
+	local CollectionService = game:GetService("CollectionService")
+
 	local assertDeepEqual = require(script.Parent.assertDeepEqual)
 	local Binding = require(script.Parent.Binding)
 	local Children = require(script.Parent.PropMarkers.Children)
@@ -11,6 +13,7 @@ return function()
 	local Logging = require(script.Parent.Logging)
 	local Portal = require(script.Parent.Portal)
 	local Ref = require(script.Parent.PropMarkers.Ref)
+	local Tag = require(script.Parent.PropMarkers.Tag)
 
 	local RobloxRenderer = require(script.Parent.RobloxRenderer)
 
@@ -736,4 +739,49 @@ return function()
 			})
 		end)
 	end)
+
+	describe("Tags", function()
+		it("should be assigned on mount", function()
+			local parent = Instance.new("Folder")
+			local ref = createRef()
+			local tag = "TestTag"
+
+			local element = createElement("Frame", {
+				[Tag] = tag,
+				[Ref] = ref,
+			})
+
+			local node = reconciler.createVirtualNode(element, parent, "Test")
+			RobloxRenderer.mountHostNode(reconciler, node)
+
+			expect(CollectionService:HasTag(ref.current, tag)).to.equal(true)
+		end)
+
+		it("should update properly", function()
+			local parent = Instance.new("Folder")
+			local ref = createRef()
+			local tagA = "TestTag"
+			local tagB = "OtherTag"
+
+			local element = createElement("Frame", {
+				[Tag] = tagA,
+				[Ref] = ref,
+			})
+
+			local node = reconciler.createVirtualNode(element, parent, "Test")
+			RobloxRenderer.mountHostNode(reconciler, node)
+
+			expect(CollectionService:HasTag(ref.current, tagA)).to.equal(true)
+
+			local newElement = createElement("Frame", {
+				[Tag] = tagB,
+				[Ref] = ref,
+			})
+
+			RobloxRenderer.updateHostNode(reconciler, node, newElement)
+
+			expect(CollectionService:HasTag(ref.current, tagA)).to.equal(false)
+			expect(CollectionService:HasTag(ref.current, tagB)).to.equal(true)
+		end)
+	end)
 end