src/effect.luau

@@ -14,6 +14,7 @@ local function effect<T>(effect: (T) -> T, initial_value: T)
     end; assert(owner)
 
     local node = create_node(initial_value, effect)
+
     set_owner(node, owner)
     evaluate_node(node)
 end

src/graph.luau

@@ -11,11 +11,8 @@ export type StartNode<T> = {
 export type Node<T> =  {
     cache: T,
     effect:  ((T) -> T) | false,
-
-    owner: Node<T> | false,
     cleanups: { () -> () } | false,
-    
-    parents: { StartNode<T> },
+    parents: { owner: StartNode<T>?, [number]: StartNode<T> },
     [number]: Node<T>
 }
 
@@ -57,7 +54,7 @@ local function add_child<T>(parent: StartNode<any>, child: Node<any>)
 end
 
 local function set_owner(node: Node<any>, owner: Node<any>)
-    node.owner = owner
+    node.parents.owner = owner
     table.insert(owner, node)
 end
 
@@ -100,20 +97,21 @@ local function remove_child<T>(parent: StartNode<T>, child: Node<T>)
 end
 
 local function unparent<T>(node: Node<T>)
-    for _, parent in node.parents do
-        remove_child(parent, node)
-    end
+    local parents = node.parents
 
-    table.clear(node.parents)
+    for i, parent in ipairs(parents) do
+        remove_child(parent, node)
+        parents[i] = nil
+    end
 end
 
 local function destroy<T>(node: Node<T>)
     run_cleanups(node)
     unparent(node)
 
-    if node.owner then
-        remove_child(node.owner, node)
-        node.owner = false
+    if node.parents.owner then
+        remove_child(node.parents.owner, node)
+        node.parents.owner = nil
     end
 
     while node[1] do destroy(node[1]) end
@@ -188,11 +186,9 @@ end
 local function create_node<T>(value: T, effect: false | (T) -> T): Node<T>
     local node: Node<T> = {
         cache = value,
-        owner = false,
         effect = effect,
         cleanups = false :: false,
         parents = {},
-        children = false :: false
     }
 
     return node
@@ -203,7 +199,7 @@ local function get_children<T>(node: Node<T>): { Node<unknown> }
 end
 
 local function create_start_node<T>(value: T): StartNode<T>
-    return { cache = value, children = false }
+    return { cache = value }
 end
 
 return table.freeze {

src/init.luau

@@ -14,7 +14,7 @@ local effect = require(script.effect)
 local cleanup = require(script.cleanup)
 local untrack = require(script.untrack)
 local derive = require(script.derive)
-local match = require(script.match)
+local switch = require(script.switch)
 local indexes, values = require(script.maps)()
 local spring, update_springs = require(script.spring)()
 local action = require(script.action)()
@@ -50,7 +50,7 @@ local vide = {
     source = source,
     effect = effect,
     derive = derive,
-    match = match,
+    switch = switch,
     indexes = indexes,
     values = values,
 

src/maps.luau

@@ -29,9 +29,6 @@ local function check_primitives(t: {})
     end
 end
 
--- todo: verify destruction of subscopes when owner scope is destroyed
-
--- todo: optimize output array
 local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI, K) -> VO): () -> { VO }
     local owner = get_scope()
     if not owner then
@@ -78,18 +75,23 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
                     local scope = create_node(false, false)
                     scopes[i] = scope :: Node<any>
 
+                    local node = create_start_node(v)
+
                     set_owner(scope, subowner)
                     open_scope(scope)
 
-                    local node = create_start_node(v)
-                    input_nodes[i] = node
-                    input_cache[i] = v
-                    output_cache[i] = transform(function()
+                    local ok, result = pcall(transform, function()
                         track(node)
                         return node.cache
                     end, i)
                     
                     close_scope()
+
+                    if not ok then error(result, 0) end
+                    
+                    input_nodes[i] = node
+                    input_cache[i] = v
+                    output_cache[i] = result
                 else
                     input_nodes[i].cache = v
                     update(input_nodes[i])
@@ -98,6 +100,7 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
             end
         end
 
+        -- todo: handle early error
         close_scope()
 
         local output_array = table.create(#scopes)
@@ -109,16 +112,16 @@ local function indexes<K, VI, VO>(input: () -> Map<K, VI>, transform: (() -> VI,
         return output_array
     end
 
-    local output = create_node(false :: any, function()
+    local node = create_node(false :: any, function()
         return update_children(input())
     end)
 
-    evaluate_node(output)
+    evaluate_node(node)
 
 
     return function()
-        track(output)
-        return output.cache
+        track(node)
+        return node.cache
     end
 end
 
@@ -162,17 +165,22 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
                 local scope = create_node(false, false)
                 scopes[v] = scope :: Node<any>
 
+                local node = create_start_node(i)
+    
                 set_owner(scope, subowner)
                 open_scope(scope)
                 
-                local node = create_start_node(i)
-                input_nodes[v] = node
-                output_cache[v] = transform(v, function()
+                local ok, result = pcall(transform, v, function()
                     track(node)
                     return node.cache
                 end)
                 
                 close_scope()
+
+                if not ok then error(result, 0) end
+
+                input_nodes[v] = node
+                output_cache[v] = result
             else
                 if cv ~= i then
                     input_nodes[v].cache = i
@@ -182,6 +190,7 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
             end
         end
 
+        -- todo: handle early error
         close_scope()
 
         -- remove old values
@@ -206,15 +215,15 @@ local function values<K, VI, VO>(input: () -> Map<K, VI>, transform: (VI, () ->
         return output_array
     end
 
-    local output = create_node(false :: any, function()
+    local node = create_node(false :: any, function()
         return update_children(input())
     end)
 
-    evaluate_node(output)
+    evaluate_node(node)
 
     return function()
-        track(output)
-        return output.cache
+        track(node)
+        return node.cache
     end
 end
 

src/match.luau

@@ -1,39 +0,0 @@
-if not game then script = require "test/relative-string" end
-
-local throw = require(script.Parent.throw)
-local flags = require(script.Parent.flags)
-local graph = require(script.Parent.graph)
-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 set_owner = graph.set_owner
-local track = graph.track
-local update = graph.update
-local get_scope = graph.get_scope
-local open_scope = graph.open_scope
-local close_scope = graph.close_scope
-local destroy = graph.destroy
-
-type Map<K, V> = { [K]: V }
-
-local function match<T, U>(source: () -> T, map: Map<T, () -> U?>): () -> U?
-    local owner = get_scope()
-    assert(owner)
-
-    local match_updater = create_node(nil :: U?)
-    function match_updater.effect()
-        local value = source()
-        open_scope(owner)
-        local component = map[value]()
-        close_scope()
-        return component
-    end
-
-    return function()
-        track(match_updater)
-        return match_updater.cache
-    end
-end
-
-return match

src/switch.luau

@@ -0,0 +1,66 @@
+if not game then script = require "test/relative-string" end
+
+local throw = require(script.Parent.throw)
+local graph = require(script.Parent.graph)
+type Node<T> = graph.Node<T>
+type StartNode<T> = graph.StartNode<T>
+local create_node = graph.create_node
+local evaluate_node = graph.evaluate_node
+local set_owner = graph.set_owner
+local track = graph.track
+local destroy = graph.destroy
+local get_scope = graph.get_scope
+local open_scope = graph.open_scope
+local close_scope = graph.close_scope
+
+type Map<K, V> = { [K]: V }
+
+local function switch<T, U>(source: () -> T): (map: Map<T, ((() -> U)?)>) -> () -> U?
+    return function(map)
+        local owner = get_scope()
+        if not owner then
+            throw("cannot switch in non-reactive scope")
+        end; assert(owner)
+
+        local scope: Node<false>?
+        local last_component: (() -> U)?
+
+        local function update(): U?
+            local component = map[source()]
+            if component == last_component then return nil end
+            last_component = component
+
+            if scope then
+                destroy(scope :: Node<any>)
+            end
+
+            if component == nil then return nil end
+
+            local new_scope = create_node(false, false)
+            scope = new_scope :: Node<any>
+            
+            set_owner(new_scope, owner)
+            open_scope(new_scope)
+        
+            local ok, result = pcall(component)
+
+            close_scope()
+
+            if not ok then error(result, 0) end
+
+            return result
+        end
+
+        local node = create_node(nil, update :: () -> any)
+
+        set_owner(node, owner)
+        evaluate_node(node)
+
+        return function()
+            track(node)
+            return node.cache
+        end
+    end
+end
+
+return switch

test/benchmark.luau

@@ -68,7 +68,6 @@ BENCH("derive 4 sources", function()
     end)
 end)
 
--- todo: why is this so fast?
 BENCH("set derived value", function()
     local src = vide.source(1)
 
@@ -110,7 +109,7 @@ BENCH("apply 8 properties", function()
     end
 end)
 
-BENCH("bind source", function()
+BENCH("bind property", function()
     local apply = require "src/apply"
 
     local instance = vide.create("Frame") {}

test/tests.luau

@@ -453,22 +453,6 @@ TEST("derive()", wrap_root(function()
         gc()
         CHECK(wref[1])
     end
-
-    do CASE "raw derive"
-        local a = source(1)
-        local b = derive(a)
-
-        local count = 0
-    
-        effect(function()
-            b()
-            count += 1
-        end)
-
-        CHECK(count == 1)
-        a(2)
-        CHECK(count == 2)
-    end
 end))
 
 TEST("effect()", wrap_root(function()
@@ -822,6 +806,72 @@ TEST("create()", wrap_root(function()
     end
 end))
 
+TEST("switch()", wrap_root(function()
+    local create = vide.create
+    local source = vide.source
+    local switch = vide.switch
+    local effect = vide.effect
+    local derive = vide.derive
+    local cleanup = vide.cleanup
+
+    do CASE "update on source change"
+        local input = source(true)
+
+        local output = switch(input) {
+            [true] = function() return 1 end,
+            [false] = function() return 0 end
+        }
+
+        local count = 0
+
+        effect(function() output(); count += 1 end)
+
+        CHECK(count == 1)
+        CHECK(output() == 1)
+        input(false)
+        CHECK(output() == 0)
+        CHECK(count == 2)
+        input(false)
+        CHECK(count == 2)
+        input(nil)
+        CHECK(output() == nil)
+    end
+
+    do CASE "scoped switch"
+        local input = source(true)
+
+        local owner_count = 0
+        local switch0_count = 0
+        local switch1_count = 0
+
+        cleanup(function() owner_count += 1 end)
+
+        local output = switch(input) {
+            [true] = function() 
+                cleanup(function() switch1_count += 1 end)
+                return 1
+            end,
+
+            [false] = function() 
+                cleanup(function() switch0_count += 1 end)
+                return 0
+            end
+        }
+
+        CHECK(output() == 1)
+        input(false)
+        CHECK(switch1_count == 1)
+        CHECK(switch0_count == 0)
+        input(true)
+        CHECK(switch1_count == 1)
+        CHECK(switch0_count == 1)
+        input(nil)
+        CHECK(switch1_count == 2)
+        CHECK(switch0_count == 1)
+        CHECK(owner_count == 0)
+    end
+end))
+
 TEST("indexes()", wrap_root(function()
     local create = vide.create
     local source = vide.source