feat: add detached, add more tests

pkgs/charm/benchmarks/effect.bench.luau

@@ -1,39 +0,0 @@
-local ReplicatedStorage = game:GetService("ReplicatedStorage")
-
-local Charm = require(ReplicatedStorage.Packages.Charm)
-
-local computed = Charm.computed
-local effect = Charm.effect
-local atom = Charm.atom
-
-return {
-	Functions = {
-		atom = function()
-			local state = atom(0)
-
-			effect(function()
-				state()
-			end)
-
-			for _ = 1, 500 do
-				state(math.random(1, 2))
-			end
-		end,
-
-		computed = function()
-			local state = atom(0)
-
-			local double = computed(function()
-				return 2 * state()
-			end)
-
-			effect(function()
-				double()
-			end)
-
-			for _ = 1, 500 do
-				state(math.random(1, 2))
-			end
-		end,
-	},
-}

pkgs/charm/benchmarks/mapped.bench.luau

@@ -0,0 +1,79 @@
+local ReplicatedStorage = game:GetService("ReplicatedStorage")
+
+local Charm = require(ReplicatedStorage.Packages.Charm)
+
+local atom = Charm.atom
+local computed = Charm.computed
+local mapped = Charm.mapped
+
+type Person = {
+	name: string,
+	age: number,
+}
+
+local personCount = 1000
+local initialState: { Person } = table.create(personCount)
+
+for i = 1, personCount do
+	initialState[i] = {
+		name = "Person " .. i,
+		age = math.random(1, 100),
+	}
+end
+
+local function mapper(person: Person): Person
+	return {
+		name = person.name .. "!",
+		age = person.age + 1,
+	}
+end
+
+local function simpleMapped(source: () -> { Person }): () -> { Person }
+	return computed(function()
+		local state = table.clone(source())
+		for index, person in state do
+			state[index] = mapper(person)
+		end
+		return state
+	end)
+end
+
+local function updatePercentageOfPeople(percent: number): ({ Person }) -> { Person }
+	return function(state)
+		local nextState = table.clone(state)
+		for index, person in state do
+			if math.random() < percent then
+				nextState[index] = mapper(person)
+			end
+		end
+		return nextState
+	end
+end
+
+return {
+	Functions = {
+		["mapped 50%"] = function(profiler)
+			profiler.Begin("init")
+			local src = atom(initialState)
+			local out = mapped(src, mapper)
+			out()
+			profiler.End()
+
+			profiler.Begin("update")
+			src(updatePercentageOfPeople(0.5))
+			profiler.End()
+		end,
+
+		["simple 50%"] = function(profiler)
+			profiler.Begin("init")
+			local src = atom(initialState)
+			local out = simpleMapped(src)
+			out()
+			profiler.End()
+
+			profiler.Begin("update")
+			src(updatePercentageOfPeople(0.5))
+			profiler.End()
+		end,
+	},
+}

pkgs/charm/src/effectScope.luau

@@ -3,13 +3,13 @@ local signals = require("./signals")
 local _effectScope = signals.effectScope
 local onScopeDispose = signals.onScopeDispose
 
-local function effectScope(callback: () -> ...() -> ()?): () -> ()
+local function effectScope(callback: () -> ...() -> ()?, detached: boolean?): () -> ()
 	return _effectScope(function()
 		local cleanup = callback()
 		if cleanup then
 			onScopeDispose(cleanup)
 		end
-	end)
+	end, detached)
 end
 
 return effectScope

pkgs/charm/src/observe.luau

@@ -1,59 +1,71 @@
 local signals = require("./signals")
 
-local computed = signals.computed
 local effect = signals.effect
+local effectScope = signals.effectScope
 local getCurrentSub = signals.getCurrentSub
 local onEffectCleanup = signals.onEffectCleanup
 local onScopeDispose = signals.onScopeDispose
-
-local function noop() end
+local pauseTracking = signals.pauseTracking
+local resumeTracking = signals.resumeTracking
 
 local function observe<K, V>(selector: () -> { [K]: V }, observer: (item: V, key: K) -> ...() -> ()?): () -> ()
-	local tracked = computed(function()
-		return selector()
-	end)
-
-	local cleanups: { [K]: () -> () } = {}
+	local scopes: { [K]: () -> () } = {}
 	local currentItems: { [K]: V } = {}
 
 	local function update(currentItems: { [K]: V }, previousItems: { [K]: V })
 		for key in previousItems do
-			local cleanup = cleanups[key]
-			if currentItems[key] == nil and cleanup then
-				cleanups[key] = nil
-				cleanup()
+			if currentItems[key] == nil then
+				local dispose = scopes[key]
+				scopes[key] = nil
+				dispose()
 			end
 		end
 
 		for key, value in currentItems do
 			if previousItems[key] == nil then
-				cleanups[key] = observer(value, key) or noop
+				scopes[key] = effectScope(function()
+					local cleanup = observer(value, key)
+					if cleanup then
+						onScopeDispose(cleanup)
+					end
+				end, true)
 			end
 		end
 	end
 
-	local function teardown()
-		for _, cleanup in cleanups do
-			cleanup()
+	local function disposeScopes()
+		for _, dispose in scopes do
+			dispose()
 		end
-		table.clear(cleanups)
+		table.clear(scopes)
 	end
 
 	local disposeEffect = effect(function()
+		local nextItems = selector()
+
+		if nextItems ~= currentItems then
 			local previousItems = currentItems
-		currentItems = tracked()
-		update(currentItems, previousItems)
+			currentItems = nextItems
+
+			pauseTracking()
+			local success, result: unknown = pcall(update, currentItems, previousItems)
+			resumeTracking()
+
+			if not success then
+				error(`observe() encountered an error: {result}`, 2)
+			end
+		end
 	end)
 
 	if getCurrentSub() then
-		onEffectCleanup(teardown)
+		onEffectCleanup(disposeScopes)
 	else
-		onScopeDispose(teardown)
+		onScopeDispose(disposeScopes)
 	end
 
 	return function()
 		disposeEffect()
-		teardown()
+		disposeScopes()
 	end
 end
 

pkgs/charm/src/signals.luau

@@ -352,11 +352,11 @@ local function effect(fn: () -> ()): () -> ()
 	return effectStop(e)
 end
 
-local function effectScope(fn: () -> ()): () -> ()
+local function effectScope(fn: () -> (), detached: boolean?): () -> ()
 	local e: EffectScope = {
 		flags = NONE,
 	}
-	if activeScope then
+	if activeScope and not detached then
 		link(e, activeScope)
 	end
 	local prev = setCurrentScope(e)

pkgs/charm/tests/gc.spec.luau

@@ -0,0 +1,72 @@
+local Charm = require("../src/lib")
+local suite = require("@tests/suite")
+
+local atom = Charm.atom
+local computed = Charm.computed
+local effect = Charm.effect
+local effectScope = Charm.effectScope
+local test = suite.test
+
+--- Creates a weak reference to a value.
+--- @return Function to dereference the value.
+local function weakRef<T>(value: T): () -> T?
+	local ref = setmetatable({ value = value }, { __mode = "v" })
+	return function()
+		return ref.value
+	end
+end
+
+--- Triggers garbage collection by allocating excessive memory.
+local function gc()
+	for _ = 1, 1000 do
+		local _ = table.create(100, 0)
+	end
+end
+
+--- In alien-signals, a computed value unlinks from dependencies when its last
+--- parent scope is disposed. Calling a computed value outside of a scope links
+--- it to dependencies, but the two-way link holds a strong reference to the
+--- computed value, so it won't GC until called in a scope and disposed.
+---
+--- This function releases a computed value by linking it to a scope and then
+--- immediately closing it, causing alien-signals to unlink the computed value
+--- and allow it to be garbage collected.
+local function release(getter: () -> ())
+	effectScope(function()
+		getter()
+	end)()
+end
+
+test("should release computed cache", function()
+	local srcRef = weakRef({})
+	local src = atom(srcRef())
+
+	local c = computed(function()
+		return src()
+	end)
+
+	c() -- cache src value
+	src(nil) -- release value
+	c = release(c) -- release computed
+
+	gc()
+	assert(srcRef() == nil, "should release computed cache")
+end)
+
+test("should not release effect for atom", function()
+	local effectCalls = 0
+	local src = atom(0)
+
+	effect(function()
+		effectCalls += 1
+		src()
+	end)
+
+	assert(effectCalls == 1, "should call effect once")
+
+	gc()
+	src(src() + 1)
+	assert(effectCalls == 2, "should call effect again")
+end)
+
+return {}

pkgs/charm/tests/listen.spec.luau

@@ -0,0 +1,29 @@
+local Charm = require("../src/lib")
+local suite = require("@tests/suite")
+
+local atom = Charm.atom
+local listen = Charm.listen
+local test = suite.test
+
+test("should listen to selector", function()
+	local source = atom(0)
+	local current, previous
+
+	local unsub = listen(function()
+		return source() + 1
+	end, function(a, b)
+		current = a
+		previous = b
+	end)
+
+	assert(current == 1 and previous == nil, "should run initially")
+	source(0)
+	assert(current == 1 and previous == nil, "should skip redundant update")
+	source(1)
+	assert(current == 2 and previous == 1, "should run with new value")
+	unsub()
+	source(2)
+	assert(current == 2 and previous == 1, "should not run after unsub")
+end)
+
+return {}

pkgs/charm/tests/observe.spec.luau

@@ -0,0 +1,64 @@
+local Charm = require("../src/lib")
+local suite = require("@tests/suite")
+
+local atom = Charm.atom
+local computed = Charm.computed
+local effect = Charm.effect
+local observe = Charm.observe
+local test = suite.test
+
+test("should observe items", function()
+	local items = atom({ 0, 0, 0 })
+	local updates = {}
+	local cleanups = {}
+
+	observe(items, function(_, key)
+		local get = computed(function()
+			return items()[key]
+		end)
+
+		effect(function()
+			table.insert(updates, get())
+		end)
+
+		return function()
+			table.insert(cleanups, key)
+		end
+	end)
+
+	assert(table.concat(updates) == "000", `bad mount: {table.concat(updates)}`)
+
+	table.clear(updates)
+	items({ 1, 2, 3 })
+	assert(table.concat(updates) == "123", `bad update: {table.concat(updates)}`)
+
+	table.clear(updates)
+	items({ 1, 2, nil :: any, 4 })
+	assert(table.concat(updates) == "4", `should add 4: {table.concat(updates)}`)
+	assert(table.concat(cleanups) == "3", `bad cleanup: {table.concat(cleanups)}`)
+end)
+
+test("should dispose scopes", function()
+	local items = atom({ 1, 2, 3 })
+	local a = atom(0)
+	local runs = {}
+
+	local dispose = observe(items, function(item)
+		effect(function()
+			table.insert(runs, item)
+			a()
+		end)
+	end)
+
+	table.clear(runs)
+	items({ 1, 2 })
+	a(1)
+	assert(table.concat(runs) == "12", `bad reruns: {table.concat(runs)}`)
+
+	table.clear(runs)
+	dispose()
+	a(2)
+	assert(table.concat(runs) == "", `should not rerun: {table.concat(runs)}`)
+end)
+
+return {}

pkgs/charm/tests/spec.luau

@@ -15,6 +15,9 @@ local function spec(name: string)
 end
 
 collect("signals")
+spec("gc")
 spec("subscribe")
+spec("listen")
+spec("observe")
 
 return {}

pkgs/charm/tests/subscribe.spec.luau

@@ -1,28 +1,58 @@
-local atom = require("../src/atom")
-local subscribe = require("../src/subscribe")
+local Charm = require("../src/lib")
 local suite = require("@tests/suite")
 
+type Atom<T> = Charm.Atom<T>
+
+local atom = Charm.atom
+local computed = Charm.computed
+local subscribe = Charm.subscribe
 local test = suite.test
 
-test("should subscribe to atom", function()
+test("should subscribe to selector", function()
 	local source = atom(0)
 	local current, previous
 
-	local unsub = subscribe(source, function(a, b)
+	local unsub = subscribe(function()
+		return source() + 1
+	end, function(a, b)
 		current = a
 		previous = b
 	end)
 
 	assert(not current and not previous, "should not run initially")
+	source(0)
+	assert(not current and not previous, "should skip redundant update")
 	source(1)
-	assert(current == 1, "should run with new value")
-	assert(previous == 0, "should run with old value")
-	source(2)
-	assert(current == 2, "should run with new value 2")
-	assert(previous == 1, "should run with old value 2")
+	assert(current == 2 and previous == 1, "should run with new value")
 	unsub()
-	source(3)
-	assert(current == 2, "should not run after unsubscribing")
+	source(2)
+	assert(current == 2 and previous == 1, "should not run after unsub")
+end)
+
+test("should ensure correct execution order", function()
+	local order = {}
+	local n1 = atom(0)
+	local n2 = atom(0)
+	local sum = computed(function()
+		return n1() + n2()
+	end)
+
+	subscribe(n1, function()
+		table.insert(order, 1)
+		n2(n2() + 1)
+	end)
+
+	subscribe(sum, function()
+		table.insert(order, 2)
+	end)
+
+	subscribe(n1, function()
+		table.insert(order, 3)
+	end)
+
+	n1(n1() + 1)
+
+	assert(table.concat(order) == "123", `bad order: {table.concat(order)}`)
 end)
 
 return {}