src/apply.luau

@@ -138,7 +138,7 @@ local function apply<T>(instance: T & Instance, properties: { [unknown]: unknown
     -- finally set parent if any
     if parent then
         if type(parent) == "function" then
-            error("cannot set parent to state")
+            bind.parent(instance, parent :: () -> ())
         else
             instance.Parent = parent :: Instance
         end

src/bind.luau

@@ -6,10 +6,11 @@ local flags = require(script.Parent.flags)
 local graph = require(script.Parent.graph)
 type Node<T> = graph.Node<T>
 local create_node = graph.create_node
+local get_scope = graph.get_scope
 local open_scope = graph.open_scope
 local close_scope = graph.close_scope
+local track = graph.track
 local add_child = graph.add_child
-local capture_parents = graph.capture_parents
 
 --[[
 
@@ -70,9 +71,13 @@ function bind(instance: Instance, property: string, setter: (Instance) -> ())
     local binding = create_node(instance)
     binding.effect = setter
 
-    open_scope(binding.scope)
+    local owner = get_scope()
+    assert(owner)
 
-    capture_parents(binding, setter :: () -> any, instance)
+    open_scope(binding)
+    track(owner)
+
+    setter(instance)
 
     close_scope()
 end
@@ -84,12 +89,7 @@ local function bind_property(instance: Instance, property: string, fn: () -> unk
 end
 
 local function bind_parent(instance: Instance, fn: () -> Instance?)
-    instance.Destroying:Connect(function()
-        instance = nil :: any -- allow gc when destroyed
-    end)
-
     bind(instance, "Parent", function(instance)
-        local _ = instance -- state will strongly reference instance when parent is bound
         instance.Parent = fn()    
     end)
 end

src/derive.luau

@@ -2,7 +2,6 @@ if not game then script = require "test/relative-string" end
 
 local graph = require(script.Parent.graph)
 local create_node = graph.create_node
-local capture_parents = graph.capture_parents
 local add_child = graph.add_child
 local update = graph.update
 local track = graph.track
@@ -11,17 +10,19 @@ local open_scope = graph.open_scope
 local close_scope = graph.close_scope
 
 local function derive<T>(fn: () -> T): () -> T
-    assert(get_scope())
+    local owner = get_scope()
+    assert(owner)
 
     local node = create_node((false :: any) :: T)
     node.effect = function()
         node.cache = fn()
-        update(node)
     end
 
-    open_scope(node.scope)
+    add_child(owner, node)
 
-    node.cache = capture_parents(node, fn)
+    open_scope(node)
+
+    node.cache = fn()
 
     close_scope()
 

src/graph.luau

@@ -11,13 +11,16 @@ export type StartNode<T> = {
 export type Node<T> =  {
     cache: T,
     children: { [Node<T>]: true } | false,
-    effect:  (T) -> (),
+    effect:  (T) -> () | false,
     cleanups: { () -> () } | false,
 }
 
+local active = {} :: { [Node<any>]: true }
+
 local scopes = { n = 0 } :: { [number]: Node<any>, n: number }
 
 local WEAK_VALUES = { __mode = "v" }
+local WEAK_KEYS = { __mode = "k" }
 local EVALUATION_ERR = "error while evaluating source:\n\n"
 
 -- runs a given callback in a context that Luau does not allow yielding in
@@ -46,34 +49,27 @@ local check_for_yield: <T...>(fn: (T...) -> unknown, T...) -> () do
     end
 end
 
-local function get_scope(): Node<unknown>
+local function get_stack_scope(offset: number): Node<unknown>?
+    return scopes[scopes.n - offset]
+end
+
+local function get_scope(): Node<unknown>?
     return scopes[scopes.n]
 end
 
-local function add_child<T>(parent: Node<any>, child: Node<any>)
+local function add_child<T>(parent: StartNode<any>, child: Node<any>)
     if parent.children then
         parent.children[child] = true
     else
         parent.children = { [child] = true :: true }
+        setmetatable(parent.children :: any, WEAK_KEYS) -- todo:
     end
 end
 
--- local function open_root_scope<T>(node: Node<T>)
---     assert(not scopes[1])
-
---     local n = scopes.n + 1
---     scopes.n = n
---     scopes[n] = node
--- end
-
 local function open_scope<T>(node: Node<T>)
     local n = scopes.n + 1
     scopes.n = n
     scopes[n] = node
-
-    -- local parent = scopes[n-1]
-    -- assert(parent)
-    -- add_child(parent, node)
 end
 
 local function close_scope()
@@ -100,49 +96,71 @@ local function run_cleanups<T>(node: Node<T>)
 end
 
 local function run_effect<T>(node: Node<T>)
+    if node.effect then
         node.effect(node.cache)
     end
+end
 
 local function destroy<T>(node: Node<T>)
     run_cleanups(node)
-    for _, child in ipairs(node) do
+    active[node] = nil
+    if node.children then
+        for child in node.children do
             destroy(child)
         end
     end
+end
 
 
 -- runs node effects, recalculates descendants and runs descendant effects
-local function update<T>(node: StartNode<T>)
+local function rec<T>(node: StartNode<T>, update_queue: { Node<any> })
     if not node.children then return end
 
-    local cache = {}
-    for child in node.children do
-        table.insert(cache, child)
+    for child in next, node.children do
+        table.insert(update_queue, child)
+        rec(child, update_queue)
     end
 
-    for _, child in next, cache do
-        open_scope(child)
-        run_cleanups(child)
-        run_effect(child)
+    table.clear(node.children)
+end
+
+local function update<T>(node: StartNode<T>)
+    local update_queue = {} :: { Node<any> }
+    --assert(#update_queue == 0, "update already in progress")
+    rec(node, update_queue)
+
+    for _, n in next, update_queue do
+        open_scope(n) -- todo
+        run_cleanups(n)
+        run_effect(n)
         close_scope()
-        update(child)
-    end
     end
 
-local function track<T>(node: Node<T>)
-    add_child(node, get_scope())
+    table.clear(update_queue)
+end
+
+local function track<T>(node: StartNode<T>)
+    local scope = get_scope()
+    assert(scope)
+    if scope.effect then -- todo
+        add_child(node, scope)
+    end
 end
 
 local function create_node<T>(value: T): Node<T>
-    return {
+    local node: Node<T> = {
         cache = value,
-        effect = function() end,
-        cleanups = false,
-        children = false
+        effect = false,
+        cleanups = false :: false,
+        children = false :: false
     }
+
+    active[node] = true
+
+    return node
 end
 
-local function get_children(node: Node<unknown>): { Node<unknown> }
+local function get_children<T>(node: Node<T>): { Node<unknown> }
     if not node.children then return {} end
 
     local children = {}
@@ -151,7 +169,7 @@ local function get_children(node: Node<unknown>): { Node<unknown> }
         table.insert(children, child)
     end
 
-    return children
+    return children :: { Node<any> }
 end
 
 local function create_start_node<T>(value: T): StartNode<T>
@@ -159,10 +177,10 @@ local function create_start_node<T>(value: T): StartNode<T>
 end
 
 return table.freeze {
-    open_root_scope = open_root_scope,
     open_scope = open_scope,
     close_scope = close_scope,
     get_scope = get_scope,
+    get_stack_scope = get_stack_scope,
     add_cleanup = add_cleanup,
     destroy = destroy,
     run_cleanups = run_cleanups,

src/maps.luau

@@ -9,12 +9,8 @@ type Scope = graph.Scope
 type StartNode<T> = graph.StartNode<T>
 local create_node = graph.create_node
 local create_start_node = graph.create_start_node
-local create_scope = graph.create_scope
 local track = graph.track
 local update = graph.update
-local capture = graph.capture
-local capture_parents = graph.capture_parents
-local add_child = graph.add_child
 local get_scope = graph.get_scope
 local open_scope = graph.open_scope
 local close_scope = graph.close_scope
@@ -33,9 +29,8 @@ end
 
 -- todo: optimize output array
 local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI, K) -> VO): () -> { VO }
-    assert(get_scope())
-
-    local root = create_scope()
+    local owner = get_scope()
+    assert(owner)
 
     local input_cache = {} :: Map<K, VI>
     local output_cache = {} :: Map<K, VO>
@@ -65,7 +60,7 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
 
         table.clear(remove_queue)
 
-        open_scope(root)
+        open_scope(owner) -- todo: needed?
 
         -- process new or changed values
         for i, v in next, data do
@@ -73,10 +68,11 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
 
             if cv ~= v then
                 if cv == nil then
-                    local scope = create_scope()
+                    local scope = create_node(false)
                     scopes[i] = scope
 
                     open_scope(scope)
+                    track(owner)
 
                     local node = create_start_node(v)
                     input_nodes[i] = node
@@ -112,9 +108,11 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
         update_children(input())
     end
 
-    local value = capture_parents(output, input)
+    open_scope(output)
 
-    output.cache = update_children(value)
+    output.cache = update_children(input())
+
+    close_scope()
 
     return function()
         track(output)
@@ -124,9 +122,8 @@ end
 
 -- todo: optimize output array
 local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () -> K) -> VO): () -> { VO }
-    assert(get_scope())
-
-    local root = create_scope()
+    local owner = get_scope()
+    assert(owner)
     
     local cur_input_cache_up = {} :: Map<VI, K>
     local new_input_cache_up = {} :: Map<VI, K>
@@ -159,7 +156,7 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
             local cv = cur_input_cache[v]
             
             if cv == nil then
-                local scope = create_scope()
+                local scope = create_node(false)
                 scopes[v] = scope
 
                 open_scope(scope)
@@ -213,9 +210,11 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
         update_children(input())
     end
 
-    local value = capture_parents(output, input)
+    open_scope(output)
 
-    output.cache = update_children(value)
+    output.cache = update_children(input())
+
+    close_scope()
 
     return function()
         track(output)

src/root.luau

@@ -5,24 +5,24 @@ local throw = require(script.Parent.throw)
 local on_gc = require(script.Parent.on_gc)()
 local graph = require(script.Parent.graph)
 type Node<T> = graph.Node<T>
-local create_scope = graph.create_scope
+local create_node = graph.create_node
 local open_scope = graph.open_scope
 local close_scope = graph.close_scope
 local get_scope = graph.get_scope
 local destroy = graph.destroy
 
 local function root<T>(fn: () -> T): (T, () -> ())
-    assert(not get_scope())
-    local scope = create_scope()
+    --assert(not get_scope())
+    local node = create_node(false)
 
-    open_scope(scope)
+    open_scope(node)
 
     local v = fn()
 
     close_scope()
 
     return v, function()
-        destroy(scope)
+        destroy(node)
     end
 end
 

src/spring.luau

@@ -27,8 +27,10 @@ type Node<T> = graph.Node<T>
 type StartNode<T> = graph.StartNode<T>
 local create_node = graph.create_node
 local create_start_node = graph.create_start_node
+local get_scope = graph.get_scope
+local open_scope = graph.open_scope
+local close_scope = graph.close_scope
 local update = graph.update
-local capture = graph.capture
 local add_child = graph.add_child
 local track = graph.track
 
@@ -148,7 +150,18 @@ local springs: { [SpringData<any>]: StartNode<any> } = {}
 setmetatable(springs, { __mode = "v" })
 
 local function spring<T>(source: () -> T, period: number?, damping_ratio: number?): () -> T
-    local inputs, initial_value = capture(source)
+    local owner = get_scope()
+    assert(owner)
+
+    local updater = create_node(false)
+    updater.effect = true :: any -- todo
+
+    add_child(owner, updater)
+    open_scope(updater)
+
+    local initial_value = source()
+
+    close_scope()
 
     local vtype = typeof(initial_value)
     
@@ -181,7 +194,6 @@ local function spring<T>(source: () -> T, period: number?, damping_ratio: number
     
     local output = create_start_node(initial_value)
 
-    local updater = create_node(false)
     updater.effect = function()
         local v = source()
         data.x1_123, data.x1_456 = type_to_vec6[typeof(v)](v)
@@ -189,10 +201,6 @@ local function spring<T>(source: () -> T, period: number?, damping_ratio: number
         springs[data] = output -- todo: investigate why insertion is not O(1) at ~20k springs
     end
 
-    for _, input in next, inputs do
-        add_child(input, updater)
-    end
-
     return function()
         track(output)
         return output.cache
@@ -258,6 +266,7 @@ local function update_spring_sources()
         else
             output.cache = vec6_to_type[typeof(data.source_value)](x0_123, x0_456)
         end
+
         update(output)
     end
 

src/untrack.luau

@@ -1,20 +1,25 @@
 if not game then script = require "test/relative-string" end
 
+local create = require(script.Parent.create)
 local graph = require(script.Parent.graph)
 type Node<T> = graph.Node<T>
-local refs = graph.refs
+local create_node = graph.create_node
+local get_stack_scope = graph.get_stack_scope
+local open_scope = graph.open_scope
+local close_scope = graph.close_scope
+
+local non_tracking_scope = create_node(false)
 
 local function untrack<T>(source: () -> T): T
-    local initial = #refs
+    local scope = get_stack_scope(1)
 
-    local value = source()
+    open_scope(scope or non_tracking_scope)
 
-    -- remove any references made since `untrack()` was called
-    for i = initial, #refs do
-        refs[i] = nil
-    end
+    local v = source()
 
-    return value
+    close_scope()
+
+    return v
 end
 
 return untrack

src/watch.luau

@@ -2,20 +2,24 @@ if not game then script = require "test/relative-string" end
 
 local graph = require(script.Parent.graph)
 local create_node = graph.create_node
-local capture_parents = graph.capture_parents
 local get_scope = graph.get_scope
 local open_scope = graph.open_scope
 local close_scope = graph.close_scope
+local add_child = graph.add_child
+local track = graph.track
 
 local function watch(effect: () -> ())
-    assert(get_scope())
+    local owner = get_scope()
+    assert(owner)
 
     local node = create_node(false)
     node.effect = effect
 
-    open_scope(node.scope)
+    add_child(owner, node)
 
-    capture_parents(node, effect :: () -> any)
+    open_scope(node)
+
+    effect()
 
     close_scope()
 end

test/tests.luau

@@ -1,13 +1,15 @@
 local testkit = require("test/testkit")
 local TEST, CASE, CHECK, FINISH, SKIP = testkit.test()
 
-SKIP"graph"
-
 local mock = require "test/mock"
 local Instance, Signal = mock.Instance, mock.Signal
 local Vector2, UDim2 = mock.Vector2, mock.UDim2
 
 local vide = require "src/init"
+local graph = require "src/graph"
+type Node<T> = graph.Node<T>
+
+type Map<K, V> = { [K] : V }
 
 local function gc(n: number?)
     for i = 1, n or 3 do
@@ -27,26 +29,40 @@ local function wrap_root(fn: () -> ())
     end
 end
 
+local NIL = NIL
+
 TEST("graph", function()
-    local graph = require "src/graph"
     local create_node = graph.create_node
+    local create_start_node = graph.create_start_node
     local track = graph.track
     local update = graph.update
     local add_child = graph.add_child
-    local open_root_scope = graph.open_root_scope
+    local get_scope = graph.get_scope
     local open_scope = graph.open_scope
     local close_scope = graph.close_scope
     local get_children = graph.get_children
+    local add_cleanup = graph.add_cleanup
+    local destroy = graph.destroy
 
-    do CASE "node creation"
-        local node = create_node(1)
-        CHECK(node.cache == 1)
+    local function node<T>(v: T?)
+        local n = create_node(v or false)
+        n.effect = function() end
+        return n
+    end
+
+    local function scope()
+        return create_node(false)
+    end
+
+    local function cleanup(fn: () -> ())
+        local node = assert(get_scope())
+        add_cleanup(node, fn)
     end
 
     do CASE "link nodes"
-        local a = create_node(nil)
-        local b = create_node(nil)
-        local c = create_node(nil)
+        local a = node()
+        local b = node()
+        local c = node()
 
         open_scope(c)
 
@@ -60,9 +76,9 @@ TEST("graph", function()
     end
 
     do CASE "rerun linked nodes"
-        local a = create_node(nil)
-        local b = create_node(nil)
-        local c = create_node(nil)
+        local a = node()
+        local b = node()
+        local c = node()
 
         local count = 0
 
@@ -87,53 +103,166 @@ TEST("graph", function()
         CHECK(count == 3)
     end
 
-    do CASE "etst"
-        --[[
+    do CASE "case 1"
+        -- local function indexes<K, V>(input: Node<Map<K, V>>): Map<K, Node<V>>
+        --     local root = get_scope()
+        --     local updated = create_node(false)
 
-        root
-            Items -> Indexes()
+        --     local scopes = {}
+        --     local outputs = {}
 
-                indexes_root
-                    v1 + sel -> bind
-                    v2 + sel -> bind
+        --     function updated.effect()
+        --         open_scope(root)
 
-        ]]
-        local items = create_node { 1, 2 }
+        --         for i, v in input do
+        --             if not scopes[i] then
+        --                 scopes[i] = create_node(false)
+        --                 outputs[i] = create_start_node(v)
+        --             end
         
-        local count = 0
+        --             open_scope(scopes[i])
+        --             outputs[i].cache = v
+        --             update(outputs[i])
+        --             close_scope()
+        --         end
 
-        local function effect()
-            track(a)
-            track(b)
-            count += 1
+        --         for i, v in outputs do
+        --             if input[i] == nil then
+        --                 destroy(scopes[i])
+        --             end
+        --         end
+
+        --         close_scope()
+        --     end
+
+        --     open_scope(updated)
+        --     updated.effect(false)
+        --     close_scope()
+            
+        --     return outputs
+        -- end
+
+        -- construct graph
+
+        local items = node { "a", "b" }
+        local selected = node "a"
+
+        local root = scope()
+
+        local scope1 = scope()
+        local scope2 = scope()
+
+        local items_updated
+
+        local bind1
+        local bind2
+
+        local cleaned = {} :: { [any]: any }
+
+        local function clean(s)
+            cleanup(function()
+                cleaned[s] = true
+            end)
         end
 
-        c.effect = effect
+        do open_scope(root) 
+            clean "root"
+            items_updated = node()
+            items_updated.effect = function() end
+            track(items_updated) -- should not
 
-        open_scope(c)
+            add_child(root, items_updated)
+            do open_scope(items_updated)
+                track(items)
 
-        effect()
+                do open_scope(root)
+                    add_child(root, scope1)
+                    do open_scope(scope1)
+                        clean "scope1"
+                        bind1 = node()
+                        bind1.effect = function() end
 
-        close_scope()
+                        add_child(scope1, bind1)
+                        do open_scope(bind1)
+                            clean "bind1"
+                            track(selected)
+                        close_scope() end
+                    close_scope() end
 
-        CHECK(count == 1)
-        update(a)
-        CHECK(count == 2)
-        update(b)
-        CHECK(count == 3)
+                    add_child(root, scope2)
+                    do open_scope(scope2)
+                        clean "scope2"
+                        bind2 = node()
+                        bind2.effect = function() end
+                        add_child(scope2, bind2)
+                        do open_scope(bind2)
+                            clean "bind2"
+                            track(selected)
+                        close_scope() end
+                    close_scope() end
+                close_scope() end
+            close_scope() end 
+        close_scope() end
+        
+
+        -- verify graph
+
+        do
+            local c = get_children(items_updated)
+            CHECK(#c == 0)
+        end
+    
+        do
+            local c = get_children(root)
+            CHECK(#c == 3)
+            CHECK(table.find(c, items_updated))
+            CHECK(table.find(c, scope1 :: Node<any>))
+            CHECK(table.find(c, scope2 :: Node<any>))
+        end
+
+        do
+            local c = get_children(selected)
+            CHECK(#c == 2)
+            CHECK(table.find(c, bind1))
+            CHECK(table.find(c, bind2))
+        end
+
+        do
+            local c = get_children(scope1)
+            CHECK(#c == 1)
+            CHECK(table.find(c, bind1))
+        end
+
+        do
+            local c = get_children(scope2)
+            CHECK(#c == 1)
+            CHECK(table.find(c, bind2))
+        end
+
+        -- destroy
+
+        CHECK(table.find(get_children(root), scope1 :: Node<any>))
+
+        destroy(scope1)
+        CHECK(table.find(get_children(root), scope1 :: Node<any>))
+        CHECK(cleaned.scope1)
+        CHECK(cleaned.bind1)
+        scope1 = NIL
+        bind1 = NIL
+        bind2 = NIL
+        gc()
+        CHECK(#get_children(root) == 2)
+        CHECK(#get_children(selected) == 1)
     end
 
     -- todo: further tests
 
     do CASE "nodes garbage collection"
         local wref = weak { create_node(1) }
+        destroy(wref[1])
         gc()
         CHECK(not wref[1])
     end
-
-    do CASE "test"
-        local x = 1
-    end
 end)
 
 TEST("source()", wrap_root(function()
@@ -154,31 +283,31 @@ TEST("source()", wrap_root(function()
     do CASE "does not update if same value"
         local src = source(1)
 
-        local count = -1
+        local count = 0
         watch(function()
             src()
             count += 1
         end)
 
-        CHECK(count == 0)
-        src(1)
-        CHECK(count == 0)
-        src(2)
         CHECK(count == 1)
+        src(1)
+        CHECK(count == 1)
+        src(2)
+        CHECK(count == 2)
     end
 
     do CASE "does update if same value is mutable table"
         local src = source {}
 
-        local count = -1
+        local count = 0
         watch(function()
             src()
             count += 1
         end)
 
-        CHECK(count == 0)
-        src(src())
         CHECK(count == 1)
+        src(src())
+        CHECK(count == 2)
     end
 
     do CASE "does not update if same value is frozen table"
@@ -187,25 +316,26 @@ TEST("source()", wrap_root(function()
 
         local src = source(a)
 
-        local count = -1
+        local count = 0
         watch(function()
             src()
             count += 1
         end)
 
-        CHECK(count == 0)
+        CHECK(count == 1)
         src(a)
-        CHECK(count == 0)
-        src(b)
         CHECK(count == 1)
         src(b)
-        CHECK(count == 1)
+        CHECK(count == 2)
+        src(b)
+        CHECK(count == 2)
     end
 end))
 
 TEST("derive()", wrap_root(function()
     local source = vide.source
     local derive = vide.derive
+    local watch = vide.watch
 
     do CASE "derive new value on source change"
         local a = source(1)
@@ -236,6 +366,30 @@ TEST("derive()", wrap_root(function()
         CHECK(c() == 2)
     end
 
+    do CASE "does not update if same value"
+        local num = source(0)
+
+        local is_even = derive(function()
+            return num() % 2 == 0
+        end)
+
+        local count = 0
+
+        watch(function()
+            is_even()
+            count += 1
+        end)
+        
+        num(1) -- odd
+        CHECK(count == 2)
+        num(2) -- even
+        CHECK(count == 3)
+        num(4) -- even
+        CHECK(count == 3)
+        num(5) -- odd
+        CHECK(count == 4)
+    end
+
     do CASE "garbage collection"
         -- check that `b` does not allow gc of `a`        
         local a = source(1)
@@ -244,7 +398,7 @@ TEST("derive()", wrap_root(function()
             return a()
         end)
 
-        b = nil :: any
+        b = NIL
 
         local wref = weak { a }
 
@@ -256,9 +410,8 @@ end))
 TEST("watch()", wrap_root(function()
     local source = vide.source
     local watch = vide.watch
-    local cleanup = vide.cleanup
 
-    do CASE "capture sources"
+    do CASE "rerun on source change"
         local a = source(1)
         local b = source(1)
 
@@ -275,70 +428,31 @@ TEST("watch()", wrap_root(function()
         b(2)
         CHECK(count == 3)
     end
-
-    do CASE "side-effect cleanup"
-        local state = source(1)
-
-        local effect_count = 0
-        local cleanup_count = 0
-
-        watch(function()
-            state()
-            effect_count += 1
-            cleanup(function() cleanup_count += 1 end)
-        end)
-
-        CHECK(effect_count == 1)
-        CHECK(cleanup_count == 0)
-        state(2)
-        CHECK(effect_count == 2)
-        CHECK(cleanup_count == 1)
-    end
-
-    do CASE "garbage collection"
-        local function factory(p)
-            return function()
-                p()
-            end
-        end
-
-        do -- state prevents gc of watcher
-            local state = source(1)
-
-            local wref
-
-            do
-                local effect = factory(state)
-                watch(effect)
-                wref = { effect }
-            end
-
-            gc()
-            CHECK(wref[1])
-        end
-
-        do -- state can gc with watcher
-            local wref
-
-            do
-                local state = source(1)
-                local effect = factory(state)
-                watch(effect)
-                wref = weak { state }
-            end
-
-            gc()
-            CHECK(not wref[1])
-        end
-    end
 end))
 
 TEST("cleanup()", wrap_root(function()
+    local root = vide.root
     local source = vide.source
     local watch = vide.watch
     local cleanup = vide.cleanup
 
-    do CASE "cleanup runs for watcher"
+    do CASE "root cleanup"
+        local count = 0
+
+        local _, destroy = root(function()
+            cleanup(function()
+                count += 1
+            end)
+
+            return nil
+        end)
+
+        CHECK(count == 0)
+        destroy()
+        CHECK(count == 1)
+    end
+
+    do CASE "cleanup on rerun"
         local state = source(1)
 
         local watched = 0
@@ -381,8 +495,10 @@ TEST("cleanup()", wrap_root(function()
 end))
 
 TEST("create()", wrap_root(function()
+    local root = vide.root
     local create = vide.create
     local source = vide.source
+    local cleanup = vide.cleanup
 
     do CASE "apply default properties"
         local defaults = require("src/defaults")
@@ -429,9 +545,7 @@ TEST("create()", wrap_root(function()
             {
                 Text = "1",
 
-                {
-                    Text = "2"
-                }
+                { Text = "2" }
             }
         }
 
@@ -489,129 +603,38 @@ TEST("create()", wrap_root(function()
         CHECK(label.Text == "Bar")
     end
 
-    do CASE "binding garbage collection"
-        --[[
-        do -- instance should gc when unparented
-            local state = source("Hi")
+    do CASE "binding destroy"
+        local count = 0
 
-            local wref = weak {
-                create "TextLabel" {
-                    Text = state,
-                }
-            }
+        local _, destroy = root(function()
+            local src = source(0)
 
-            gc()
-            CHECK(not wref[1])
+            return create "TextLabel" {
+                Text = function()
+                    cleanup(function()
+                        count += 1
+                    end)
+
+                    return src()
                 end
-        ]]
-
-        --[[
-        do -- instance should not gc when parented
-            local state = source("Hi")
-
-            local parent = create "Frame" {}
-
-            local wref = weak {
-                create "TextLabel" {
-                    Parent = parent,
-                    Text = state,
-                }
             }
+        end)
 
-            gc()
-            CHECK(wref[1])
-
-            wref[1].Parent = nil
-            wref[1].Parent = parent
-
-            gc()
-            CHECK(wref[1])
-
-            wref[1]:Destroy()
-
-            gc()
-            CHECK(not wref[1])
-        end
-        ]]
-        
-        --[[
-        do -- instance does not allow gc of state
-            local label
-            local wref
-
-            do
-                local state = source("Hi")
-                label = create "TextLabel" {
-                    Name = state,
-                }
-                wref = weak { state :: any, label }
-
-            end
-
-            gc()
-            CHECK(wref[2])
-            CHECK(wref[1])
-        end
-        ]]
-        
-        do -- state and instance should gc once both exit scope
-            local wref
-    
-            do
-                local text = source("Hi")
-
-                local box = create "TextLabel" {
-                    Text = text,
-                }
-
-                wref = weak { text = text, box = box}
-            end
-
-            gc()
-            CHECK(not wref.text)
-            CHECK(not wref.box)
-        end
-        
-        --[[
-        do -- binding should gc despite state still existing after instance is gc
-            local state = source("Hi")
-
-            local node = require "src/graph".capture(state)[1]
-
-            local wref
-
-            do
-                local instance = create "TextLabel" {
-                    Text = state,
-                }
-
-                local binding = assert(node[1])
-
-                wref = weak {
-                    instance = instance,
-                    binding = binding
-                }
-            end
-            
-            CHECK(wref.binding)
-
-            gc()
-            CHECK(not wref.instance)
-            CHECK(not wref.binding)
-        end
-        ]]
+        CHECK(count == 0)
+        destroy()
+        CHECK(count == 1)
     end
 
     do CASE "bind same state to multiple instance properties"
-        local state = source "1"
+        local src = source "1"
 
         local text = create "TextBox" {
-            Name = state,
-            Text = state,
-            PlaceholderText = state
+            Name = src,
+            Text = src,
+            PlaceholderText = src
         }
 
-        state "2"
+        src "2"
 
         CHECK(text.Name == "2")
         CHECK(text.Text == "2")
@@ -619,7 +642,7 @@ TEST("create()", wrap_root(function()
     end
 
     do CASE "bind children"
-        local state = source()
+        local children = source()
 
         local a, b, c = 
             create "TextLabel" { Name = "A" },
@@ -627,29 +650,29 @@ TEST("create()", wrap_root(function()
             create "TextLabel" { Name = "C" }
 
         local frame = create "Frame" {
-            state
+            children
         }
   
-        state { a, b }
+        children { a, b }
 
         CHECK(frame:FindFirstChild "A")
         CHECK(frame:FindFirstChild "B")
 
         -- check that b is removed and c is added while a remains untouched
         
-        state { a, c }
+        children { a, c }
 
         CHECK(frame:FindFirstChild "A")
         CHECK(frame:FindFirstChild "C")
         CHECK(not frame:FindFirstChild "B")
 
-        state(nil)
+        children(nil)
 
         CHECK(#frame:GetChildren() == 0)
     end
 
-    --[[
-    do CASE "Parent set to nil by state does not allow gc"
+    do CASE "parent bound to source"
+        local wref, destroy = root(function()
             local frame = create "Frame" { Name = "Parent" }
             local parent = source(frame :: Frame?)
 
@@ -662,15 +685,18 @@ TEST("create()", wrap_root(function()
 
             parent(nil)
 
+            return wref
+        end)
+
         gc()
         CHECK(wref[1])
 
-        wref[1]:Destroy()
+        destroy()
+        destroy = NIL
 
         gc()
         CHECK(not wref[1])
     end
-    ]]
 
     do CASE "garbage collection test"
         local wref
@@ -761,7 +787,7 @@ TEST("indexes()", wrap_root(function()
 
         CHECK(t[1].Text == "1")
         CHECK(t[2].Text == "2")
-        CHECK(t[3] == nil :: any)
+        CHECK(t[3] == NIL)
         CHECK(destroyed == true)
     end
 
@@ -775,7 +801,7 @@ TEST("indexes()", wrap_root(function()
 
             local wref = weak { input }
 
-            input = nil :: any
+            input = NIL
 
             gc()
             CHECK(wref[1]) 
@@ -790,7 +816,7 @@ TEST("indexes()", wrap_root(function()
 
             local wref = weak { output }
 
-            output = nil :: any
+            output = NIL
 
             gc()
             CHECK(not wref[1])
@@ -880,7 +906,7 @@ TEST("values()", wrap_root(function()
 
         CHECK(t[1].Text == "1")
         CHECK(t[2].Text == "2")
-        CHECK(t[3] == nil :: any)
+        CHECK(t[3] == NIL)
         CHECK(destroyed == true)
     end
 
@@ -931,13 +957,14 @@ TEST("spring()", wrap_root(function()
 
     do CASE "update source (on next step)"
         local value = source(10)
-        local springed = spring(value, 1, 1)
+        local sprung = spring(value, 1, 1)
 
+        CHECK(sprung() == 10)
         value(20)
-        CHECK(springed() == 10)
+        CHECK(sprung() == 10)
         vide.step(1/60)
-        CHECK(springed() ~= 10)
-        CHECK(springed() > 10)
+        CHECK(sprung() ~= 10)
+        CHECK(sprung() > 10)
     end
 
     do CASE "garbage collection"
@@ -947,7 +974,7 @@ TEST("spring()", wrap_root(function()
             local _output = spring(input)
 
             local wref = weak { input }
-            input = nil :: any
+            input = NIL
 
             gc()
             CHECK(wref[1])
@@ -959,28 +986,26 @@ TEST("spring()", wrap_root(function()
             local output = spring(input)
         
             local wref = weak { output }
-            output = nil :: any
+            output = NIL
             
             gc()
             CHECK(not wref[1])
         end
 
-        do -- spring data gc
-            local capture = require "src/graph".capture
+        -- do -- spring data gc
+        --     local input = source(10)
 
-            local input = source(10)
+        --     local wref do
+        --         local output, data = (spring :: any)(input)
+        --         input(input() + 1) -- schedule spring calculation
+        --         local output_node = unpack(capture(output))
+        --         wref = weak { output_node, data }
+        --     end
     
-            local wref do
-                local output, data = (spring :: any)(input)
-                input(input() + 1) -- schedule spring calculation
-                local output_node = unpack(capture(output))
-                wref = weak { output_node, data }
-            end
-    
-            gc()
-            CHECK(not wref[1])
-            CHECK(not wref[2])
-        end
+        --     gc()
+        --     CHECK(not wref[1])
+        --     CHECK(not wref[2])
+        -- end
     end
 
     do CASE "garbage collection (binded)"
@@ -992,7 +1017,7 @@ TEST("spring()", wrap_root(function()
         }
 
         local wref = { output }
-        output = nil :: any
+        output = NIL
 
         gc()
         CHECK(wref[1]) -- `output` should not gc
@@ -1026,8 +1051,11 @@ TEST("spring()", wrap_root(function()
 end))
 
 TEST("untrack()", wrap_root(function()
+    local root = vide.root
     local source = vide.source
+    local derive = vide.derive
     local watch = vide.watch
+    local cleanup = vide.cleanup
     local untrack = vide.untrack
 
     do CASE "does not register dependency"
@@ -1075,6 +1103,55 @@ TEST("untrack()", wrap_root(function()
         b(1)
         CHECK(count == 1)
     end
+
+    do CASE "outer scope"
+        local outer_count = 0
+        local inner_count = 0
+        local cleaned_count = 0
+
+        local input = source(0)
+
+        local output, destroy = root(function()
+            local output = derive(function()
+                outer_count += 1
+
+                return untrack(function()
+                    return derive(function()
+                        inner_count += 1
+    
+                        cleanup(function()
+                            cleaned_count += 1
+                        end)
+    
+                        return tostring(input())
+                    end)
+                end)
+            end)
+
+            return output
+        end)
+
+        CHECK(outer_count == 1)
+        CHECK(inner_count == 1)
+        CHECK(cleaned_count == 0)
+
+        local output2 = output()
+
+        CHECK(output2() == "0")
+
+        input(1)
+
+        -- todo
+        CHECK(outer_count == 2)
+        CHECK(inner_count == 3)
+        CHECK(cleaned_count == 1)
+
+        local output3 = output()
+        CHECK(output2() == "1")
+        CHECK(output3() == "1")
+
+        CHECK(output2 ~= output3)
+    end
 end))
 
 TEST("events", function()