test: add benchmarks, dev mode

src/__tests__/benchmarks/atom.bench.luau

@@ -0,0 +1,53 @@
+-- This file is for use by Benchmarker
+-- https://boatbomber.itch.io/benchmarker
+
+local Package = game:GetService("ReplicatedStorage").Packages.charm
+
+local atom = require(Package.atom)
+local derive = require(Package.derive)
+
+return {
+	ParameterGenerator = function()
+		return atom({ count = 0 })
+	end,
+
+	Functions = {
+		atom = function(_, source: any)
+			for _ = 1, 500 do
+				source({ count = math.random(1, 2) })
+			end
+		end,
+
+		derived = function(_, source: any)
+			derive(source, function(state)
+				return { count = 2 * state.count }
+			end)
+			for _ = 1, 500 do
+				source({ count = math.random(1, 2) })
+			end
+		end,
+
+		derived_memo = function(_, source: any)
+			source:memo(function(previous, current)
+				return previous.count == current.count
+			end)
+			derive(source, function(state)
+				return { count = 2 * state.count }
+			end)
+			for _ = 1, 500 do
+				source({ count = math.random(1, 2) })
+			end
+		end,
+
+		derived_writable = function(_, source: any)
+			local derived = derive(source, function(state)
+				return { count = 2 * state.count }
+			end):writable(function(update)
+				source({ count = 0.5 * update.count })
+			end)
+			for _ = 1, 500 do
+				derived({ count = 2 * math.random(1, 2) })
+			end
+		end,
+	},
+}

src/__tests__/derive.spec.luau

@@ -89,4 +89,14 @@ return function()
 
 		error("None of the derived atoms were collected")
 	end)
+
+	it("unmounts from parent atom", function()
+		local source = atom(1)
+		local derived = derive(source, function(value)
+			return value
+		end)
+		expect((next(source.listeners))).to.be.ok()
+		derived:unmount()
+		expect((next(source.listeners))).to.never.be.ok()
+	end)
 end

src/__tests__/init.spec.luau

@@ -1,6 +1,16 @@
 local reference = require(script.Parent.Parent.utils.reference)
 
 return function()
+	local previous = _G.__DEV__
+
+	beforeAll(function()
+		_G.__DEV__ = true
+	end)
+
+	afterAll(function()
+		_G.__DEV__ = previous
+	end)
+
 	afterEach(function()
 		reference.clear()
 	end)

src/__tests__/react/init.spec.luau

@@ -2,7 +2,7 @@ return function()
 	local previous = _G.__DEV__
 
 	beforeAll(function()
-		_G.__DEV__ = true
+		_G.__DEV__ = false -- prevent React errors
 	end)
 
 	afterAll(function()

src/atom.luau

@@ -1,15 +1,10 @@
 local reference = require(script.Parent.utils.reference)
 
 type AtomInternal<T> = {
-	--- @deprecated
 	setForced: (self: AtomInternal<T>, state: T | ((T) -> T)) -> (),
-	--- @deprecated
 	listeners: { [(T) -> ()]: true },
-	--- @deprecated
 	debugTraceback: string,
-	--- @deprecated
 	debugLabel: string,
-	--- @deprecated
 	owners: { [any]: true },
 }
 
@@ -63,10 +58,10 @@ local function atom<State>(state: State): Atom<State>
 		if setter then
 			local result = setter(nextState, state)
 
-			if result == nil then
+			if result ~= nil then
-				return
-			else
 				nextState = result
+			else
+				return
 			end
 		end
 
@@ -103,7 +98,9 @@ local function atom<State>(state: State): Atom<State>
 
 	function atom:readonly(): ReadonlyAtom<State>
 		function setter(_, _)
-			error(`Attempt to set read-only atom '{label}' created at: {traceback}`, 3)
+			if _G.__DEV__ then
+				error(`Attempt to set read-only atom '{label}' created at: {traceback}`, 3)
+			end
 		end
 		return self
 	end

src/derive.luau

@@ -15,16 +15,29 @@ type Derive =
 local function derive<Result>(...): ReadonlyAtom<Result>
 	local atoms: { Atom<unknown> } = { ... }
 	local combiner: (...unknown) -> Result = table.remove(atoms) :: any
-	local size = #atoms
+	local size = 0
 	local dependencies: { unknown } = {}
+	local listeners: { [() -> ()]: boolean } = {}
 
 	for index, atom in atoms do
 		dependencies[index] = atom:get()
+		size += 1
 	end
 
 	local derivedAtom = atom(combiner(table.unpack(dependencies, 1, size))):readonly()
+	local derivedAtomUnmount = derivedAtom.unmount
 	local getDerivedAtom = reference.weak(derivedAtom)
 
+	function derivedAtom:unmount()
+		derivedAtomUnmount(self)
+
+		for listener in listeners do
+			for _, atom in atoms do
+				atom.listeners[listener] = nil
+			end
+		end
+	end
+
 	for index, atom in atoms do
 		local function listener(state: unknown)
 			-- Remove the listener if the derived atom has been garbage collected,
@@ -44,6 +57,7 @@ local function derive<Result>(...): ReadonlyAtom<Result>
 		-- its derived atoms will be in use as well.
 		derivedAtom.owners[atom] = true
 		atom.listeners[listener] = true
+		listeners[listener] = true
 	end
 
 	return derivedAtom