[IMP] big change: shallow render

With this commit, component only render child
components if they have different props (shallow
equality). Otherwise, we trust the reactivity
system to make sure that all impacted components
are updated

src/app/template_helpers.ts

@@ -2,6 +2,8 @@ import { BDom, multi, text, toggler } from "../blockdom";
 import { validateProps } from "../component/props_validation";
 import { Markup } from "../utils";
 import { html } from "../blockdom/index";
+import { TARGET } from "../reactivity";
+
 /**
  * This file contains utility functions that will be injected in each template,
  * to perform various useful tasks in the compiled code.
@@ -21,7 +23,8 @@ function callSlot(
   defaultContent?: (ctx: any, node: any, key: string) => BDom
 ): BDom {
   key = key + "__slot_" + name;
-  const slots = (ctx.props && ctx.props.slots) || {};
+  const nonReactiveProps = ctx.props && ctx.props[TARGET];
+  const slots = nonReactiveProps ? nonReactiveProps.slots || {} : {};
   const { __render, __ctx, __scope } = slots[name] || {};
   const slotScope = Object.create(__ctx || {});
   if (__scope) {

src/compiler/code_generator.ts

@@ -1081,11 +1081,9 @@ export class CodeGenerator {
 
     let propString = propStr;
     if (ast.dynamicProps) {
-      if (!props.length) {
-        propString = `${compileExpr(ast.dynamicProps)}`;
-      } else {
-        propString = `Object.assign({}, ${compileExpr(ast.dynamicProps)}, ${propStr})`;
-      }
+      propString = `Object.assign({}, ${compileExpr(ast.dynamicProps)}${
+        props.length ? ", " + propStr : ""
+      })`;
     }
 
     let propVar: string;

src/component/component.ts

@@ -1,14 +1,12 @@
 import type { ComponentNode } from "./component_node";
 
-export type Props = { [key: string]: any };
-
 // -----------------------------------------------------------------------------
 //  Component Class
 // -----------------------------------------------------------------------------
 
 export class Component<Props = any, Env = any> {
   static template: string = "";
-  static props?: Props;
+  static props?: any;
 
   props: Props;
   env: Env;
@@ -22,7 +20,7 @@ export class Component<Props = any, Env = any> {
 
   setup() {}
 
-  render() {
-    this.__owl__.render();
+  render(force: boolean = false) {
+    this.__owl__.render(force);
   }
 }

src/component/component_node.ts

@@ -1,6 +1,6 @@
 import type { App, Env } from "../app/app";
 import { BDom, VNode } from "../blockdom";
-import { clearReactivesForCallback, Reactive, reactive } from "../reactivity";
+import { clearReactivesForCallback, Reactive, reactive, TARGET } from "../reactivity";
 import { batched, Callback } from "../utils";
 import { Component } from "./component";
 import { fibersInError, handleError } from "./error_handling";
@@ -55,7 +55,16 @@ export function useState<T extends object>(state: T): Reactive<T> {
 // -----------------------------------------------------------------------------
 // component function (used in compiled template code)
 // -----------------------------------------------------------------------------
+type Props = { [key: string]: any };
 
+function arePropsDifferent(props1: Props, props2: Props): boolean {
+  for (let k in props1) {
+    if (props1[k] !== props2[k]) {
+      return true;
+    }
+  }
+  return false;
+}
 export function component(
   name: string | typeof Component,
   props: any,
@@ -80,7 +89,10 @@ export function component(
 
   const parentFiber = ctx.fiber!;
   if (node) {
-    node.updateAndRender(props, parentFiber);
+    const currentProps = node.component.props[TARGET];
+    if (parentFiber.force || arePropsDifferent(currentProps, props)) {
+      node.updateAndRender(props, parentFiber);
+    }
   } else {
     // new component
     let C;
@@ -140,6 +152,7 @@ export class ComponentNode<T extends typeof Component = typeof Component>
     applyDefaultProps(props, C);
     const env = (parent && parent.childEnv) || app.env;
     this.childEnv = env;
+    props = useState(props);
     this.component = new C(props, env, this) as any;
     this.renderFn = app.getTemplate(C.template).bind(this.component, this.component, this);
     this.component.setup();
@@ -168,7 +181,7 @@ export class ComponentNode<T extends typeof Component = typeof Component>
     }
   }
 
-  async render() {
+  async render(force: boolean = false) {
     let current = this.fiber;
     if (current && current.root!.locked) {
       await Promise.resolve();
@@ -176,13 +189,15 @@ export class ComponentNode<T extends typeof Component = typeof Component>
       current = this.fiber;
     }
     if (current && !current.bdom && !fibersInError.has(current)) {
-      return;
+      if (current.force || force === false) {
+        return;
+      }
     }
     if (!this.bdom && !current) {
       return;
     }
 
-    const fiber = makeRootFiber(this);
+    const fiber = makeRootFiber(this, force);
     this.fiber = fiber;
     this.app.scheduler.addFiber(fiber);
     await Promise.resolve();
@@ -244,6 +259,9 @@ export class ComponentNode<T extends typeof Component = typeof Component>
     this.fiber = fiber;
     const component = this.component;
     applyDefaultProps(props, component.constructor as any);
+
+    currentNode = this;
+    props = useState(props);
     const prom = Promise.all(this.willUpdateProps.map((f) => f.call(component, props)));
     await prom;
     if (fiber !== this.fiber) {
@@ -308,6 +326,14 @@ export class ComponentNode<T extends typeof Component = typeof Component>
   }
 
   patch() {
+    if (this.fiber && this.fiber.parent) {
+      // we only patch here renderings coming from above. renderings initiated
+      // by the component will be patched independently in the appropriate
+      // fiber.complete
+      this._patch();
+    }
+  }
+  _patch() {
     const hasChildren = Object.keys(this.children).length > 0;
     this.bdom!.patch(this!.fiber!.bdom!, hasChildren);
     if (hasChildren) {

src/component/fibers.ts

@@ -13,7 +13,7 @@ export function makeChildFiber(node: ComponentNode, parent: Fiber): Fiber {
   return new Fiber(node, parent);
 }
 
-export function makeRootFiber(node: ComponentNode): Fiber {
+export function makeRootFiber(node: ComponentNode, force: boolean): Fiber {
   let current = node.fiber;
   if (current) {
     let root = current.root!;
@@ -21,6 +21,7 @@ export function makeRootFiber(node: ComponentNode): Fiber {
     current.children = [];
     root.counter++;
     current.bdom = null;
+    current.force = force;
     if (fibersInError.has(current)) {
       fibersInError.delete(current);
       fibersInError.delete(root);
@@ -35,7 +36,7 @@ export function makeRootFiber(node: ComponentNode): Fiber {
   if (node.patched.length) {
     fiber.patched.push(fiber);
   }
-
+  fiber.force = force;
   return fiber;
 }
 
@@ -62,11 +63,13 @@ export class Fiber {
   parent: Fiber | null;
   children: Fiber[] = [];
   appliedToDom = false;
+  force: boolean = false;
 
   constructor(node: ComponentNode, parent: Fiber | null) {
     this.node = node;
     this.parent = parent;
     if (parent) {
+      this.force = parent.force;
       const root = parent.root!;
       root.counter++;
       this.root = root;
@@ -109,7 +112,7 @@ export class RootFiber extends Fiber {
       current = undefined;
 
       // Step 2: patching the dom
-      node.patch();
+      node._patch();
       this.locked = false;
 
       // Step 4: calling all mounted lifecycle hooks

src/reactivity.ts

@@ -1,7 +1,7 @@
 import { Callback } from "./utils";
 
 // Allows to get the target of a Reactive (used for making a new Reactive from the underlying object)
-const TARGET = Symbol("Target");
+export const TARGET = Symbol("Target");
 // Special key to subscribe to, to be notified of key creation/deletion
 const KEYCHANGES = Symbol("Key changes");
 

tests/components/__snapshots__/basics.test.ts.snap

@@ -968,7 +968,7 @@ exports[`basics update props of component without concrete own node 1`] = `
   
   return function template(ctx, node, key = \\"\\") {
     const tKey_1 = ctx['childProps'].key;
-    let b2 = toggler(tKey_1, component(\`Child\`, ctx['childProps'], tKey_1 + key + \`__1\`, node, ctx));
+    let b2 = toggler(tKey_1, component(\`Child\`, Object.assign({}, ctx['childProps']), tKey_1 + key + \`__1\`, node, ctx));
     return block1([], [b2]);
   }
 }"

tests/components/__snapshots__/concurrency.test.ts.snap

@@ -1145,7 +1145,7 @@ exports[`properly behave when destroyed/unmounted while rendering  2`] = `
   let block1 = createBlock(\`<div><block-child-0/></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let b2 = component(\`SubChild\`, {}, key + \`__1\`, node, ctx);
+    let b2 = component(\`SubChild\`, {val: ctx['props'].val}, key + \`__1\`, node, ctx);
     return block1([], [b2]);
   }
 }"

tests/components/__snapshots__/lifecycle.test.ts.snap

@@ -499,7 +499,7 @@ exports[`lifecycle hooks onWillRender 1`] = `
   let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
   
   return function template(ctx, node, key = \\"\\") {
-    return component(\`Child\`, {}, key + \`__1\`, node, ctx);
+    return component(\`Child\`, {someValue: ctx['state'].value}, key + \`__1\`, node, ctx);
   }
 }"
 `;

tests/components/__snapshots__/rendering.test.ts.snap

@@ -0,0 +1,163 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`force render in case of existing render 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return component(\`B\`, {val: ctx['state'].val}, key + \`__1\`, node, ctx);
+  }
+}"
+`;
+
+exports[`force render in case of existing render 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2 = component(\`C\`, {}, key + \`__1\`, node, ctx);
+    let b3 = text(ctx['props'].val);
+    return multi([b2, b3]);
+  }
+}"
+`;
+
+exports[`force render in case of existing render 3`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(\`C\`);
+  }
+}"
+`;
+
+exports[`rendering semantics can force a render to update sub tree 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2 = text(ctx['state'].value);
+    let b3 = component(\`Child\`, {}, key + \`__1\`, node, ctx);
+    return multi([b2, b3]);
+  }
+}"
+`;
+
+exports[`rendering semantics can force a render to update sub tree 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(\`child\`);
+  }
+}"
+`;
+
+exports[`rendering semantics can render a parent without rendering child 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2 = text(ctx['state'].value);
+    let b3 = component(\`Child\`, {}, key + \`__1\`, node, ctx);
+    return multi([b2, b3]);
+  }
+}"
+`;
+
+exports[`rendering semantics can render a parent without rendering child 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(\`child\`);
+  }
+}"
+`;
+
+exports[`rendering semantics props are reactive (nested prop) 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return component(\`Child\`, {a: ctx['state']}, key + \`__1\`, node, ctx);
+  }
+}"
+`;
+
+exports[`rendering semantics props are reactive (nested prop) 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].a.b.c);
+  }
+}"
+`;
+
+exports[`rendering semantics props are reactive 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return component(\`Child\`, {a: ctx['state']}, key + \`__1\`, node, ctx);
+  }
+}"
+`;
+
+exports[`rendering semantics props are reactive 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].a.b);
+  }
+}"
+`;
+
+exports[`rendering semantics rendering is atomic (for one subtree) 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2 = text(ctx['state'].obj.val);
+    let b3 = component(\`B\`, {obj: ctx['state'].obj}, key + \`__1\`, node, ctx);
+    return multi([b2, b3]);
+  }
+}"
+`;
+
+exports[`rendering semantics rendering is atomic (for one subtree) 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return component(\`C\`, {obj: ctx['props'].obj}, key + \`__1\`, node, ctx);
+  }
+}"
+`;
+
+exports[`rendering semantics rendering is atomic (for one subtree) 3`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].obj.val);
+  }
+}"
+`;

tests/components/__snapshots__/t_props.test.ts.snap

@@ -8,7 +8,7 @@ exports[`t-props basic use 1`] = `
   let block1 = createBlock(\`<div><block-child-0/></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let b2 = component(\`Child\`, ctx['some'].obj, key + \`__1\`, node, ctx);
+    let b2 = component(\`Child\`, Object.assign({}, ctx['some'].obj), key + \`__1\`, node, ctx);
     return block1([], [b2]);
   }
 }"
@@ -65,7 +65,7 @@ exports[`t-props t-props only 1`] = `
   let block1 = createBlock(\`<div><div><block-child-0/></div></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let b2 = component(\`Comp\`, ctx['state'], key + \`__1\`, node, ctx);
+    let b2 = component(\`Comp\`, Object.assign({}, ctx['state']), key + \`__1\`, node, ctx);
     return block1([], [b2]);
   }
 }"

tests/components/basics.test.ts

@@ -121,7 +121,7 @@ describe("basics", () => {
     class Test extends Component {
       static template = xml`<span>simple vnode</span>`;
       setup() {
-        expect(this.props).toBe(p);
+        expect(this.props).not.toBe(p);
       }
     }
 

tests/components/concurrency.test.ts

@@ -39,6 +39,8 @@ Scheduler.prototype.addFiber = function (fiber: Fiber) {
 
 afterEach(() => {
   if (lastScheduler && lastScheduler.tasks.size > 0) {
+    // we still clear the scheduler to prevent additional noise
+    lastScheduler.tasks.clear();
     throw new Error("we got a memory leak...");
   }
 });
@@ -521,7 +523,7 @@ test("properly behave when destroyed/unmounted while rendering ", async () => {
   }
 
   class Child extends Component {
-    static template = xml`<div><SubChild /></div>`;
+    static template = xml`<div><SubChild val="props.val"/></div>`;
     static components = { SubChild };
     setup() {
       useLogLifecycle();
@@ -1907,18 +1909,13 @@ test("concurrent renderings scenario 13", async () => {
   await nextTick(); // wait for this change to be applied
   expect([
     "Parent:willRender",
-    "Child:willUpdateProps",
     "Child:setup",
     "Child:willStart",
     "Parent:rendered",
     "Child:willRender",
     "Child:rendered",
-    "Child:willRender",
-    "Child:rendered",
     "Parent:willPatch",
-    "Child:willPatch",
     "Child:mounted",
-    "Child:patched",
     "Parent:patched",
     "Child:willRender",
     "Child:rendered",
@@ -2472,9 +2469,9 @@ test("two renderings initiated between willPatch and patched", async () => {
       useLogLifecycle();
       onMounted(() => {
         this.mounted = "Mounted";
-        parent.render();
+        parent.render(true);
       });
-      onWillUnmount(() => parent.render());
+      onWillUnmount(() => parent.render(true));
     }
   }
 
@@ -2507,15 +2504,11 @@ test("two renderings initiated between willPatch and patched", async () => {
     "Parent:rendered",
   ]).toBeLogged();
 
+  await nextMicroTick();
+  expect(["Panel:willRender", "Panel:rendered"]).toBeLogged();
+
   await nextTick();
-  expect([
-    "Panel:willRender",
-    "Panel:rendered",
-    "Parent:willPatch",
-    "Panel:willPatch",
-    "Panel:patched",
-    "Parent:patched",
-  ]).toBeLogged();
+  expect(["Parent:willPatch", "Panel:willPatch", "Panel:patched", "Parent:patched"]).toBeLogged();
   expect(fixture.innerHTML).toBe("<div><abc>Panel1Mounted</abc></div>");
 
   parent.state.panel = "Panel2";
@@ -2753,12 +2746,20 @@ test("delay willUpdateProps with rendering grandchild", async () => {
     static template = xml`<Parent state="state"/>`;
     static components = { Parent };
     state = { value: 0 };
+    setup() {
+      useLogLifecycle();
+    }
   }
+
   const parent = await mount(GrandParent, fixture);
   expect(fixture.innerHTML).toBe("0_0<div></div>");
   expect([
+    "GrandParent:setup",
+    "GrandParent:willStart",
+    "GrandParent:willRender",
     "Parent:setup",
     "Parent:willStart",
+    "GrandParent:rendered",
     "Parent:willRender",
     "DelayedChild:setup",
     "DelayedChild:willStart",
@@ -2772,20 +2773,23 @@ test("delay willUpdateProps with rendering grandchild", async () => {
     "ReactiveChild:mounted",
     "DelayedChild:mounted",
     "Parent:mounted",
+    "GrandParent:mounted",
   ]).toBeLogged();
 
   promise = makeDeferred();
   const prom1 = promise;
   parent.state.value = 1;
   child.render(); // trigger a root rendering first
-  parent.render();
+  parent.render(true);
   reactiveChild.render();
   await nextTick();
   expect(fixture.innerHTML).toBe("0_0<div></div>");
   expect([
     "DelayedChild:willRender",
     "DelayedChild:rendered",
+    "GrandParent:willRender",
     "Parent:willUpdateProps",
+    "GrandParent:rendered",
     "ReactiveChild:willRender",
     "ReactiveChild:rendered",
     "Parent:willRender",
@@ -2800,12 +2804,14 @@ test("delay willUpdateProps with rendering grandchild", async () => {
   const prom2 = promise;
   child.render(); // trigger a root rendering first
   parent.state.value = 2;
-  parent.render();
+  parent.render(true);
   reactiveChild.render();
   await nextTick();
   expect(fixture.innerHTML).toBe("0_0<div></div>");
   expect([
+    "GrandParent:willRender",
     "Parent:willUpdateProps",
+    "GrandParent:rendered",
     "ReactiveChild:willRender",
     "ReactiveChild:rendered",
     "Parent:willRender",
@@ -2822,12 +2828,14 @@ test("delay willUpdateProps with rendering grandchild", async () => {
   expect([
     "DelayedChild:willRender",
     "DelayedChild:rendered",
+    "GrandParent:willPatch",
     "Parent:willPatch",
     "ReactiveChild:willPatch",
     "DelayedChild:willPatch",
     "DelayedChild:patched",
     "ReactiveChild:patched",
     "Parent:patched",
+    "GrandParent:patched",
   ]).toBeLogged();
 
   prom1.resolve();

tests/components/hooks.test.ts

@@ -223,7 +223,7 @@ describe("hooks", () => {
     expect(fixture.innerHTML).toBe("<div>maggot brain</div>");
     someVal = "brain";
     someVal2 = "maggot";
-    component.render();
+    component.render(true);
     await nextTick();
     expect(fixture.innerHTML).toBe("<div>brain maggot</div>");
   });

tests/components/lifecycle.test.ts

@@ -849,8 +849,9 @@ describe("lifecycle hooks", () => {
 
     class Parent extends Component {
       static template = xml`
-        <Child />`;
+        <Child someValue="state.value" />`;
       static components = { Child };
+      state = useState({ value: 1 });
       setup() {
         useLogLifecycle();
       }
@@ -871,7 +872,7 @@ describe("lifecycle hooks", () => {
       "Parent:mounted",
     ]).toBeLogged();
 
-    parent.render(); // to block child render
+    parent.state.value++; // to block child render
     await nextTick();
     expect(["Parent:willRender", "Child:willUpdateProps", "Parent:rendered"]).toBeLogged();
 
@@ -1008,20 +1009,15 @@ describe("lifecycle hooks", () => {
     await nextTick();
     expect([
       "C:willRender",
-      "D:willUpdateProps",
       "F:setup",
       "F:willStart",
       "C:rendered",
-      "D:willRender",
-      "D:rendered",
       "F:willRender",
       "F:rendered",
       "C:willPatch",
-      "D:willPatch",
       "E:willUnmount",
       "E:willDestroy",
       "F:mounted",
-      "D:patched",
       "C:patched",
     ]).toBeLogged();
   });

tests/components/rendering.test.ts

@@ -0,0 +1,346 @@
+import { Component, mount, onRendered, onWillUpdateProps, useState, xml } from "../../src";
+import {
+  makeTestFixture,
+  snapshotEverything,
+  nextTick,
+  useLogLifecycle,
+  makeDeferred,
+} from "../helpers";
+
+let fixture: HTMLElement;
+
+snapshotEverything();
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+});
+
+describe("rendering semantics", () => {
+  test("can render a parent without rendering child", async () => {
+    class Child extends Component {
+      static template = xml`child`;
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <t t-esc="state.value"/>
+        <Child/>
+      `;
+      static components = { Child };
+
+      state = useState({ value: "A" });
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    const parent = await mount(Parent, fixture);
+
+    expect(fixture.innerHTML).toBe("Achild");
+    expect([
+      "Parent:setup",
+      "Parent:willStart",
+      "Parent:willRender",
+      "Child:setup",
+      "Child:willStart",
+      "Parent:rendered",
+      "Child:willRender",
+      "Child:rendered",
+      "Child:mounted",
+      "Parent:mounted",
+    ]).toBeLogged();
+
+    parent.state.value = "B";
+    await nextTick();
+    expect(fixture.innerHTML).toBe("Bchild");
+    expect([
+      "Parent:willRender",
+      "Parent:rendered",
+      "Parent:willPatch",
+      "Parent:patched",
+    ]).toBeLogged();
+  });
+
+  test("can force a render to update sub tree", async () => {
+    let childN = 0;
+    let parentN = 0;
+    class Child extends Component {
+      static template = xml`child`;
+      setup() {
+        onRendered(() => childN++);
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <t t-esc="state.value"/>
+        <Child/>
+      `;
+      static components = { Child };
+
+      state = { value: "A" };
+      setup() {
+        onRendered(() => parentN++);
+      }
+    }
+
+    const parent = await mount(Parent, fixture);
+
+    expect(fixture.innerHTML).toBe("Achild");
+    expect(parentN).toBe(1);
+    expect(childN).toBe(1);
+
+    parent.state.value = "B";
+    parent.render(true);
+    await nextTick();
+    expect(fixture.innerHTML).toBe("Bchild");
+    expect(parentN).toBe(2);
+    expect(childN).toBe(2);
+  });
+
+  test("props are reactive", async () => {
+    class Child extends Component {
+      static template = xml`<t t-esc="props.a.b"/>`;
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <Child a="state"/>
+      `;
+      static components = { Child };
+
+      state = useState({ b: 1 });
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    const parent = await mount(Parent, fixture);
+    expect(fixture.innerHTML).toBe("1");
+    expect([
+      "Parent:setup",
+      "Parent:willStart",
+      "Parent:willRender",
+      "Child:setup",
+      "Child:willStart",
+      "Parent:rendered",
+      "Child:willRender",
+      "Child:rendered",
+      "Child:mounted",
+      "Parent:mounted",
+    ]).toBeLogged();
+
+    parent.state.b = 3;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("3");
+    expect(["Child:willRender", "Child:rendered", "Child:willPatch", "Child:patched"]).toBeLogged();
+  });
+
+  test("props are reactive (nested prop)", async () => {
+    class Child extends Component {
+      static template = xml`<t t-esc="props.a.b.c"/>`;
+
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <Child a="state"/>
+      `;
+      static components = { Child };
+
+      state = useState({ b: { c: 1 } });
+
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    const parent = await mount(Parent, fixture);
+    expect(fixture.innerHTML).toBe("1");
+    expect([
+      "Parent:setup",
+      "Parent:willStart",
+      "Parent:willRender",
+      "Child:setup",
+      "Child:willStart",
+      "Parent:rendered",
+      "Child:willRender",
+      "Child:rendered",
+      "Child:mounted",
+      "Parent:mounted",
+    ]).toBeLogged();
+
+    parent.state.b.c = 3; // parent is now subscribed to 'b' key
+    await nextTick();
+    expect(fixture.innerHTML).toBe("3");
+    expect(["Child:willRender", "Child:rendered", "Child:willPatch", "Child:patched"]).toBeLogged();
+
+    parent.state.b = { c: 444 }; // triggers a parent and a child render
+    await nextTick();
+    expect(fixture.innerHTML).toBe("444");
+    expect([
+      "Parent:willRender",
+      "Parent:rendered",
+      "Child:willRender",
+      "Child:rendered",
+      "Parent:willPatch",
+      "Parent:patched",
+      "Child:willPatch",
+      "Child:patched",
+    ]).toBeLogged();
+  });
+
+  test("rendering is atomic (for one subtree)", async () => {
+    const def = makeDeferred();
+
+    class C extends Component {
+      static template = xml`<t t-esc="props.obj.val"/>`;
+
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    class B extends Component {
+      static template = xml`<C obj="props.obj"/>`;
+      static components = { C };
+
+      setup() {
+        useLogLifecycle();
+        onWillUpdateProps(() => def);
+      }
+    }
+
+    class A extends Component {
+      static template = xml`<t t-esc="state.obj.val"/><B obj="state.obj"/>`;
+      static components = { B };
+
+      state = useState({ obj: { val: 1 } });
+
+      setup() {
+        useLogLifecycle();
+      }
+    }
+
+    const parent = await mount(A, fixture);
+    expect(fixture.innerHTML).toBe("11");
+    expect([
+      "A:setup",
+      "A:willStart",
+      "A:willRender",
+      "B:setup",
+      "B:willStart",
+      "A:rendered",
+      "B:willRender",
+      "C:setup",
+      "C:willStart",
+      "B:rendered",
+      "C:willRender",
+      "C:rendered",
+      "C:mounted",
+      "B:mounted",
+      "A:mounted",
+    ]).toBeLogged();
+
+    parent.state.obj.val = 3;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("33");
+    expect([
+      "A:willRender",
+      "A:rendered",
+      "C:willRender",
+      "C:rendered",
+      "A:willPatch",
+      "A:patched",
+      "C:willPatch",
+      "C:patched",
+    ]).toBeLogged();
+
+    def.resolve();
+    await nextTick();
+    expect([]).toBeLogged();
+  });
+});
+
+test("force render in case of existing render", async () => {
+  const def = makeDeferred();
+
+  class C extends Component {
+    static template = xml`C`;
+    setup() {
+      useLogLifecycle();
+    }
+  }
+  class B extends Component {
+    static template = xml`<C/><t t-esc="props.val"/>`;
+    static components = { C };
+    setup() {
+      useLogLifecycle();
+      onWillUpdateProps(() => def);
+    }
+  }
+  class A extends Component {
+    static template = xml`<B val="state.val"/>`;
+    static components = { B };
+    state = useState({ val: 1 });
+    setup() {
+      useLogLifecycle();
+    }
+  }
+  const parent = await mount(A, fixture);
+  expect(fixture.innerHTML).toBe("C1");
+  expect([
+    "A:setup",
+    "A:willStart",
+    "A:willRender",
+    "B:setup",
+    "B:willStart",
+    "A:rendered",
+    "B:willRender",
+    "C:setup",
+    "C:willStart",
+    "B:rendered",
+    "C:willRender",
+    "C:rendered",
+    "C:mounted",
+    "B:mounted",
+    "A:mounted",
+  ]).toBeLogged();
+
+  // trigger a new rendering, blocked in B
+  parent.state.val = 2;
+  await nextTick();
+  expect(["A:willRender", "B:willUpdateProps", "A:rendered"]).toBeLogged();
+
+  // initiate a new render with force=true. it should cancel the current render
+  // and also be blocked in B
+  parent.render(true);
+  await nextTick();
+  expect(["A:willRender", "B:willUpdateProps", "A:rendered"]).toBeLogged();
+
+  def.resolve();
+  await nextTick();
+  // we check here that the render reaches C (so, that it was properly forced)
+  expect([
+    "B:willRender",
+    "C:willUpdateProps",
+    "B:rendered",
+    "C:willRender",
+    "C:rendered",
+    "A:willPatch",
+    "B:willPatch",
+    "C:willPatch",
+    "C:patched",
+    "B:patched",
+    "A:patched",
+  ]).toBeLogged();
+});

tests/components/t_props.test.ts

@@ -65,7 +65,7 @@ describe("t-props", () => {
         `;
       setup() {
         expect(this.props).toEqual({ a: 1, b: 2 });
-        expect(this.props).toBe(props);
+        expect(this.props).not.toBe(props);
       }
     }
     class Parent extends Component {

tests/reactivity.test.ts

@@ -1612,7 +1612,7 @@ describe("Reactivity: useState", () => {
     expect([...steps]).toEqual(["list"]);
     await nextTick();
     expect(fixture.innerHTML).toBe("<div><div>3</div> Total: 3 Count: 1</div>");
-    expect([...steps]).toEqual(["list", "quantity1"]);
+    expect([...steps]).toEqual(["list"]);
     steps.clear();
 
     secondQuantity.quantity = 2;