Add repeated read test

src/graph.luau

@@ -181,44 +181,6 @@ local function evaluate_node<T>(node: Node<T>)
     return cur_value ~= new_value -- node has changed value
 end
 
--- local function update_from<T>(node: StartNode<T>, n0: number)
---     if not node[1] then return end
-
---     local n = n0
-
---     -- unparent all children and queue for eval
---     do
---         local child = node[1]
---         while child do
---             --assert(child.parents.owner)
---             unparent(child)
---             n += 1
---             update_queue[n] = child
---             child = node[1]
---         end
---     end
-
---     update_queue.n = n
-
---     -- evaluate all queued children
---     for i = n0 + 1, n do
---         local child = update_queue[i]
---         assert(type(child.effect) == "function")
-
---         if evaluate_node(child) then
---             update_from(child, n)
---         end
-
---         update_queue[i] = false :: any -- false instead of nil to avoid sparse
---     end
-
---     update_queue.n = n0
--- end
-
--- local function update<T>(node: StartNode<T>)
---     update_from(node, update_queue.n)
--- end
-
 local function queue_children<T>(node: StartNode<T>)
     local i = update_queue.n
     local child = node[1]

test/tests.luau

@@ -1969,7 +1969,6 @@ TEST("graph edge cases", wrap_root(function()
 
         a(1)
 
-        print(e())
         CHECK(count.b == 2)
         CHECK(count.c == 2)
         CHECK(count.d == 2)
@@ -1985,7 +1984,15 @@ TEST("graph edge cases", wrap_root(function()
     end
 
     do CASE "repeated read"
+        local a = source(0)
+        local b = derive(function() return a() + a() end)
 
+        local count = 0
+        effect(function() b(); count += 1 end)
+
+        a(1)
+        CHECK(b() == 2)
+        CHECK(count == 2)
     end
 end))