[FIX] component: concurrent calls to mount and render

Closes #450

src/component/component.ts

@@ -1,6 +1,6 @@
 import { Observer } from "../core/observer";
 import { CompiledTemplate, QWeb } from "../qweb/index";
-import { h, patch, VNode } from "../vdom/index";
+import { patch, VNode } from "../vdom/index";
 import "./directive";
 import { Fiber } from "./fiber";
 import "./props_validation";
@@ -282,32 +282,19 @@ export class Component<T extends Env, Props extends {}> {
       return Promise.resolve();
     }
     if (!(target instanceof HTMLElement)) {
-      let message = `Component '${this.constructor.name}' cannot be mounted: the target is not a valid DOM node.`;
+      let message = `Component '${
+        this.constructor.name
+      }' cannot be mounted: the target is not a valid DOM node.`;
       message += `\nMaybe the DOM is not ready yet? (in that case, you can use owl.utils.whenReady)`;
       throw new Error(message);
     }
-    return new Promise((resolve, reject) => {
+    const fiber = new Fiber(null, this, undefined, undefined, false, target);
-      const fiber = new Fiber(null, this, undefined, undefined, false);
+    if (!__owl__.vnode) {
-      scheduler.addFiber(fiber, err => {
+      this.__prepareAndRender(fiber);
-        if (err) {
+    } else {
-          reject(err);
+      this.__render(fiber);
-          return;
+    }
-        }
+    return scheduler.addFiber(fiber);
-        if (!__owl__.isDestroyed) {
-          this.__patch(fiber.vnode);
-          target.appendChild(this.el!);
-          if (document.body.contains(target)) {
-            this.__callMounted();
-          }
-        }
-        resolve();
-      });
-      if (!__owl__.vnode) {
-        this.__prepareAndRender(fiber);
-      } else {
-        this.__render(fiber);
-      }
-    });
   }
 
   /**
@@ -332,26 +319,18 @@ export class Component<T extends Env, Props extends {}> {
    */
   async render(force: boolean = false): Promise<void> {
     const __owl__ = this.__owl__;
-    if (
+    if (!__owl__.isMounted && !__owl__.currentFiber) {
-      (!__owl__.isMounted && !__owl__.currentFiber) ||
+      // if we get here, this means that the component was either never mounted,
-      (__owl__.currentFiber && !__owl__.currentFiber.isRendered)
+      // or was unmounted and some state change  triggered a render. Either way,
-    ) {
+      // we do not want to actually render anything in this case.
       return;
     }
-    return new Promise((resolve, reject) => {
+    if (__owl__.currentFiber && !__owl__.currentFiber.isRendered) {
-      const fiber = new Fiber(null, this, undefined, undefined, force);
+      return scheduler.addFiber(__owl__.currentFiber.root);
-      scheduler.addFiber(fiber.root, err => {
+    }
-        if (err) {
+    const fiber = new Fiber(null, this, undefined, undefined, force, null);
-          reject(err);
+    this.__render(fiber);
-          return;
+    return scheduler.addFiber(fiber);
-        }
-        if (__owl__.isMounted && fiber === fiber.root) {
-          fiber.patchComponents();
-        }
-        resolve();
-      });
-      this.__render(fiber);
-    });
   }
 
   /**
@@ -437,7 +416,7 @@ export class Component<T extends Env, Props extends {}> {
     __owl__.isDestroyed = true;
     delete __owl__.vnode;
     if (__owl__.currentFiber) {
-      __owl__.currentFiber.isCancelled = true;
+      __owl__.currentFiber.isCompleted = true;
     }
   }
 
@@ -492,7 +471,7 @@ export class Component<T extends Env, Props extends {}> {
     const shouldUpdate = parentFiber.force || this.shouldUpdate(nextProps);
     if (shouldUpdate) {
       const __owl__ = this.__owl__;
-      const fiber = new Fiber(parentFiber, this, scope, vars, parentFiber.force);
+      const fiber = new Fiber(parentFiber, this, scope, vars, parentFiber.force, null);
       if (!parentFiber.child) {
         parentFiber.child = fiber;
       } else {
@@ -510,7 +489,7 @@ export class Component<T extends Env, Props extends {}> {
         this.willUpdateProps(nextProps),
         __owl__.willUpdatePropsCB && __owl__.willUpdatePropsCB(nextProps)
       ]);
-      if (fiber.isCancelled) {
+      if (fiber.isCompleted) {
         return;
       }
       this.props = nextProps;
@@ -535,7 +514,7 @@ export class Component<T extends Env, Props extends {}> {
    * parent template.
    */
   __prepare(parentFiber: Fiber, scope: any, vars: any, previousSibling?: Fiber | null) {
-    const fiber = new Fiber(parentFiber, this, scope, vars, parentFiber.force);
+    const fiber = new Fiber(parentFiber, this, scope, vars, parentFiber.force, null);
     fiber.shouldPatch = false;
     if (!parentFiber.child) {
       parentFiber.child = fiber;
@@ -569,13 +548,12 @@ export class Component<T extends Env, Props extends {}> {
       await Promise.all([this.willStart(), this.__owl__.willStartCB && this.__owl__.willStartCB()]);
     } catch (e) {
       fiber.handleError(e);
-      fiber.vnode = h("div"); // -> we render this div at the end
       return Promise.resolve();
     }
     if (this.__owl__.isDestroyed) {
       return Promise.resolve();
     }
-    if (!fiber.isCancelled) {
+    if (!fiber.isCompleted) {
       this.__render(fiber);
     }
   }
@@ -585,17 +563,14 @@ export class Component<T extends Env, Props extends {}> {
     if (__owl__.observer) {
       __owl__.observer.allowMutations = false;
     }
-    let vnode;
     try {
-      vnode = __owl__.renderFn!(this, {
+      fiber.vnode = __owl__.renderFn!(this, {
         handlers: __owl__.boundHandlers,
         fiber: fiber
       });
     } catch (e) {
-      vnode = __owl__.vnode || h("div");
       fiber.handleError(e);
     }
-    fiber.vnode = vnode;
     if (__owl__.observer) {
       __owl__.observer.allowMutations = true;
     }
@@ -604,7 +579,8 @@ export class Component<T extends Env, Props extends {}> {
     // template (so, something like <MyComponent class="..."/>) to the actual
     // root vnode
     if (__owl__.classObj) {
-      vnode.data.class = Object.assign(vnode.data.class || {}, __owl__.classObj);
+      const data = fiber.vnode!.data!;
+      data.class = Object.assign(data.class || {}, __owl__.classObj);
     }
     fiber.root.counter--;
     fiber.isRendered = true;

src/component/directive.ts

@@ -455,7 +455,7 @@ QWeb.addDirective({
     );
     ctx.addLine(`const fiber = w${componentID}.__owl__.currentFiber;`);
     ctx.addLine(
-      `def${defID}.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; ${createHook}});`
+      `def${defID}.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; ${createHook}});`
     );
     if (registerCode) {
       ctx.addLine(registerCode);

src/component/fiber.ts

@@ -1,4 +1,4 @@
-import { VNode } from "../vdom/index";
+import { h, VNode } from "../vdom/index";
 import { Component } from "./component";
 import { scheduler } from "./scheduler";
 
@@ -20,9 +20,10 @@ export class Fiber {
   // method potentially implemented by a component. It is usually set to false.
   force: boolean;
 
-  // isCancelled means that the rendering corresponding to this fiber and its
+  // isCompleted means that the rendering corresponding to this fiber's work is
-  // children is cancelled. No extra work should be done.
+  // done, either because the component has been mounted or patched, or because
-  isCancelled: boolean = false;
+  // fiber has been cancelled.
+  isCompleted: boolean = false;
 
   // the fibers corresponding to component updates (updateProps) need to call
   // the willPatch and patched hooks from the corresponding component. However,
@@ -42,6 +43,8 @@ export class Fiber {
   // scheduler.
   counter: number = 0;
 
+  target: HTMLElement | null;
+
   scope: any;
   vars: any;
 
@@ -55,18 +58,25 @@ export class Fiber {
 
   error?: Error;
 
-  constructor(parent: Fiber | null, component: Component<any, any>, scope, vars, force) {
+  constructor(parent: Fiber | null, component: Component<any, any>, scope, vars, force, target) {
     this.force = force;
     this.scope = scope;
     this.vars = vars;
     this.component = component;
+    this.target = target;
 
     this.root = parent ? parent.root : this;
     this.parent = parent;
 
     let oldFiber = component.__owl__.currentFiber;
-    if (oldFiber && !oldFiber.isCancelled) {
+    if (oldFiber && !oldFiber.isCompleted) {
-      this._remapFiber(oldFiber);
+      if (oldFiber.root === oldFiber && !parent) {
+        // both oldFiber and this fiber are root fibers
+        this._reuseFiber(oldFiber);
+        return oldFiber;
+      } else {
+        this._remapFiber(oldFiber);
+      }
     }
 
     this.root.counter++;
@@ -74,6 +84,25 @@ export class Fiber {
     component.__owl__.currentFiber = this;
   }
 
+  /**
+   * When the oldFiber is not completed yet, and both oldFiber and this fiber
+   * are root fibers, we want to reuse the oldFiber instead of creating a new
+   * one. Doing so will guarantee that the initiator(s) of those renderings will
+   * be notified (the promise will resolve) when the last rendering will be done.
+   *
+   * This function thus assumes that oldFiber is a root fiber.
+   */
+  _reuseFiber(oldFiber: Fiber) {
+    oldFiber.cancel(); // cancel children fibers
+    oldFiber.isCompleted = false; // keep the root fiber alive
+    if (oldFiber.child) {
+      // remove relation to children
+      oldFiber.child.parent = null;
+      oldFiber.child = null;
+    }
+    oldFiber.counter = 1; // re-initialize counter
+  }
+
   /**
    * In some cases, a rendering initiated at some component can detect that it
    * should be part of a larger rendering initiated somewhere up the component
@@ -83,7 +112,7 @@ export class Fiber {
   _remapFiber(oldFiber: Fiber) {
     oldFiber.cancel();
     if (oldFiber === oldFiber.root) {
-      oldFiber.root.counter++;
+      oldFiber.counter++;
     }
     if (oldFiber.parent && !this.parent) {
       // re-map links
@@ -132,7 +161,28 @@ export class Fiber {
   }
 
   /**
-   * Apply the given patch queue from a fiber.
+   * Successfully complete the work of the fiber: call the mount or patch hooks
+   * and patch the DOM. This function is called once the fiber and its children
+   * are ready, and the scheduler decides to process it.
+   */
+  complete() {
+    const component = this.component;
+    if (this.target) {
+      component.__patch(this.vnode);
+      this.target.appendChild(component.el!);
+      if (document.body.contains(this.target)) {
+        component.__callMounted();
+      }
+    } else {
+      if (component.__owl__.isMounted && this === this.root) {
+        this.patchComponents();
+      }
+    }
+    this.isCompleted = true;
+  }
+
+  /**
+   * Compute and apply the patch queue of the fiber.
    *   1) Call 'willPatch' on the component of each patch
    *   2) Call '__patch' on the component of each patch
    *   3) Call 'patched' on the component of each patch, in reverse order
@@ -142,8 +192,8 @@ export class Fiber {
     const doWork: (Fiber) => Fiber | null = function(f) {
       if (f.shouldPatch) {
         patchQueue.push(f);
+        return f.child;
       }
-      return f.child;
     };
     this._walk(doWork);
     let component: Component<any, any> = this.component;
@@ -186,7 +236,7 @@ export class Fiber {
       if (!f.isRendered) {
         f.root.counter--;
       }
-      f.isCancelled = true;
+      f.isCompleted = true;
       return f.child;
     });
   }
@@ -200,10 +250,12 @@ export class Fiber {
    * being in a corrupted state.
    */
   handleError(error: Error) {
-    let canCatch = false;
     let component = this.component;
-    let qweb = component.env.qweb;
+    this.vnode = component.__owl__.vnode || h("div");
+
+    const qweb = component.env.qweb;
     let root = component;
+    let canCatch = false;
     while (component && !(canCatch = !!component.catchError)) {
       root = component;
       component = component.__owl__.parent!;

src/component/scheduler.ts

@@ -25,12 +25,25 @@ export class Scheduler {
     this.requestAnimationFrame = requestAnimationFrame;
   }
 
-  addFiber(fiber, callback) {
+  addFiber(fiber): Promise<void> {
-    this.tasks.push({ fiber, callback });
+    return new Promise((resolve, reject) => {
-    if (this.isRunning) {
+      if (fiber.error) {
-      return;
+        return reject(fiber.error);
-    }
+      }
-    this.scheduleTasks();
+      this.tasks.push({
+        fiber,
+        callback: () => {
+          if (fiber.error) {
+            reject(fiber.error);
+            return;
+          }
+          resolve();
+        }
+      });
+      if (!this.isRunning) {
+        this.scheduleTasks();
+      }
+    });
   }
 
   /**
@@ -41,11 +54,15 @@ export class Scheduler {
     let tasks = this.tasks;
     this.tasks = [];
     tasks = tasks.filter(task => {
-      if (task.fiber.isCancelled) {
+      if (task.fiber.isCompleted) {
+        task.callback();
         return false;
       }
       if (task.fiber.counter === 0) {
-        task.callback(task.fiber.error);
+        if (!task.fiber.error) {
+          task.fiber.complete();
+        }
+        task.callback();
         return false;
       }
       return true;

src/hooks.ts

@@ -24,9 +24,19 @@ import { Observer } from "./core/observer";
 export function useState<T>(state: T): T {
   const component: Component<any, any> = Component.current!;
   const __owl__ = component.__owl__;
+  const renderFn = __owl__.renderFn;
+  let lastRenderRevNumber;
+  __owl__.renderFn = function(comp, params) {
+    lastRenderRevNumber = __owl__.observer!.rev;
+    return renderFn(comp, params);
+  };
   if (!__owl__.observer) {
     __owl__.observer = new Observer();
-    __owl__.observer.notifyCB = component.render.bind(component);
+    __owl__.observer.notifyCB = () => {
+      if (lastRenderRevNumber < __owl__.observer!.rev) {
+        component.render();
+      }
+    };
   }
   return __owl__.observer.observe(state);
 }

src/qweb/base_directives.ts

@@ -236,7 +236,9 @@ QWeb.addDirective({
         varCode = `{${content}}`;
       }
       ctx.addLine(
-        `this.recursiveFns['${subTemplateName}'].call(this, context, Object.assign({}, extra, {parentNode: c${ctx.parentNode}, fiber: {vars: ${varCode}, scope}}));`
+        `this.recursiveFns['${subTemplateName}'].call(this, context, Object.assign({}, extra, {parentNode: c${
+          ctx.parentNode
+        }, fiber: {vars: ${varCode}, scope}}));`
       );
       return true;
     }
@@ -305,7 +307,9 @@ QWeb.addDirective({
       !node.children[0].hasAttribute("t-key");
     if (shouldWarn) {
       console.warn(
-        `Directive t-foreach should always be used with a t-key! (in template: '${ctx.templateName}')`
+        `Directive t-foreach should always be used with a t-key! (in template: '${
+          ctx.templateName
+        }')`
       );
     }
 

tests/__snapshots__/animations.test.ts.snap

@@ -35,7 +35,7 @@ exports[`animations t-transition combined with component 1`] = `
         };
         utils.transitionRemove(vn, 'chimay', finalize);}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -80,7 +80,7 @@ exports[`animations t-transition combined with t-component and t-if 1`] = `
         };
         utils.transitionRemove(vn, 'chimay', finalize);}}});
             const fiber = w3.__owl__.currentFiber;
-            def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             c1.push(pvnode);
             w3.__owl__.pvnode = pvnode;
         }

tests/component/__snapshots__/component.test.ts.snap

@@ -61,7 +61,7 @@ exports[`basic widget properties reconciliation alg works for t-foreach in t-for
                 let def8 = w9.__prepare(extra.fiber, undefined, undefined, sibling);
                 let pvnode = h('dummy', {key: templateId9, hook: {insert(vn) { let nvn=w9.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w9.destroy();}}});
                 const fiber = w9.__owl__.currentFiber;
-                def8.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+                def8.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
                 c1.push(pvnode);
                 w9.__owl__.pvnode = pvnode;
             }
@@ -105,7 +105,7 @@ exports[`class and style attributes with t-component dynamic t-att-style is prop
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.style = _5;}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.style = _5;}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -150,7 +150,7 @@ exports[`class and style attributes with t-component t-att-class is properly add
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;context.__owl__.refs[ref5] = w3;},remove() {},destroy(vn) {w3.destroy();delete context.__owl__.refs[ref5];}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -210,7 +210,7 @@ exports[`class and style attributes with t-component t-att-class is properly add
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;context.__owl__.refs[ref5] = w3;},remove() {},destroy(vn) {w3.destroy();delete context.__owl__.refs[ref5];}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -282,7 +282,7 @@ exports[`composition sub components with some state rendered in a loop 1`] = `
             let def6 = w7.__prepare(extra.fiber, undefined, undefined, sibling);
             let pvnode = h('dummy', {key: templateId7, hook: {insert(vn) { let nvn=w7.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w7.destroy();}}});
             const fiber = w7.__owl__.currentFiber;
-            def6.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def6.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             c1.push(pvnode);
             w7.__owl__.pvnode = pvnode;
         }
@@ -324,7 +324,7 @@ exports[`composition t-component with dynamic value 1`] = `
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -365,7 +365,7 @@ exports[`composition t-component with dynamic value 2 1`] = `
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -406,7 +406,7 @@ exports[`dynamic t-props basic use 1`] = `
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -451,7 +451,7 @@ exports[`other directives with t-component t-on with getter as handler 1`] = `
         let def3 = w4.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId4, hook: {insert(vn) { let nvn=w4.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w4.destroy();}}});
         const fiber = w4.__owl__.currentFiber;
-        def3.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['handler'];if (fn) { fn.call(owner, e); } else { owner.handler; }});}};});
+        def3.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['handler'];if (fn) { fn.call(owner, e); } else { owner.handler; }});}};});
         c1.push(pvnode);
         w4.__owl__.pvnode = pvnode;
     }
@@ -492,7 +492,7 @@ exports[`other directives with t-component t-on with handler bound to argument 1
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, 3, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, 3, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -533,7 +533,7 @@ exports[`other directives with t-component t-on with handler bound to empty obje
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, {}, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, {}, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -574,7 +574,7 @@ exports[`other directives with t-component t-on with handler bound to empty obje
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, {}, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, {}, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -615,7 +615,7 @@ exports[`other directives with t-component t-on with handler bound to object 1`]
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, {val:3}, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, {val:3}, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -660,7 +660,7 @@ exports[`other directives with t-component t-on with inline statement 1`] = `
         let def3 = w4.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId4, hook: {insert(vn) { let nvn=w4.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w4.destroy();}}});
         const fiber = w4.__owl__.currentFiber;
-        def3.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['state.counter++'];if (fn) { fn.call(owner, e); } else { owner.state.counter++; }});}};});
+        def3.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['state.counter++'];if (fn) { fn.call(owner, e); } else { owner.state.counter++; }});}};});
         c1.push(pvnode);
         w4.__owl__.pvnode = pvnode;
     }
@@ -701,7 +701,7 @@ exports[`other directives with t-component t-on with no handler (only modifiers)
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -742,7 +742,7 @@ exports[`other directives with t-component t-on with prevent and self modifiers
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {e.preventDefault();if (e.target !== vn.elm) {return}const fn = owner['onEv'];if (fn) { fn.call(owner, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {e.preventDefault();if (e.target !== vn.elm) {return}const fn = owner['onEv'];if (fn) { fn.call(owner, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -783,7 +783,7 @@ exports[`other directives with t-component t-on with self and prevent modifiers
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {if (e.target !== vn.elm) {return}e.preventDefault();const fn = owner['onEv'];if (fn) { fn.call(owner, e); } else { owner.onEv; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {if (e.target !== vn.elm) {return}e.preventDefault();const fn = owner['onEv'];if (fn) { fn.call(owner, e); } else { owner.onEv; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -824,7 +824,7 @@ exports[`other directives with t-component t-on with self modifier 1`] = `
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev-1', function (e) {const fn = owner['onEv1'];if (fn) { fn.call(owner, e); } else { owner.onEv1; }});vn.elm.addEventListener('ev-2', function (e) {if (e.target !== vn.elm) {return}const fn = owner['onEv2'];if (fn) { fn.call(owner, e); } else { owner.onEv2; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev-1', function (e) {const fn = owner['onEv1'];if (fn) { fn.call(owner, e); } else { owner.onEv1; }});vn.elm.addEventListener('ev-2', function (e) {if (e.target !== vn.elm) {return}const fn = owner['onEv2'];if (fn) { fn.call(owner, e); } else { owner.onEv2; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -865,7 +865,7 @@ exports[`other directives with t-component t-on with stop and/or prevent modifie
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev-1', function (e) {e.stopPropagation();const fn = owner['onEv1'];if (fn) { fn.call(owner, e); } else { owner.onEv1; }});vn.elm.addEventListener('ev-2', function (e) {e.preventDefault();const fn = owner['onEv2'];if (fn) { fn.call(owner, e); } else { owner.onEv2; }});vn.elm.addEventListener('ev-3', function (e) {e.stopPropagation();e.preventDefault();const fn = owner['onEv3'];if (fn) { fn.call(owner, e); } else { owner.onEv3; }});}};});
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev-1', function (e) {e.stopPropagation();const fn = owner['onEv1'];if (fn) { fn.call(owner, e); } else { owner.onEv1; }});vn.elm.addEventListener('ev-2', function (e) {e.preventDefault();const fn = owner['onEv2'];if (fn) { fn.call(owner, e); } else { owner.onEv2; }});vn.elm.addEventListener('ev-3', function (e) {e.stopPropagation();e.preventDefault();const fn = owner['onEv3'];if (fn) { fn.call(owner, e); } else { owner.onEv3; }});}};});
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -925,7 +925,7 @@ exports[`random stuff/miscellaneous snapshotting compiled code 1`] = `
         let def3 = w4.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId4, hook: {insert(vn) { let nvn=w4.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w4.destroy();}}});
         const fiber = w4.__owl__.currentFiber;
-        def3.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def3.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w4.__owl__.pvnode = pvnode;
     }
@@ -983,7 +983,7 @@ exports[`random stuff/miscellaneous t-on with handler bound to dynamic argument
             let def6 = w7.__prepare(extra.fiber, undefined, undefined, sibling);
             let pvnode = h('dummy', {key: templateId7, hook: {insert(vn) { let nvn=w7.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w7.destroy();}}});
             const fiber = w7.__owl__.currentFiber;
-            def6.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, arg9, e); } else { owner.onEv; }});}};});
+            def6.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; vnode.data.hook = {create(_, vn){vn.elm.addEventListener('ev', function (e) {const fn = owner['onEv'];if (fn) { fn.call(owner, arg9, e); } else { owner.onEv; }});}};});
             c1.push(pvnode);
             w7.__owl__.pvnode = pvnode;
         }
@@ -1231,7 +1231,7 @@ exports[`t-slot directive can define and call slots 1`] = `
         let def2 = w3.__prepare(extra.fiber, {}, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }
@@ -1477,7 +1477,7 @@ exports[`t-slot directive slots are rendered with proper context, part 2 2`] = `
             let def8 = w9.__prepare(extra.fiber, Object.assign({}, scope), undefined, sibling);
             let pvnode = h('dummy', {key: templateId9, hook: {insert(vn) { let nvn=w9.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w9.destroy();}}});
             const fiber = w9.__owl__.currentFiber;
-            def8.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def8.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             c7.push(pvnode);
             w9.__owl__.pvnode = pvnode;
         }
@@ -1581,7 +1581,7 @@ exports[`t-slot directive slots are rendered with proper context, part 3 2`] = `
             let def9 = w10.__prepare(extra.fiber, Object.assign({}, scope), {_8}, sibling);
             let pvnode = h('dummy', {key: templateId10, hook: {insert(vn) { let nvn=w10.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w10.destroy();}}});
             const fiber = w10.__owl__.currentFiber;
-            def9.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def9.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             c7.push(pvnode);
             w10.__owl__.pvnode = pvnode;
         }
@@ -1639,7 +1639,7 @@ exports[`t-slot directive slots are rendered with proper context, part 4 1`] = `
         let def3 = w4.__prepare(extra.fiber, {}, {_2}, sibling);
         let pvnode = h('dummy', {key: templateId4, hook: {insert(vn) { let nvn=w4.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w4.destroy();}}});
         const fiber = w4.__owl__.currentFiber;
-        def3.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def3.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w4.__owl__.pvnode = pvnode;
     }
@@ -1714,7 +1714,7 @@ exports[`top level sub widgets basic use 1`] = `
         let def1 = w2.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId2, hook: {insert(vn) { let nvn=w2.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w2.destroy();}}});
         const fiber = w2.__owl__.currentFiber;
-        def1.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def1.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         utils.defineProxy(vn4, pvnode);
         w2.__owl__.pvnode = pvnode;
     }
@@ -1757,7 +1757,7 @@ exports[`top level sub widgets can select a sub widget  1`] = `
             let def1 = w2.__prepare(extra.fiber, undefined, undefined, sibling);
             let pvnode = h('dummy', {key: templateId2, hook: {insert(vn) { let nvn=w2.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w2.destroy();}}});
             const fiber = w2.__owl__.currentFiber;
-            def1.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def1.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             utils.defineProxy(vn4, pvnode);
             w2.__owl__.pvnode = pvnode;
         }
@@ -1787,7 +1787,7 @@ exports[`top level sub widgets can select a sub widget  1`] = `
             let def5 = w6.__prepare(extra.fiber, undefined, undefined, sibling);
             let pvnode = h('dummy', {key: templateId6, hook: {insert(vn) { let nvn=w6.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w6.destroy();}}});
             const fiber = w6.__owl__.currentFiber;
-            def5.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def5.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             utils.defineProxy(vn8, pvnode);
             w6.__owl__.pvnode = pvnode;
         }

tests/component/__snapshots__/props_validation.test.ts.snap

@@ -32,7 +32,7 @@ exports[`props validation props are validated in dev mode (code snapshot) 1`] =
         let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
         let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
         const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
         w3.__owl__.pvnode = pvnode;
     }

tests/component/component.test.ts

@@ -3348,7 +3348,6 @@ describe("async rendering", () => {
     const componentA = new ComponentA();
     await componentA.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><p></p></div>");
-
     stateB.hasChild = true;
     await nextTick();
     expect(fixture.innerHTML).toBe("<div><p></p></div>");
@@ -3363,6 +3362,64 @@ describe("async rendering", () => {
     expect(fixture.innerHTML).toBe("<div><p><span>2</span></p></div>");
     expect(ComponentC.prototype.__render).toHaveBeenCalledTimes(1);
   });
+
+  test("concurrent renderings scenario 11", async () => {
+    // This scenario is the following: we have a component being updated (by props),
+    // and then rendered (render method), but before the willUpdateProps resolves.
+    // We check that in that case, the return value of the render method is a promise
+    // that is resolved when the component is completely rendered (so, properly
+    // remapped to the promise of the ambient rendering)
+    const def = makeDeferred();
+    let child;
+    class Child extends Component<any, any> {
+      static template = xml`<span><t t-esc="props.val"/>|<t t-esc="val"/></span>`;
+      val = 3;
+      willUpdateProps() {
+        child = this;
+        return def;
+      }
+    }
+
+    class Parent extends Component<any, any> {
+      static template = xml`<div><Child val="state.valA"/></div>`;
+      static components = { Child };
+      state = useState({ valA: 1 });
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>1|3</span></div>");
+    parent.state.valA = 2;
+
+    await nextTick();
+    setTimeout(() => {
+      def.resolve();
+    }, 20);
+    child.val = 5;
+    await child.render();
+    expect(fixture.innerHTML).toBe("<div><span>2|5</span></div>");
+  });
+
+  test("change state and call manually render: no unnecessary rendering", async () => {
+    // when the state is changed, the component isn't notified directly (we wait
+    // for a microtask tick before calling 'render'), so it may happen that
+    // another rendering is done meanwhile, already using the new value of the
+    // state
+    class Widget extends Component<any, any> {
+      static template = xml`<div><t t-esc="state.val"/></div>`;
+      state = useState({ val: 1 });
+    }
+    Widget.prototype.__render = jest.fn(Widget.prototype.__render);
+
+    const widget = new Widget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>1</div>");
+    expect(Widget.prototype.__render).toHaveBeenCalledTimes(1);
+
+    widget.state.val = 2;
+    await widget.render();
+    expect(fixture.innerHTML).toBe("<div>2</div>");
+    expect(Widget.prototype.__render).toHaveBeenCalledTimes(2);
+  });
 });
 
 describe("widget and observable state", () => {
@@ -4890,7 +4947,7 @@ describe("unmounting and remounting", () => {
     expect(fixture.innerHTML).toBe("<div>3</div>");
   });
 
-  test("sub component is still active after being  unmounted and remounted", async () => {
+  test("sub component is still active after being unmounted and remounted", async () => {
     class Child extends Component<any, any> {
       static template = xml`
         <p t-on-click="state.value++">
@@ -4920,6 +4977,70 @@ describe("unmounting and remounting", () => {
     await nextTick();
     expect(fixture.innerHTML).toBe("<div><p>3</p></div>");
   });
+
+  test("change state just before mounting component", async () => {
+    const steps: number[] = [];
+    class TestWidget extends Component<any, any> {
+      static template = xml`
+        <div><t t-esc="state.val"/></div>
+      `;
+      state = useState({ val: 1 });
+      __render(f) {
+        steps.push(this.state.val);
+        return super.__render(f);
+      }
+    }
+    TestWidget.prototype.__render = jest.fn(TestWidget.prototype.__render);
+
+    const widget = new TestWidget();
+    widget.state.val = 2;
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>2</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(1);
+
+    // unmount and re-mount, as in this case, willStart won't be called, so it's
+    // slightly different
+    widget.unmount();
+    widget.state.val = 3;
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(2);
+    expect(steps).toEqual([2, 3]);
+  });
+
+  test("change state while mounting component", async () => {
+    const steps: number[] = [];
+    class TestWidget extends Component<any, any> {
+      static template = xml`
+        <div><t t-esc="state.val"/></div>
+      `;
+      state = useState({ val: 1 });
+      __render(f) {
+        steps.push(this.state.val);
+        return super.__render(f);
+      }
+    }
+    TestWidget.prototype.__render = jest.fn(TestWidget.prototype.__render);
+    TestWidget.prototype.__patch = jest.fn(TestWidget.prototype.__patch);
+
+    const widget = new TestWidget();
+    let prom = widget.mount(fixture);
+    widget.state.val = 2;
+    await prom;
+    expect(fixture.innerHTML).toBe("<div>2</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(1);
+
+    // unmount and re-mount, as in this case, willStart won't be called, so it's
+    // slightly different
+    widget.unmount();
+    prom = widget.mount(fixture);
+    widget.state.val = 3;
+    await prom;
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(3);
+    expect(TestWidget.prototype.__patch).toHaveBeenCalledTimes(2);
+    expect(steps).toEqual([2, 2, 3]);
+  });
 });
 
 describe("dynamic root nodes", () => {

tests/router/__snapshots__/route_component.test.ts.snap

@@ -35,7 +35,7 @@ exports[`RouteComponent can render simple cases 1`] = `
             let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
             let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
             const fiber = w3.__owl__.currentFiber;
-            def2.then(function () {if (fiber.isCancelled) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            def2.then(function () {if (fiber.isCompleted) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             utils.defineProxy(vn5, pvnode);
             w3.__owl__.pvnode = pvnode;
         }