Implement batched updates

No docs yet, more testing needed.

src/batch.luau

@@ -0,0 +1,23 @@
+if not game then script = require "test/relative-string" end
+
+local flags = require(script.Parent.flags)
+local throw = require(script.Parent.throw)
+local graph = require(script.Parent.graph)
+
+local function batch(setter: () -> ())
+    local already_batching = flags.batch
+
+    flags.batch = true
+
+    local ok, err: string? = pcall(setter)
+
+    flags.batch = false
+    
+    if not ok then throw(`error occured while batching updates: {err}`) end
+
+    if not already_batching then -- todo: flush anyways?
+        graph.flush_update_queue()
+    end
+end
+
+return batch

src/flags.luau

@@ -4,4 +4,4 @@ end
 
 local is_O2 = inline_test() ~= "inline_test"
 
-return { strict = not is_O2 }
+return { strict = not is_O2, batch = false }

src/graph.luau

@@ -193,10 +193,32 @@ local function queue_children<T>(node: StartNode<T>)
     update_queue.n = i
 end
 
+local function flush_update_queue()
+    -- todo: test with recursive batch sets
+    local n0 = 0
+
+    local i = n0 + 1
+    while i <= update_queue.n do
+        local node = update_queue[i]
+        --assert(node.effect)
+
+        if evaluate_node(node) then
+            queue_children(node)
+        end
+
+        update_queue[i] = false :: any
+        i += 1
+    end
+
+    update_queue.n = n0
+end
+
 local function update<T>(root: StartNode<T>)
     local n0 = update_queue.n
     queue_children(root)
 
+    if flags.batch then return end
+
     local i = n0 + 1
     while i <= update_queue.n do
         local node = update_queue[i]
@@ -257,5 +279,6 @@ return table.freeze {
     create_node = create_node,
     create_start_node = create_start_node,
     get_children = get_children,
+    flush_update_queue = flush_update_queue,
     scopes = scopes
 }

src/init.luau

@@ -11,9 +11,10 @@ local create = require(script.create)
 local apply = require(script.apply)
 local source = require(script.source)
 local effect = require(script.effect)
+local derive = require(script.derive)
 local cleanup = require(script.cleanup)
 local untrack = require(script.untrack)
-local derive = require(script.derive)
+local batch = require(script.batch)
 local switch = require(script.switch)
 local show = require(script.show)
 local indexes, values = require(script.maps)()
@@ -59,6 +60,7 @@ local vide = {
     -- util
     cleanup = cleanup,
     untrack = untrack,
+    batch = batch,
     read = function<T>(value: T | () -> T): T
         return if type(value) == "function" then value() else value
     end,