[FIX] concurrency issue (more robust handling of children per render)

Before this commit, the list of all children was managed at the level of
the root fiber, but this could cause issue when subfibers would be
reused. With this commit, we use the childrenMap object that exists on
each fiber instead.

src/app/app.ts

@@ -67,7 +67,7 @@ export class App<
   }
 
   makeNode(Component: ComponentConstructor, props: any): ComponentNode {
-    return new ComponentNode(Component, props, this);
+    return new ComponentNode(Component, props, this, null, null);
   }
 
   mountNode(node: ComponentNode, target: HTMLElement, options?: MountOptions) {

src/component/component_node.ts

@@ -109,13 +109,11 @@ export function component<P extends object>(
         throw new Error(`Cannot find the definition of component "${name}"`);
       }
     }
-    node = new ComponentNode(C, props, ctx.app, ctx);
+    node = new ComponentNode(C, props, ctx.app, ctx, key);
     ctx.children[key] = node;
     node.initiateRender(new Fiber(node, parentFiber));
   }
   parentFiber.childrenMap[key] = node;
-
-  parentFiber.root!.reachedChildren.add(node);
   return node;
 }
 
@@ -133,6 +131,7 @@ export class ComponentNode<P extends object = any, E = any> implements VNode<Com
   bdom: BDom | null = null;
   status: STATUS = STATUS.NEW;
   forceNextRender: boolean = false;
+  parentKey: string | null;
 
   renderFn: Function;
   parent: ComponentNode | null;
@@ -149,10 +148,17 @@ export class ComponentNode<P extends object = any, E = any> implements VNode<Com
   patched: LifecycleHook[] = [];
   willDestroy: LifecycleHook[] = [];
 
-  constructor(C: ComponentConstructor<P, E>, props: P, app: App, parent?: ComponentNode) {
+  constructor(
+    C: ComponentConstructor<P, E>,
+    props: P,
+    app: App,
+    parent: ComponentNode | null,
+    parentKey: string | null
+  ) {
     currentNode = this;
     this.app = app;
-    this.parent = parent || null;
+    this.parent = parent;
+    this.parentKey = parentKey;
     this.level = parent ? parent.level + 1 : 0;
     applyDefaultProps(props, C);
     const env = (parent && parent.childEnv) || app.env;

src/component/fibers.ts

@@ -25,9 +25,6 @@ export function makeRootFiber(node: ComponentNode): Fiber {
     current.children = [];
     current.childrenMap = {};
     current.bdom = null;
-    if (current === root) {
-      root.reachedChildren = new WeakSet();
-    }
     if (fibersInError.has(current)) {
       fibersInError.delete(current);
       fibersInError.delete(root);
@@ -108,7 +105,7 @@ export class Fiber {
           scheduler.delayedRenders.push(this);
           return;
         } else {
-          if (!root.reachedChildren.has(prev)) {
+          if (!(prev.parentKey! in current.fiber.childrenMap)) {
             // is dead. but we keep the render around just in case
             scheduler.delayedRenders.push(this);
             return;
@@ -150,8 +147,6 @@ export class RootFiber extends Fiber {
   // i.e.: render triggered in onWillUnmount or in willPatch will be delayed
   locked: boolean = false;
 
-  reachedChildren: WeakSet<ComponentNode> = new WeakSet();
-
   complete() {
     const node = this.node;
     this.locked = true;