[REL] v2.0.0-beta-17

# v2.0.0-beta-17

- imp: types: expose ComponentConstructor for typing purpose
- fix: compiler: fix falsy values for properties not keeping input empty
- fix: app: allow mounting owl apps in iframe

package.json

@@ -1,9 +1,8 @@
 {
   "name": "@odoo/owl",
-  "version": "2.0.0-beta-10",
+  "version": "2.0.0-beta-17",
   "description": "Odoo Web Library (OWL)",
   "main": "dist/owl.cjs.js",
-  "browser": "dist/owl.iife.js",
   "module": "dist/owl.es.js",
   "types": "dist/types/owl.d.ts",
   "files": [

rollup.config.js

@@ -6,6 +6,14 @@ import dts from "rollup-plugin-dts";
 
 let input, output;
 
+const IIFE_FILENAME = "dist/owl.iife.js";
+const CJS_FILENAME = "dist/owl.cjs.js";
+const ES_FILENAME = "dist/owl.es.js";
+
+if (pkg.module !== ES_FILENAME || pkg.main !== CJS_FILENAME) {
+  throw new Error("package.json has been modified. Build script should be updated accordingly");
+}  
+
 const outro = `
 __info__.version = '${pkg.version}';
 __info__.date = '${new Date().toISOString()}';
@@ -23,19 +31,19 @@ switch (process.argv[4]) {
   case "runtime":
     input = "src/runtime/index.ts";
     output = [
-      getConfigForFormat('esm', addSuffix(pkg.module,  'runtime'), outro),
-      getConfigForFormat('cjs', addSuffix(pkg.main,  'runtime'), outro),
-      getConfigForFormat('iife', addSuffix(pkg.browser,  'runtime'), outro),
-      getConfigForFormat('iife', addSuffix(pkg.browser,  'runtime'), outro, true),
+      getConfigForFormat('esm', addSuffix(ES_FILENAME,  'runtime'), outro),
+      getConfigForFormat('cjs', addSuffix(CJS_FILENAME,  'runtime'), outro),
+      getConfigForFormat('iife', addSuffix(IIFE_FILENAME,  'runtime'), outro),
+      getConfigForFormat('iife', addSuffix(IIFE_FILENAME,  'runtime'), outro, true),
     ]
     break;
   default:
     input = "src/index.ts",
     output = [
-      getConfigForFormat('esm', pkg.module, outro),
-      getConfigForFormat('cjs', pkg.main, outro),
-      getConfigForFormat('iife', pkg.browser, outro),
-      getConfigForFormat('iife', pkg.browser, outro, true),
+      getConfigForFormat('esm', ES_FILENAME, outro),
+      getConfigForFormat('cjs', CJS_FILENAME, outro),
+      getConfigForFormat('iife', IIFE_FILENAME, outro),
+      getConfigForFormat('iife', IIFE_FILENAME, outro, true),
     ]
   }
 

src/compiler/code_generator.ts

@@ -1,3 +1,4 @@
+import { isProp } from "../runtime/blockdom/attributes";
 import {
   compileExpr,
   compileExprToArray,
@@ -22,13 +23,14 @@ import {
   ASTTif,
   ASTTKey,
   ASTTOut,
-  ASTTSet,
-  ASTTranslation,
-  ASTType,
   ASTTPortal,
-  EventHandlers,
+  ASTTranslation,
+  ASTTSet,
+  ASTType,
   Attrs,
+  EventHandlers,
 } from "./parser";
+import { OwlError } from "../runtime/error_handling";
 
 type BlockType = "block" | "text" | "multi" | "list" | "html" | "comment";
 
@@ -143,7 +145,7 @@ interface Context {
   ctxVar?: string;
 }
 
-function createContext(parentCtx: Context, params?: Partial<Context>) {
+function createContext(parentCtx: Context, params?: Partial<Context>): Context {
   return Object.assign(
     {
       block: null,
@@ -334,8 +336,8 @@ export class CodeGenerator {
     this.addLine(`const ${varName} = ${expr};`);
   }
 
-  insertAnchor(block: BlockDescription) {
-    const tag = `block-child-${block.children.length}`;
+  insertAnchor(block: BlockDescription, index: number = block.children.length) {
+    const tag = `block-child-${index}`;
     const anchor = xmlDoc.createElement(tag);
     block.insert(anchor);
   }
@@ -534,7 +536,7 @@ export class CodeGenerator {
       .slice(1)
       .map((m) => {
         if (!MODS.has(m)) {
-          throw new Error(`Unknown event modifier: '${m}'`);
+          throw new OwlError(`Unknown event modifier: '${m}'`);
         }
         return `"${m}"`;
       });
@@ -578,13 +580,22 @@ export class CodeGenerator {
         attrName = key.slice(7);
         attrs["block-attribute-" + idx] = attrName;
       } else if (key.startsWith("t-att")) {
+        attrName = key === "t-att" ? null : key.slice(6);
         expr = compileExpr(ast.attrs[key]);
+        if (attrName && isProp(ast.tag, attrName)) {
+          // we force a new string or new boolean to bypass the equality check in blockdom when patching same value
+          if (attrName === "value") {
+            // When the expression is falsy, fall back to an empty string
+            expr = `new String((${expr}) || "")`;
+          } else {
+            expr = `new Boolean(${expr})`;
+          }
+        }
         const idx = block!.insertData(expr, "attr");
         if (key === "t-att") {
           attrs[`block-attributes`] = String(idx);
         } else {
-          attrName = key.slice(6);
-          attrs[`block-attribute-${idx}`] = attrName;
+          attrs[`block-attribute-${idx}`] = attrName!;
         }
       } else if (this.translatableAttributes.includes(key)) {
         attrs[key] = this.translateFn(ast.attrs[key]);
@@ -692,7 +703,7 @@ export class CodeGenerator {
       const children = ast.content;
       for (let i = 0; i < children.length; i++) {
         const child = ast.content[i];
-        const subCtx: Context = createContext(ctx, {
+        const subCtx = createContext(ctx, {
           block,
           index: block!.childNumber,
           forceNewBlock: false,
@@ -754,21 +765,37 @@ export class CodeGenerator {
       this.insertAnchor(block);
     }
     block = this.createBlock(block, "html", ctx);
-    this.helpers.add(ast.expr === "0" ? "zero" : "safeOutput");
-    let expr = ast.expr === "0" ? "ctx[zero]" : `safeOutput(${compileExpr(ast.expr)})`;
-    if (ast.body) {
-      const nextId = BlockDescription.nextBlockId;
-      const subCtx: Context = createContext(ctx);
+    let blockStr;
+    if (ast.expr === "0") {
+      this.helpers.add("zero");
+      blockStr = `ctx[zero]`;
+    } else if (ast.body) {
+      let bodyValue = null;
+      bodyValue = BlockDescription.nextBlockId;
+      const subCtx = createContext(ctx);
       this.compileAST({ type: ASTType.Multi, content: ast.body }, subCtx);
-      this.helpers.add("withDefault");
-      expr = `withDefault(${expr}, b${nextId})`;
+      this.helpers.add("safeOutput");
+      blockStr = `safeOutput(${compileExpr(ast.expr)}, b${bodyValue})`;
+    } else {
+      this.helpers.add("safeOutput");
+      blockStr = `safeOutput(${compileExpr(ast.expr)})`;
     }
-    this.insertBlock(`${expr}`, block, ctx);
+    this.insertBlock(blockStr, block, ctx);
+  }
+
+  compileTIfBranch(content: AST, block: BlockDescription, ctx: Context) {
+    this.target.indentLevel++;
+    let childN = block.children.length;
+    this.compileAST(content, createContext(ctx, { block, index: ctx.index }));
+    if (block.children.length > childN) {
+      // we have some content => need to insert an anchor at correct index
+      this.insertAnchor(block!, childN);
+    }
+    this.target.indentLevel--;
   }
 
   compileTIf(ast: ASTTif, ctx: Context, nextNode?: ASTDomNode) {
-    let { block, forceNewBlock, index } = ctx;
-    let currentIndex = index;
+    let { block, forceNewBlock } = ctx;
     const codeIdx = this.target.code.length;
     const isNewBlock = !block || (block.type !== "multi" && forceNewBlock);
     if (block) {
@@ -778,28 +805,16 @@ export class CodeGenerator {
       block = this.createBlock(block, "multi", ctx);
     }
     this.addLine(`if (${compileExpr(ast.condition)}) {`);
-    this.target.indentLevel++;
-    this.insertAnchor(block!);
-    const subCtx: Context = createContext(ctx, { block, index: currentIndex });
-    this.compileAST(ast.content, subCtx);
-    this.target.indentLevel--;
+    this.compileTIfBranch(ast.content, block, ctx);
     if (ast.tElif) {
       for (let clause of ast.tElif) {
         this.addLine(`} else if (${compileExpr(clause.condition)}) {`);
-        this.target.indentLevel++;
-        this.insertAnchor(block);
-        const subCtx: Context = createContext(ctx, { block, index: currentIndex });
-        this.compileAST(clause.content, subCtx);
-        this.target.indentLevel--;
+        this.compileTIfBranch(clause.content, block, ctx);
       }
     }
     if (ast.tElse) {
       this.addLine(`} else {`);
-      this.target.indentLevel++;
-      this.insertAnchor(block);
-      const subCtx: Context = createContext(ctx, { block, index: currentIndex });
-      this.compileAST(ast.tElse, subCtx);
-      this.target.indentLevel--;
+      this.compileTIfBranch(ast.tElse, block, ctx);
     }
     this.addLine("}");
     if (isNewBlock) {
@@ -861,8 +876,9 @@ export class CodeGenerator {
     this.define(`key${this.target.loopLevel}`, ast.key ? compileExpr(ast.key) : loopVar);
     if (this.dev) {
       // Throw error on duplicate keys in dev mode
+      this.helpers.add("OwlError");
       this.addLine(
-        `if (keys${block.id}.has(key${this.target.loopLevel})) { throw new Error(\`Got duplicate key in t-foreach: \${key${this.target.loopLevel}}\`)}`
+        `if (keys${block.id}.has(key${this.target.loopLevel})) { throw new OwlError(\`Got duplicate key in t-foreach: \${key${this.target.loopLevel}}\`)}`
       );
       this.addLine(`keys${block.id}.add(key${this.target.loopLevel});`);
     }
@@ -885,7 +901,7 @@ export class CodeGenerator {
       this.addLine("}");
     }
 
-    const subCtx: Context = createContext(ctx, { block, index: loopVar });
+    const subCtx = createContext(ctx, { block, index: loopVar });
     this.compileAST(ast.body, subCtx);
     if (ast.memo) {
       this.addLine(
@@ -932,7 +948,7 @@ export class CodeGenerator {
     for (let i = 0, l = ast.content.length; i < l; i++) {
       const child = ast.content[i];
       const isTSet = child.type === ASTType.TSet;
-      const subCtx: Context = createContext(ctx, {
+      const subCtx = createContext(ctx, {
         block,
         index,
         forceNewBlock: !isTSet,
@@ -978,7 +994,7 @@ export class CodeGenerator {
       this.addLine(`${ctxVar}[isBoundary] = 1;`);
       this.helpers.add("isBoundary");
       const nextId = BlockDescription.nextBlockId;
-      const subCtx: Context = createContext(ctx, { preventRoot: true, ctxVar });
+      const subCtx = createContext(ctx, { preventRoot: true, ctxVar });
       this.compileAST({ type: ASTType.Multi, content: ast.body }, subCtx);
       if (nextId !== BlockDescription.nextBlockId) {
         this.helpers.add("zero");
@@ -1084,7 +1100,7 @@ export class CodeGenerator {
         name = _name;
         value = `bind(ctx, ${value || undefined})`;
       } else {
-        throw new Error("Invalid prop suffix");
+        throw new OwlError("Invalid prop suffix");
       }
     }
     name = /^[a-z_]+$/i.test(name) ? name : `'${name}'`;

src/compiler/inline_expressions.ts

@@ -1,3 +1,5 @@
+import { OwlError } from "../runtime/error_handling";
+
 /**
  * Owl QWeb Expression Parser
  *
@@ -106,14 +108,14 @@ let tokenizeString: Tokenizer = function (expr) {
       i++;
       cur = expr[i];
       if (!cur) {
-        throw new Error("Invalid expression");
+        throw new OwlError("Invalid expression");
       }
       s += cur;
     }
     i++;
   }
   if (expr[i] !== start) {
-    throw new Error("Invalid expression");
+    throw new OwlError("Invalid expression");
   }
   s += start;
   if (start === "`") {
@@ -223,7 +225,7 @@ export function tokenize(expr: string): Token[] {
     error = e; // Silence all errors and throw a generic error below
   }
   if (current.length || error) {
-    throw new Error(`Tokenizer error: could not tokenize \`${expr}\``);
+    throw new OwlError(`Tokenizer error: could not tokenize \`${expr}\``);
   }
   return result;
 }

src/compiler/parser.ts

@@ -1,3 +1,5 @@
+import { OwlError } from "../runtime/error_handling";
+
 // -----------------------------------------------------------------------------
 // AST Type definition
 // -----------------------------------------------------------------------------
@@ -319,7 +321,7 @@ function parseDOMNode(node: Element, ctx: ParsingContext): AST | null {
     return null;
   }
   if (tagName.startsWith("block-")) {
-    throw new Error(`Invalid tag name: '${tagName}'`);
+    throw new OwlError(`Invalid tag name: '${tagName}'`);
   }
   ctx = Object.assign({}, ctx);
   if (tagName === "pre") {
@@ -340,13 +342,15 @@ function parseDOMNode(node: Element, ctx: ParsingContext): AST | null {
     const value = node.getAttribute(attr)!;
     if (attr.startsWith("t-on")) {
       if (attr === "t-on") {
-        throw new Error("Missing event name with t-on directive");
+        throw new OwlError("Missing event name with t-on directive");
       }
       on = on || {};
       on[attr.slice(5)] = value;
     } else if (attr.startsWith("t-model")) {
       if (!["input", "select", "textarea"].includes(tagName)) {
-        throw new Error("The t-model directive only works with <input>, <textarea> and <select>");
+        throw new OwlError(
+          "The t-model directive only works with <input>, <textarea> and <select>"
+        );
       }
 
       let baseExpr, expr;
@@ -359,7 +363,7 @@ function parseDOMNode(node: Element, ctx: ParsingContext): AST | null {
         baseExpr = value.slice(0, index);
         expr = value.slice(index + 1, -1);
       } else {
-        throw new Error(`Invalid t-model expression: "${value}" (it should be assignable)`);
+        throw new OwlError(`Invalid t-model expression: "${value}" (it should be assignable)`);
       }
 
       const typeAttr = node.getAttribute("type");
@@ -390,10 +394,10 @@ function parseDOMNode(node: Element, ctx: ParsingContext): AST | null {
         ctx.tModelInfo = model;
       }
     } else if (attr.startsWith("block-")) {
-      throw new Error(`Invalid attribute: '${attr}'`);
+      throw new OwlError(`Invalid attribute: '${attr}'`);
     } else if (attr !== "t-name") {
       if (attr.startsWith("t-") && !attr.startsWith("t-att")) {
-        throw new Error(`Unknown QWeb directive: '${attr}'`);
+        throw new OwlError(`Unknown QWeb directive: '${attr}'`);
       }
       const tModel = ctx.tModelInfo;
       if (tModel && ["t-att-value", "t-attf-value"].includes(attr)) {
@@ -447,7 +451,7 @@ function parseTEscNode(node: Element, ctx: ParsingContext): AST | null {
     };
   }
   if (ast.type === ASTType.TComponent) {
-    throw new Error("t-esc is not supported on Component nodes");
+    throw new OwlError("t-esc is not supported on Component nodes");
   }
   return tesc;
 }
@@ -503,7 +507,7 @@ function parseTForEach(node: Element, ctx: ParsingContext): AST | null {
   node.removeAttribute("t-as");
   const key = node.getAttribute("t-key");
   if (!key) {
-    throw new Error(
+    throw new OwlError(
       `"Directive t-foreach should always be used with a t-key!" (expression: t-foreach="${collection}" t-as="${elem}")`
     );
   }
@@ -686,7 +690,9 @@ function parseComponent(node: Element, ctx: ParsingContext): AST | null {
   let isDynamic = node.hasAttribute("t-component");
 
   if (isDynamic && name !== "t") {
-    throw new Error(`Directive 't-component' can only be used on <t> nodes (used on a <${name}>)`);
+    throw new OwlError(
+      `Directive 't-component' can only be used on <t> nodes (used on a <${name}>)`
+    );
   }
 
   if (!(firstLetter === firstLetter.toUpperCase() || isDynamic)) {
@@ -713,7 +719,7 @@ function parseComponent(node: Element, ctx: ParsingContext): AST | null {
         on[name.slice(5)] = value;
       } else {
         const message = directiveErrorMap.get(name.split("-").slice(0, 2).join("-"));
-        throw new Error(message || `unsupported directive on Component: ${name}`);
+        throw new OwlError(message || `unsupported directive on Component: ${name}`);
       }
     } else {
       props = props || {};
@@ -729,7 +735,7 @@ function parseComponent(node: Element, ctx: ParsingContext): AST | null {
     const slotNodes = Array.from(clone.querySelectorAll("[t-set-slot]"));
     for (let slotNode of slotNodes) {
       if (slotNode.tagName !== "t") {
-        throw new Error(
+        throw new OwlError(
           `Directive 't-set-slot' can only be used on <t> nodes (used on a <${slotNode.tagName}>)`
         );
       }
@@ -904,7 +910,7 @@ function normalizeTIf(el: Element) {
     let nattr = (name: string) => +!!node.getAttribute(name);
     if (prevElem && (pattr("t-if") || pattr("t-elif"))) {
       if (pattr("t-foreach")) {
-        throw new Error(
+        throw new OwlError(
           "t-if cannot stay at the same level as t-foreach when using t-elif or t-else"
         );
       }
@@ -913,19 +919,19 @@ function normalizeTIf(el: Element) {
           return a + b;
         }) > 1
       ) {
-        throw new Error("Only one conditional branching directive is allowed per node");
+        throw new OwlError("Only one conditional branching directive is allowed per node");
       }
       // All text (with only spaces) and comment nodes (nodeType 8) between
       // branch nodes are removed
       let textNode;
       while ((textNode = node.previousSibling) !== prevElem) {
         if (textNode!.nodeValue!.trim().length && textNode!.nodeType !== 8) {
-          throw new Error("text is not allowed between branching directives");
+          throw new OwlError("text is not allowed between branching directives");
         }
         textNode!.remove();
       }
     } else {
-      throw new Error(
+      throw new OwlError(
         "t-elif and t-else directives must be preceded by a t-if or t-elif directive"
       );
     }
@@ -946,7 +952,7 @@ function normalizeTEsc(el: Element) {
   );
   for (const el of elements) {
     if (el.childNodes.length) {
-      throw new Error("Cannot have t-esc on a component that already has content");
+      throw new OwlError("Cannot have t-esc on a component that already has content");
     }
     const value = el.getAttribute("t-esc");
     el.removeAttribute("t-esc");
@@ -1000,7 +1006,7 @@ function parseXML(xml: string): XMLDocument {
         }
       }
     }
-    throw new Error(msg);
+    throw new OwlError(msg);
   }
 
   return doc;

src/runtime/app.ts

@@ -1,9 +1,8 @@
 import { Component, ComponentConstructor, Props } from "./component";
 import { ComponentNode } from "./component_node";
-import { nodeErrorHandlers } from "./error_handling";
+import { nodeErrorHandlers, OwlError } from "./error_handling";
 import { Fiber, MountOptions } from "./fibers";
 import { Scheduler } from "./scheduler";
-import { STATUS } from "./status";
 import { validateProps } from "./template_helpers";
 import { TemplateSet, TemplateSetConfig } from "./template_set";
 import { validateTarget } from "./utils";
@@ -141,10 +140,7 @@ export class App<
     return (props: P, key: string, ctx: ComponentNode, parent: any, C: any) => {
       let children = ctx.children;
       let node: any = children[key];
-      if (
-        node &&
-        (node.status === STATUS.DESTROYED || (isDynamic && node.component.constructor !== C))
-      ) {
+      if (isDynamic && node && node.component.constructor !== C) {
         node = undefined;
       }
       const parentFiber = ctx.fiber!;
@@ -158,9 +154,9 @@ export class App<
         if (isStatic) {
           C = parent.constructor.components[name as any];
           if (!C) {
-            throw new Error(`Cannot find the definition of component "${name}"`);
+            throw new OwlError(`Cannot find the definition of component "${name}"`);
           } else if (!(C.prototype instanceof Component)) {
-            throw new Error(
+            throw new OwlError(
               `"${name}" is not a Component. It must inherit from the Component class`
             );
           }

src/runtime/blockdom/attributes.ts

@@ -144,7 +144,7 @@ export function updateClass(this: HTMLElement, val: any, oldVal: any) {
 export function makePropSetter(name: string): Setter<HTMLElement> {
   return function setProp(this: HTMLElement, value: any) {
     // support 0, fallback to empty string for other falsy values
-    (this as any)[name] = value === 0 ? 0 : value || "";
+    (this as any)[name] = value === 0 ? 0 : value ? value.valueOf() : "";
   };
 }
 

src/runtime/blockdom/block_compiler.ts

@@ -1,3 +1,4 @@
+import { OwlError } from "../error_handling";
 import {
   attrsSetter,
   attrsUpdater,
@@ -245,7 +246,7 @@ function buildTree(
       };
     }
   }
-  throw new Error("boom");
+  throw new OwlError("boom");
 }
 
 function addRef(tree: IntermediateTree) {

src/runtime/component_node.ts

@@ -1,7 +1,7 @@
 import type { App, Env } from "./app";
 import { BDom, VNode } from "./blockdom";
 import { Component, ComponentConstructor, Props } from "./component";
-import { fibersInError, handleError } from "./error_handling";
+import { fibersInError, handleError, OwlError } from "./error_handling";
 import { Fiber, makeChildFiber, makeRootFiber, MountFiber, MountOptions } from "./fibers";
 import {
   clearReactivesForCallback,
@@ -18,7 +18,7 @@ let currentNode: ComponentNode | null = null;
 
 export function getCurrent(): ComponentNode {
   if (!currentNode) {
-    throw new Error("No active component (a hook function should only be called in 'setup')");
+    throw new OwlError("No active component (a hook function should only be called in 'setup')");
   }
   return currentNode;
 }
@@ -83,7 +83,6 @@ export class ComponentNode<P extends Props = any, E = any> implements VNode<Comp
 
   renderFn: Function;
   parent: ComponentNode | null;
-  level: number;
   childEnv: Env;
   children: { [key: string]: ComponentNode } = Object.create(null);
   refs: any = {};
@@ -108,7 +107,6 @@ export class ComponentNode<P extends Props = any, E = any> implements VNode<Comp
     this.parent = parent;
     this.props = props;
     this.parentKey = parentKey;
-    this.level = parent ? parent.level + 1 : 0;
     const defaultProps = C.defaultProps;
     props = Object.assign({}, props);
     if (defaultProps) {

src/runtime/error_handling.ts

@@ -1,6 +1,11 @@
 import type { ComponentNode } from "./component_node";
 import type { Fiber } from "./fibers";
 
+// Custom error class that wraps error that happen in the owl lifecycle
+export class OwlError extends Error {
+  cause?: any;
+}
+
 // Maps fibers to thrown errors
 export const fibersInError: WeakMap<Fiber, any> = new WeakMap();
 export const nodeErrorHandlers: WeakMap<ComponentNode, ((error: any) => void)[]> = new WeakMap();
@@ -37,7 +42,14 @@ function _handleError(node: ComponentNode | null, error: any): boolean {
 
 type ErrorParams = { error: any } & ({ node: ComponentNode } | { fiber: Fiber });
 export function handleError(params: ErrorParams) {
-  const error = params.error;
+  let { error } = params;
+  // Wrap error if it wasn't wrapped by wrapError (ie when not in dev mode)
+  if (!(error instanceof OwlError)) {
+    error = Object.assign(
+      new OwlError(`An error occured in the owl lifecycle (see this Error's "cause" property)`),
+      { cause: error }
+    );
+  }
   const node = "node" in params ? params.node : params.fiber.node;
   const fiber = "fiber" in params ? params.fiber : node.fiber!;
 

src/runtime/event_handling.ts

@@ -1,5 +1,6 @@
 import { filterOutModifiersFromData } from "./blockdom/config";
 import { STATUS } from "./status";
+import { OwlError } from "./error_handling";
 
 export const mainEventHandler = (data: any, ev: Event, currentTarget?: EventTarget | null) => {
   const { data: _data, modifiers } = filterOutModifiersFromData(data);
@@ -33,7 +34,7 @@ export const mainEventHandler = (data: any, ev: Event, currentTarget?: EventTarg
   if (Object.hasOwnProperty.call(data, 0)) {
     const handler = data[0];
     if (typeof handler !== "function") {
-      throw new Error(`Invalid handler (expected a function, received: '${handler}')`);
+      throw new OwlError(`Invalid handler (expected a function, received: '${handler}')`);
     }
     let node = data[1] ? data[1].__owl__ : null;
     if (node ? node.status === STATUS.MOUNTED : true) {

src/runtime/fibers.ts

@@ -1,6 +1,6 @@
 import { BDom, mount } from "./blockdom";
 import type { ComponentNode } from "./component_node";
-import { fibersInError, handleError } from "./error_handling";
+import { fibersInError, handleError, OwlError } from "./error_handling";
 import { STATUS } from "./status";
 
 export function makeChildFiber(node: ComponentNode, parent: Fiber): Fiber {
@@ -43,7 +43,7 @@ export function makeRootFiber(node: ComponentNode): Fiber {
 }
 
 function throwOnRender() {
-  throw new Error("Attempted to render cancelled fiber");
+  throw new OwlError("Attempted to render cancelled fiber");
 }
 
 /**
@@ -56,6 +56,7 @@ function cancelFibers(fibers: Fiber[]): number {
     fiber.render = throwOnRender;
     if (node.status === STATUS.NEW) {
       node.destroy();
+      delete node.parent!.children[node.parentKey!];
     }
     node.fiber = null;
     if (fiber.bdom) {

src/runtime/index.ts

@@ -36,6 +36,7 @@ export const blockDom = {
 export { App, mount } from "./app";
 export { xml } from "./template_set";
 export { Component } from "./component";
+export type { ComponentConstructor } from "./component";
 export { useComponent, useState } from "./component_node";
 export { status } from "./status";
 export { reactive, markRaw, toRaw } from "./reactivity";
@@ -54,5 +55,6 @@ export {
   onError,
 } from "./lifecycle_hooks";
 export { validate } from "./validation";
+export { OwlError } from "./error_handling";
 
 export const __info__ = {};

src/runtime/lifecycle_hooks.ts

@@ -1,21 +1,30 @@
 import { getCurrent } from "./component_node";
-import { nodeErrorHandlers } from "./error_handling";
+import { nodeErrorHandlers, OwlError } from "./error_handling";
 
 const TIMEOUT = Symbol("timeout");
 function wrapError(fn: (...args: any[]) => any, hookName: string) {
-  const error = new Error(`The following error occurred in ${hookName}: `) as Error & {
+  const error = new OwlError(`The following error occurred in ${hookName}: `) as Error & {
     cause: any;
   };
-  const timeoutError = new Error(`${hookName}'s promise hasn't resolved after 3 seconds`);
+  const timeoutError = new OwlError(`${hookName}'s promise hasn't resolved after 3 seconds`);
   const node = getCurrent();
   return (...args: any[]) => {
+    const onError = (cause: any) => {
+      error.cause = cause;
+      if (cause instanceof Error) {
+        error.message += `"${cause.message}"`;
+      } else {
+        error.message = `Something that is not an Error was thrown in ${hookName} (see this Error's "cause" property)`;
+      }
+      throw error;
+    };
     try {
       const result = fn(...args);
       if (result instanceof Promise) {
         if (hookName === "onWillStart" || hookName === "onWillUpdateProps") {
           const fiber = node.fiber;
           Promise.race([
-            result,
+            result.catch(() => {}),
             new Promise((resolve) => setTimeout(() => resolve(TIMEOUT), 3000)),
           ]).then((res) => {
             if (res === TIMEOUT && node.fiber === fiber) {
@@ -23,20 +32,11 @@ function wrapError(fn: (...args: any[]) => any, hookName: string) {
             }
           });
         }
-        return result.catch((cause) => {
-          error.cause = cause;
-          if (cause instanceof Error) {
-            error.message += `"${cause.message}"`;
-          }
-          throw error;
-        });
+        return result.catch(onError);
       }
       return result;
     } catch (cause) {
-      if (cause instanceof Error) {
-        error.message += `"${cause.message}"`;
-      }
-      throw error;
+      onError(cause);
     }
   };
 }

src/runtime/portal.ts

@@ -1,6 +1,7 @@
 import { onWillUnmount } from "./lifecycle_hooks";
 import { BDom, text, VNode } from "./blockdom";
 import { Component } from "./component";
+import { OwlError } from "./error_handling";
 
 const VText: any = text("").constructor;
 
@@ -24,7 +25,7 @@ class VPortal extends VText implements Partial<VNode<VPortal>> {
       }
       this.target = el && el.querySelector(this.selector);
       if (!this.target) {
-        throw new Error("invalid portal target");
+        throw new OwlError("invalid portal target");
       }
     }
     this.realBDom!.mount(this.target!, null);

src/runtime/reactivity.ts

@@ -1,4 +1,5 @@
 import { Callback } from "./utils";
+import { OwlError } from "./error_handling";
 
 // Allows to get the target of a Reactive (used for making a new Reactive from the underlying object)
 export const TARGET = Symbol("Target");
@@ -197,7 +198,7 @@ export function reactive<T extends Target>(
   callback: Callback = () => {}
 ): Reactive<T> | NonReactive<T> {
   if (!canBeMadeReactive(target)) {
-    throw new Error(`Cannot make the given value reactive`);
+    throw new OwlError(`Cannot make the given value reactive`);
   }
   if (SKIP in target) {
     return target as NonReactive<T>;

src/runtime/template_helpers.ts

@@ -4,6 +4,7 @@ import { html } from "./blockdom/index";
 import { isOptional, validateSchema } from "./validation";
 import type { ComponentConstructor } from "./component";
 import { markRaw } from "./reactivity";
+import { OwlError } from "./error_handling";
 
 const ObjectCreate = Object.create;
 /**
@@ -70,7 +71,7 @@ function prepareList(collection: any): [any[], any[], number, any[]] {
     values = Object.keys(collection);
     keys = Object.values(collection);
   } else {
-    throw new Error("Invalid loop expression");
+    throw new OwlError("Invalid loop expression");
   }
   const n = values.length;
   return [keys, values, n, new Array(n)];
@@ -129,9 +130,9 @@ class LazyValue {
 /*
  * Safely outputs `value` as a block depending on the nature of `value`
  */
-export function safeOutput(value: any): ReturnType<typeof toggler> {
-  if (!value) {
-    return value;
+export function safeOutput(value: any, defaultValue?: any): ReturnType<typeof toggler> {
+  if (value === undefined) {
+    return defaultValue ? toggler("default", defaultValue) : toggler("undefined", text(""));
   }
   let safeKey;
   let block;
@@ -191,7 +192,7 @@ function multiRefSetter(refs: RefMap, name: string): RefSetter {
     if (el) {
       count++;
       if (count > 1) {
-        throw new Error("Cannot have 2 elements with same ref name at the same time");
+        throw new OwlError("Cannot have 2 elements with same ref name at the same time");
       }
     }
     if (count === 0 || el) {
@@ -233,7 +234,7 @@ export function validateProps<P>(name: string | ComponentConstructor<P>, props:
         : name in schema && !("*" in schema) && !isOptional(schema[name]);
     for (let p in defaultProps) {
       if (isMandatory(p)) {
-        throw new Error(
+        throw new OwlError(
           `A default value cannot be defined for a mandatory prop (name: '${p}', component: ${ComponentClass.name})`
         );
       }
@@ -242,7 +243,9 @@ export function validateProps<P>(name: string | ComponentConstructor<P>, props:
 
   const errors = validateSchema(props, schema);
   if (errors.length) {
-    throw new Error(`Invalid props for component '${ComponentClass.name}': ` + errors.join(", "));
+    throw new OwlError(
+      `Invalid props for component '${ComponentClass.name}': ` + errors.join(", ")
+    );
   }
 }
 
@@ -264,4 +267,5 @@ export const helpers = {
   bind,
   createCatcher,
   markRaw,
+  OwlError,
 };

src/runtime/template_set.ts

@@ -3,6 +3,7 @@ import { comment, createBlock, html, list, multi, text, toggler } from "./blockd
 import { getCurrent } from "./component_node";
 import { Portal, portalTemplate } from "./portal";
 import { helpers } from "./template_helpers";
+import { OwlError } from "./error_handling";
 
 const bdom = { text, createBlock, list, multi, html, toggler, comment };
 
@@ -31,7 +32,7 @@ function parseXML(xml: string): Document {
         }
       }
     }
-    throw new Error(msg);
+    throw new OwlError(msg);
   }
   return doc;
 }
@@ -76,7 +77,7 @@ export class TemplateSet {
       if (currentAsString === newAsString) {
         return;
       }
-      throw new Error(`Template ${name} already defined with different content`);
+      throw new OwlError(`Template ${name} already defined with different content`);
     }
     this.rawTemplates[name] = template;
   }
@@ -102,7 +103,7 @@ export class TemplateSet {
           const componentName = getCurrent().component.constructor.name;
           extraInfo = ` (for component "${componentName}")`;
         } catch {}
-        throw new Error(`Missing template: "${name}"${extraInfo}`);
+        throw new OwlError(`Missing template: "${name}"${extraInfo}`);
       }
       const isFn = typeof rawTemplate === "function" && !(rawTemplate instanceof Element);
       const templateFn = isFn ? rawTemplate : this._compileTemplate(name, rawTemplate);
@@ -119,7 +120,7 @@ export class TemplateSet {
   }
 
   _compileTemplate(name: string, template: string | Element): ReturnType<typeof compile> {
-    throw new Error(`Unable to compile a template. Please use owl full build instead`);
+    throw new OwlError(`Unable to compile a template. Please use owl full build instead`);
   }
 
   callTemplate(owner: any, subTemplate: string, ctx: any, parent: any, key: any): any {

src/runtime/utils.ts

@@ -1,3 +1,4 @@
+import { OwlError } from "./error_handling";
 export type Callback = () => void;
 
 /**
@@ -27,12 +28,18 @@ export function batched(callback: Callback): Callback {
 }
 
 export function validateTarget(target: HTMLElement) {
-  if (!(target instanceof HTMLElement)) {
-    throw new Error("Cannot mount component: the target is not a valid DOM element");
-  }
-  if (!document.body.contains(target)) {
-    throw new Error("Cannot mount a component on a detached dom node");
+  // Get the document and HTMLElement corresponding to the target to allow mounting in iframes
+  const document = target && target.ownerDocument;
+  if (document) {
+    const HTMLElement = document.defaultView!.HTMLElement;
+    if (target instanceof HTMLElement) {
+      if (!document.body.contains(target)) {
+        throw new OwlError("Cannot mount a component on a detached dom node");
+      }
+      return;
+    }
   }
+  throw new OwlError("Cannot mount component: the target is not a valid DOM element");
 }
 
 export class EventBus extends EventTarget {
@@ -54,7 +61,7 @@ export function whenReady(fn?: any): Promise<void> {
 export async function loadFile(url: string): Promise<string> {
   const result = await fetch(url);
   if (!result.ok) {
-    throw new Error("Error while fetching xml templates");
+    throw new OwlError("Error while fetching xml templates");
   }
   return await result.text();
 }

src/runtime/validation.ts

@@ -1,3 +1,5 @@
+import { OwlError } from "./error_handling";
+
 type BaseType =
   | typeof String
   | typeof Boolean
@@ -70,7 +72,7 @@ function toSchema(spec: SimplifiedSchema): NormalizedSchema {
 export function validate(obj: { [key: string]: any }, spec: Schema) {
   let errors = validateSchema(obj, spec);
   if (errors.length) {
-    throw new Error("Invalid object: " + errors.join(", "));
+    throw new OwlError("Invalid object: " + errors.join(", "));
   }
 }
 

tests/app/__snapshots__/app.test.ts.snap

@@ -29,6 +29,19 @@ exports[`app can configure an app with props 1`] = `
 }"
 `;
 
+exports[`app can mount app in an iframe 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  let block1 = createBlock(\`<div class=\\"my-div\\"/>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    return block1();
+  }
+}"
+`;
+
 exports[`app destroy remove the widget from the DOM 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

tests/app/app.test.ts

@@ -76,4 +76,22 @@ describe("app", () => {
       "Component 'Root' does not have a static props description"
     );
   });
+
+  test("can mount app in an iframe", async () => {
+    class SomeComponent extends Component {
+      static template = xml`<div class="my-div"/>`;
+    }
+
+    const iframe = document.createElement("iframe");
+    fixture.appendChild(iframe);
+    const app = new App(SomeComponent);
+    const iframeDoc = iframe.contentDocument!;
+    const comp = await app.mount(iframeDoc.body);
+    const div = iframeDoc.querySelector(".my-div");
+    expect(div).not.toBe(null);
+    expect(iframeDoc.contains(div)).toBe(true);
+    app.destroy();
+    expect(iframeDoc.contains(div)).toBe(false);
+    expect(status(comp)).toBe("destroyed");
+  });
 });

tests/compiler/__snapshots__/attributes.test.ts.snap

@@ -708,6 +708,20 @@ exports[`attributes updating classes (with obj notation) 1`] = `
 }"
 `;
 
+exports[`attributes updating property with falsy value 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  let block1 = createBlock(\`<input block-attribute-0=\\"value\\"/>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let attr1 = new String((ctx['v']) || \\"\\");
+    return block1([attr1]);
+  }
+}"
+`;
+
 exports[`attributes various escapes 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
@@ -745,7 +759,7 @@ exports[`special cases for some specific html attributes/properties input of typ
   let block1 = createBlock(\`<input type=\\"checkbox\\" block-attribute-0=\\"indeterminate\\"/>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let attr1 = ctx['v'];
+    let attr1 = new Boolean(ctx['v']);
     return block1([attr1]);
   }
 }"
@@ -759,7 +773,21 @@ exports[`special cases for some specific html attributes/properties input type=
   let block1 = createBlock(\`<input type=\\"checkbox\\" block-attribute-0=\\"checked\\"/>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let attr1 = ctx['flag'];
+    let attr1 = new Boolean(ctx['flag']);
+    return block1([attr1]);
+  }
+}"
+`;
+
+exports[`special cases for some specific html attributes/properties input with t-att-value (patching with same value 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  let block1 = createBlock(\`<input block-attribute-0=\\"value\\"/>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let attr1 = new String((ctx['v']) || \\"\\");
     return block1([attr1]);
   }
 }"
@@ -773,7 +801,21 @@ exports[`special cases for some specific html attributes/properties input with t
   let block1 = createBlock(\`<input block-attribute-0=\\"value\\"/>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let attr1 = ctx['v'];
+    let attr1 = new String((ctx['v']) || \\"\\");
+    return block1([attr1]);
+  }
+}"
+`;
+
+exports[`special cases for some specific html attributes/properties input, type checkbox, with t-att-checked (patching with same value 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  let block1 = createBlock(\`<input type=\\"checkbox\\" block-attribute-0=\\"checked\\"/>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let attr1 = new Boolean(ctx['v']);
     return block1([attr1]);
   }
 }"
@@ -787,7 +829,7 @@ exports[`special cases for some specific html attributes/properties select with
   let block1 = createBlock(\`<select block-attribute-0=\\"value\\"><option value=\\"potato\\">Potato</option><option value=\\"tomato\\">Tomato</option><option value=\\"onion\\">Onion</option></select>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let attr1 = ctx['value'];
+    let attr1 = new String((ctx['value']) || \\"\\");
     return block1([attr1]);
   }
 }"
@@ -801,7 +843,7 @@ exports[`special cases for some specific html attributes/properties textarea wit
   let block1 = createBlock(\`<textarea block-attribute-0=\\"value\\"/>\`);
   
   return function template(ctx, node, key = \\"\\") {
-    let attr1 = ctx['v'];
+    let attr1 = new String((ctx['v']) || \\"\\");
     return block1([attr1]);
   }
 }"

tests/compiler/__snapshots__/misc.test.ts.snap

@@ -166,13 +166,13 @@ exports[`misc global 4`] = `
 "function anonymous(app, bdom, helpers
 ) {
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
-  let { safeOutput, withDefault } = helpers;
+  let { safeOutput } = helpers;
   
   let block1 = createBlock(\`<div><block-child-0/></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
     const b3 = text(\`toto default\`);
-    const b2 = withDefault(safeOutput(ctx['toto']), b3);
+    const b2 = safeOutput(ctx['toto'], b3);
     return block1([], [b2]);
   }
 }"
@@ -269,7 +269,7 @@ exports[`misc other complex template 1`] = `
         ctx[\`category\`] = v_block15[i1];
         const key1 = ctx['category'].id;
         let attr6 = ctx['category'].id;
-        let attr7 = ctx['category'].id==ctx['options'].active_category_id;
+        let attr7 = new Boolean(ctx['category'].id==ctx['options'].active_category_id);
         let txt5 = ctx['category'].name;
         c_block15[i1] = withKey(block16([attr6, attr7, txt5]), key1);
       }
@@ -277,7 +277,7 @@ exports[`misc other complex template 1`] = `
       const b15 = list(c_block15);
       b14 = block14([], [b15]);
     }
-    let attr8 = ctx['search'].value;
+    let attr8 = new String((ctx['search'].value) || \\"\\");
     let hdlr4 = [ctx['updateFilter'], ctx];
     let hdlr5 = [ctx['updateFilter'], ctx];
     let hdlr6 = [ctx['clearSearch'], ctx];
@@ -291,7 +291,7 @@ exports[`misc other complex template 1`] = `
         if (!ctx['trigger'].manual&&ctx['trigger'].project_id===ctx['project'].id&&ctx['trigger'].category_id===ctx['options'].active_category_id) {
           let attr9 = \`trigger_\${ctx['trigger'].id}\`;
           let attr10 = \`trigger_\${ctx['trigger'].id}\`;
-          let attr11 = ctx['options'].trigger_display[ctx['trigger'].id];
+          let attr11 = new Boolean(ctx['options'].trigger_display[ctx['trigger'].id]);
           let attr12 = ctx['trigger'].id;
           let hdlr7 = [ctx['updateTriggerDisplay'], ctx];
           let attr13 = \`trigger_\${ctx['trigger'].id}\`;

tests/compiler/__snapshots__/t_esc.test.ts.snap

@@ -133,6 +133,31 @@ exports[`t-esc t-esc is escaped 1`] = `
 }"
 `;
 
+exports[`t-esc t-esc with the 0 number 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['var']);
+  }
+}"
+`;
+
+exports[`t-esc t-esc with the 0 number, in a p 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  let block1 = createBlock(\`<p><block-text-0/></p>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let txt1 = ctx['var'];
+    return block1([txt1]);
+  }
+}"
+`;
+
 exports[`t-esc t-esc work with spread operator 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
@@ -183,6 +208,17 @@ exports[`t-esc t-esc=0 is escaped 2`] = `
 }"
 `;
 
+exports[`t-esc top level t-esc with undefined 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['var']);
+  }
+}"
+`;
+
 exports[`t-esc variable 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

tests/compiler/__snapshots__/t_out.test.ts.snap

@@ -217,13 +217,13 @@ exports[`t-out t-out on a node with a body, as a default 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
-  let { safeOutput, withDefault } = helpers;
+  let { safeOutput } = helpers;
   
   let block1 = createBlock(\`<span><block-child-0/></span>\`);
   
   return function template(ctx, node, key = \\"\\") {
     const b3 = text(\`nope\`);
-    const b2 = withDefault(safeOutput(ctx['var']), b3);
+    const b2 = safeOutput(ctx['var'], b3);
     return block1([], [b2]);
   }
 }"
@@ -233,14 +233,14 @@ exports[`t-out t-out on a node with a dom node in body, as a default 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
-  let { safeOutput, withDefault } = helpers;
+  let { safeOutput } = helpers;
   
   let block1 = createBlock(\`<span><block-child-0/></span>\`);
   let block3 = createBlock(\`<div>nope</div>\`);
   
   return function template(ctx, node, key = \\"\\") {
     const b3 = block3();
-    const b2 = withDefault(safeOutput(ctx['var']), b3);
+    const b2 = safeOutput(ctx['var'], b3);
     return block1([], [b2]);
   }
 }"
@@ -407,6 +407,45 @@ exports[`t-out t-out with just a t-set t-value in body 1`] = `
 }"
 `;
 
+exports[`t-out t-out with the 0 number 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { safeOutput } = helpers;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return safeOutput(ctx['var']);
+  }
+}"
+`;
+
+exports[`t-out t-out with the 0 number, in a p 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { safeOutput } = helpers;
+  
+  let block1 = createBlock(\`<p><block-child-0/></p>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    const b2 = safeOutput(ctx['var']);
+    return block1([], [b2]);
+  }
+}"
+`;
+
+exports[`t-out top level t-out with undefined 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { safeOutput } = helpers;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return safeOutput(ctx['var']);
+  }
+}"
+`;
+
 exports[`t-out variable 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

tests/compiler/__snapshots__/t_set.test.ts.snap

@@ -534,13 +534,36 @@ exports[`t-set t-set with t-value (truthy) and body 1`] = `
 }"
 `;
 
+exports[`t-set t-set, multiple t-ifs, and a specific configuration 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { isBoundary, withDefault, setContextValue } = helpers;
+  
+  let block1 = createBlock(\`<p><div><span>First div</span></div><div><block-child-0/></div></p>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    ctx = Object.create(ctx);
+    ctx[isBoundary] = 1
+    let b2;
+    if (ctx['flag']) {
+      setContextValue(ctx, \\"bouh\\", 2);
+    }
+    if (!ctx['flag']) {
+      b2 = text(\`Second\`);
+    }
+    return block1([], [b2]);
+  }
+}"
+`;
+
 exports[`t-set t-set, t-if, and mix of expression/body lookup, 1 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
   let { isBoundary, withDefault, setContextValue } = helpers;
   
-  let block1 = createBlock(\`<div><block-child-0/><block-child-0/><block-text-0/></div>\`);
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
     ctx = Object.create(ctx);
@@ -562,7 +585,7 @@ exports[`t-set t-set, t-if, and mix of expression/body lookup, 2 1`] = `
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
   let { isBoundary, withDefault, setContextValue } = helpers;
   
-  let block1 = createBlock(\`<div><block-child-0/><block-child-0/><block-text-0/></div>\`);
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
     ctx = Object.create(ctx);

tests/compiler/attributes.test.ts

@@ -329,6 +329,35 @@ describe("attributes", () => {
     expect(fixture.innerHTML).toBe('<div value=""></div>');
   });
 
+  test("updating property with falsy value", async () => {
+    // render input with initial value
+    const template = `<input t-att-value="v"></input>`;
+    const bnode1 = renderToBdom(template, { v: false });
+    const fixture = makeTestFixture();
+    mount(bnode1, fixture);
+
+    const input = fixture.querySelector("input")!;
+    expect(input.value).toBe("");
+
+    patch(bnode1, renderToBdom(template, { v: "owl" }));
+    expect(input.value).toBe("owl");
+
+    patch(bnode1, renderToBdom(template, { v: false }));
+    expect(input.value).toBe("");
+
+    patch(bnode1, renderToBdom(template, { v: "owl" }));
+    expect(input.value).toBe("owl");
+
+    patch(bnode1, renderToBdom(template, { v: undefined }));
+    expect(input.value).toBe("");
+
+    patch(bnode1, renderToBdom(template, { v: "owl" }));
+    expect(input.value).toBe("owl");
+
+    patch(bnode1, renderToBdom(template, { v: null }));
+    expect(input.value).toBe("");
+  });
+
   test("changing a class with t-att-class", () => {
     // render input with initial value
     const template = `<div t-att-class="v"/>`;
@@ -429,6 +458,42 @@ describe("special cases for some specific html attributes/properties", () => {
     expect(input.value).toBe("potato");
   });
 
+  test("input with t-att-value (patching with same value", () => {
+    // render input with initial value
+    const template = `<input t-att-value="v"/>`;
+    const bnode1 = renderToBdom(template, { v: "zucchini" });
+    const fixture = makeTestFixture();
+    mount(bnode1, fixture);
+    const input = fixture.querySelector("input")!;
+    expect(input.value).toBe("zucchini");
+
+    // change value manually in input, to simulate user input
+    input.value = "tomato";
+    expect(input.value).toBe("tomato");
+
+    const bnode2 = renderToBdom(template, { v: "zucchini" });
+    patch(bnode1, bnode2);
+    expect(input.value).toBe("zucchini");
+  });
+
+  test("input, type checkbox, with t-att-checked (patching with same value", () => {
+    // render input with initial value
+    const template = `<input type="checkbox" t-att-checked="v"/>`;
+    const bnode1 = renderToBdom(template, { v: true });
+    const fixture = makeTestFixture();
+    mount(bnode1, fixture);
+    const input = fixture.querySelector("input")!;
+    expect(input.checked).toBe(true);
+
+    // change checked manually in input, to simulate user input
+    input.checked = false;
+    expect(input.checked).toBe(false);
+
+    const bnode2 = renderToBdom(template, { v: true });
+    patch(bnode1, bnode2);
+    expect(input.checked).toBe(true);
+  });
+
   test("input of type checkbox with t-att-indeterminate", () => {
     const template = `<input type="checkbox" t-att-indeterminate="v"/>`;
     const bnode1 = renderToBdom(template, { v: true });

tests/compiler/t_esc.test.ts

@@ -67,6 +67,21 @@ describe("t-esc", () => {
     );
   });
 
+  test("t-esc with the 0 number", () => {
+    const template = `<t t-esc="var"/>`;
+    expect(renderToString(template, { var: 0 })).toBe("0");
+  });
+
+  test("t-esc with the 0 number, in a p", () => {
+    const template = `<p><t t-esc="var"/></p>`;
+    expect(renderToString(template, { var: 0 })).toBe("<p>0</p>");
+  });
+
+  test("top level t-esc with undefined", () => {
+    const template = `<t t-esc="var"/>`;
+    expect(renderToString(template, { var: undefined })).toBe("");
+  });
+
   test("falsy values in text nodes", () => {
     const template = `
         <t t-esc="v1"/>:<t t-esc="v2"/>:<t t-esc="v3"/>:<t t-esc="v4"/>:<t t-esc="v5"/>`;

tests/compiler/t_out.test.ts

@@ -47,6 +47,21 @@ describe("t-out", () => {
     expect(renderToString(template, { var: new String("ok") })).toBe("<span>ok</span>");
   });
 
+  test("t-out with the 0 number", () => {
+    const template = `<t t-out="var"/>`;
+    expect(renderToString(template, { var: 0 })).toBe("0");
+  });
+
+  test("t-out with the 0 number, in a p", () => {
+    const template = `<p><t t-out="var"/></p>`;
+    expect(renderToString(template, { var: 0 })).toBe("<p>0</p>");
+  });
+
+  test("top level t-out with undefined", () => {
+    const template = `<t t-out="var"/>`;
+    expect(renderToString(template, { var: undefined })).toBe("");
+  });
+
   test("with an extended String class", () => {
     class LoveString extends String {
       valueOf(): string {

tests/compiler/t_set.test.ts

@@ -33,6 +33,22 @@ describe("t-set", () => {
     expect(renderToString(template, { value: "ok" })).toBe("<div>grimbergen</div>");
   });
 
+  test("t-set, multiple t-ifs, and a specific configuration", () => {
+    const template = `
+      <p>
+        <div>
+          <t t-if="flag" t-set="bouh" t-value="2"/>
+          <span>First div</span>
+        </div>
+        <div>
+          <t t-if="!flag">Second</t>
+        </div>
+      </p>`;
+    expect(renderToString(template)).toBe(
+      "<p><div><span>First div</span></div><div>Second</div></p>"
+    );
+  });
+
   test("set from body literal", () => {
     const template = `<t><t t-set="value">ok</t><t t-esc="value"/></t>`;
     expect(renderToString(template)).toBe("ok");

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

@@ -1308,6 +1308,18 @@ exports[`t-out in components can switch the contents of two t-out repeatedly 1`]
 }"
 `;
 
+exports[`t-out in components t-out and updating falsy values,  1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { safeOutput } = helpers;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return safeOutput(ctx['state'].a);
+  }
+}"
+`;
+
 exports[`t-out in components update properly on state changes 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

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

@@ -101,6 +101,72 @@ exports[`basics simple catchError 2`] = `
 }"
 `;
 
+exports[`can catch errors Errors have the right cause 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['state'].value);
+  }
+}"
+`;
+
+exports[`can catch errors Errors in owl lifecycle are wrapped in dev mode: async hook 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['state'].value);
+  }
+}"
+`;
+
+exports[`can catch errors Errors in owl lifecycle are wrapped out of dev mode: async hook 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['state'].value);
+  }
+}"
+`;
+
+exports[`can catch errors Errors in owl lifecycle are wrapped outside dev mode: sync hook 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['state'].value);
+  }
+}"
+`;
+
+exports[`can catch errors Thrown values that are not errors are wrapped in dev mode 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['state'].value);
+  }
+}"
+`;
+
+exports[`can catch errors Thrown values that are not errors are wrapped outside dev mode 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['state'].value);
+  }
+}"
+`;
+
 exports[`can catch errors an error in onWillDestroy 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
@@ -1296,3 +1362,16 @@ exports[`errors and promises errors in rerender 1`] = `
   }
 }"
 `;
+
+exports[`errors and promises wrapped errors in async code are correctly caught 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  let block1 = createBlock(\`<div>abc</div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    return block1();
+  }
+}"
+`;

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

@@ -43,7 +43,7 @@ exports[`list of components crash on duplicate key in dev mode 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
-  let { prepareList, withKey } = helpers;
+  let { prepareList, OwlError, withKey } = helpers;
   const comp1 = app.createComponent(\`Child\`, true, false, false, true);
   
   return function template(ctx, node, key = \\"\\") {
@@ -53,7 +53,7 @@ exports[`list of components crash on duplicate key in dev mode 1`] = `
     for (let i1 = 0; i1 < l_block1; i1++) {
       ctx[\`item\`] = v_block1[i1];
       const key1 = 'child';
-      if (keys1.has(key1)) { throw new Error(\`Got duplicate key in t-foreach: \${key1}\`)}
+      if (keys1.has(key1)) { throw new OwlError(\`Got duplicate key in t-foreach: \${key1}\`)}
       keys1.add(key1);
       const props1 = {};
       helpers.validateProps(\`Child\`, props1, ctx);

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

@@ -242,7 +242,7 @@ exports[`t-set t-set in t-if 1`] = `
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
   let { isBoundary, withDefault, setContextValue } = helpers;
   
-  let block1 = createBlock(\`<div><block-child-0/><block-child-0/><block-child-0/><p><block-text-0/></p></div>\`);
+  let block1 = createBlock(\`<div><p><block-text-0/></p></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
     ctx = Object.create(ctx);
@@ -307,7 +307,7 @@ exports[`t-set t-set outside modified in t-if 1`] = `
   let { text, createBlock, list, multi, html, toggler, comment } = bdom;
   let { isBoundary, withDefault, setContextValue } = helpers;
   
-  let block1 = createBlock(\`<div><block-child-0/><block-child-0/><block-child-0/><p><block-text-0/></p></div>\`);
+  let block1 = createBlock(\`<div><p><block-text-0/></p></div>\`);
   
   return function template(ctx, node, key = \\"\\") {
     ctx = Object.create(ctx);

tests/components/basics.test.ts

@@ -1084,4 +1084,25 @@ describe("t-out in components", () => {
     await nextTick();
     expect(fixture.innerHTML).toBe("<div>1</div><div>2</div>");
   });
+
+  test("t-out and updating falsy values, ", async () => {
+    class Test extends Component {
+      static template = xml`<t t-out="state.a"/>`;
+      state: any = useState({ a: 0 });
+    }
+
+    const comp = await mount(Test, fixture);
+    expect(fixture.innerHTML).toBe("0");
+    comp.state.a = undefined;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("");
+
+    comp.state.a = "hello";
+    await nextTick();
+    expect(fixture.innerHTML).toBe("hello");
+
+    comp.state.a = false;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("false");
+  });
 });

tests/components/error_handling.test.ts

@@ -19,6 +19,7 @@ import {
   snapshotEverything,
   useLogLifecycle,
 } from "../helpers";
+import { OwlError } from "../../src/runtime/error_handling";
 
 let fixture: HTMLElement;
 
@@ -159,16 +160,17 @@ describe("errors and promises", () => {
       static template = xml`<div><t t-esc="this.will.crash"/></div>`;
     }
 
-    let error: Error;
+    let error: OwlError;
     try {
       await mount(App, fixture);
     } catch (e) {
-      error = e as Error;
+      error = e as OwlError;
     }
     expect(error!).toBeDefined();
+    expect(error!.cause).toBeDefined();
     const regexp =
       /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
-    expect(error!.message).toMatch(regexp);
+    expect(error!.cause.message).toMatch(regexp);
     expect(mockConsoleError).toBeCalledTimes(0);
     expect(mockConsoleError).toBeCalledTimes(0);
   });
@@ -183,14 +185,15 @@ describe("errors and promises", () => {
       }
     }
 
-    let error: Error;
+    let error: OwlError;
     try {
       await mount(App, fixture);
     } catch (e) {
-      error = e as Error;
+      error = e as OwlError;
     }
     expect(error!).toBeDefined();
-    expect(error!.message).toBe("boom");
+    expect(error!.cause).toBeDefined();
+    expect(error!.cause.message).toBe("boom");
     expect(fixture.innerHTML).toBe("");
     expect(mockConsoleError).toBeCalledTimes(0);
     expect(mockConsoleWarn).toBeCalledTimes(1);
@@ -264,6 +267,30 @@ describe("errors and promises", () => {
     expect(error!.message).toBe("Tokenizer error: could not tokenize `{ 'invalid: 5 }`");
   });
 
+  test("wrapped errors in async code are correctly caught", async () => {
+    class Root extends Component {
+      static template = xml`<div>abc</div>`;
+      setup() {
+        onWillStart(async () => {
+          await Promise.resolve();
+          throw new Error("boom in onWillStart");
+        });
+      }
+    }
+
+    let error: any;
+    try {
+      await mount(Root, fixture, { test: true });
+    } catch (e) {
+      error = e;
+    }
+    expect(error!).toBeDefined();
+    expect(error!.message).toBe(
+      `The following error occurred in onWillStart: "boom in onWillStart"`
+    );
+    await new Promise((r) => setTimeout(r, 0)); // wait for the rejection event to bubble
+  });
+
   test("an error in willPatch call will reject the render promise", async () => {
     class Root extends Component {
       static template = xml`<div><t t-esc="val"/></div>`;
@@ -320,16 +347,17 @@ describe("errors and promises", () => {
       static components = { Child };
     }
 
-    let error: Error;
+    let error: OwlError;
     try {
       await mount(App, fixture);
     } catch (e) {
-      error = e as Error;
+      error = e as OwlError;
     }
     expect(error!).toBeDefined();
+    expect(error!.cause).toBeDefined();
     const regexp =
       /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
-    expect(error!.message).toMatch(regexp);
+    expect(error!.cause.message).toMatch(regexp);
     expect(mockConsoleError).toBeCalledTimes(0);
     expect(mockConsoleWarn).toBeCalledTimes(1);
   });
@@ -339,7 +367,7 @@ describe("errors and promises", () => {
       static template = xml`<div><t t-if="flag" t-esc="this.will.crash"/></div>`;
       flag = false;
       setup() {
-        onError((e) => (error = e));
+        onError(({ cause }) => (error = cause));
       }
     }
 
@@ -366,16 +394,17 @@ describe("errors and promises", () => {
       static components = { Child };
     }
 
-    let error: Error;
+    let error: OwlError;
     try {
       await mount(Parent, fixture);
     } catch (e) {
-      error = e as Error;
+      error = e as OwlError;
     }
     expect(error!).toBeDefined();
+    expect(error!.cause).toBeDefined();
     const regexp =
       /Cannot read properties of undefined \(reading 'y'\)|Cannot read property 'y' of undefined/g;
-    expect(error!.message).toMatch(regexp);
+    expect(error!.cause.message).toMatch(regexp);
     expect(mockConsoleError).toBeCalledTimes(0);
     expect(mockConsoleWarn).toBeCalledTimes(1);
   });
@@ -482,6 +511,146 @@ describe("can catch errors", () => {
     );
   });
 
+  test("Errors have the right cause", async () => {
+    const err = new Error("test error");
+    class Root extends Component {
+      static template = xml`<t t-esc="state.value"/>`;
+      state = useState({ value: 1 });
+
+      setup() {
+        onMounted(() => {
+          throw err;
+        });
+      }
+    }
+    let e: OwlError;
+    try {
+      await mount(Root, fixture, { test: true });
+    } catch (error) {
+      e = error as OwlError;
+    }
+    expect(e!.message).toBe(`The following error occurred in onMounted: "test error"`);
+    expect(e!.cause).toBe(err);
+  });
+
+  test("Errors in owl lifecycle are wrapped in dev mode: async hook", async () => {
+    const err = new Error("test error");
+    class Root extends Component {
+      static template = xml`<t t-esc="state.value"/>`;
+      state = useState({ value: 1 });
+
+      setup() {
+        onWillStart(async () => {
+          await nextMicroTick();
+          throw err;
+        });
+      }
+    }
+    let e: OwlError;
+    try {
+      await mount(Root, fixture, { test: true });
+    } catch (error) {
+      e = error as OwlError;
+    }
+    expect(e!.message).toBe(`The following error occurred in onWillStart: "test error"`);
+    expect(e!.cause).toBe(err);
+  });
+
+  test("Errors in owl lifecycle are wrapped outside dev mode: sync hook", async () => {
+    const err = new Error("test error");
+    class Root extends Component {
+      static template = xml`<t t-esc="state.value"/>`;
+      state = useState({ value: 1 });
+
+      setup() {
+        onMounted(() => {
+          throw err;
+        });
+      }
+    }
+    let e: OwlError;
+    try {
+      await mount(Root, fixture);
+    } catch (error) {
+      e = error as OwlError;
+    }
+    expect(e!.message).toBe(
+      `An error occured in the owl lifecycle (see this Error's "cause" property)`
+    );
+    expect(e!.cause).toBe(err);
+  });
+
+  test("Errors in owl lifecycle are wrapped out of dev mode: async hook", async () => {
+    const err = new Error("test error");
+    class Root extends Component {
+      static template = xml`<t t-esc="state.value"/>`;
+      state = useState({ value: 1 });
+
+      setup() {
+        onWillStart(async () => {
+          await nextMicroTick();
+          throw err;
+        });
+      }
+    }
+    let e: OwlError;
+    try {
+      await mount(Root, fixture);
+    } catch (error) {
+      e = error as OwlError;
+    }
+    expect(e!.message).toBe(
+      `An error occured in the owl lifecycle (see this Error's "cause" property)`
+    );
+    expect(e!.cause).toBe(err);
+  });
+
+  test("Thrown values that are not errors are wrapped in dev mode", async () => {
+    class Root extends Component {
+      static template = xml`<t t-esc="state.value"/>`;
+      state = useState({ value: 1 });
+
+      setup() {
+        onMounted(() => {
+          throw "This is not an error";
+        });
+      }
+    }
+    let e: OwlError;
+    try {
+      await mount(Root, fixture, { test: true });
+    } catch (error) {
+      e = error as OwlError;
+    }
+    expect(e!.message).toBe(
+      `Something that is not an Error was thrown in onMounted (see this Error's "cause" property)`
+    );
+    expect(e!.cause).toBe("This is not an error");
+  });
+
+  test("Thrown values that are not errors are wrapped outside dev mode", async () => {
+    class Root extends Component {
+      static template = xml`<t t-esc="state.value"/>`;
+      state = useState({ value: 1 });
+
+      setup() {
+        onMounted(() => {
+          throw "This is not an error";
+        });
+      }
+    }
+    let e: OwlError;
+    try {
+      await mount(Root, fixture);
+    } catch (error) {
+      e = error as OwlError;
+    }
+    expect(e!.message).toBe(
+      `An error occured in the owl lifecycle (see this Error's "cause" property)`
+    );
+    expect(e!.cause).toBe("This is not an error");
+  });
+
   test("can catch an error in the initial call of a component render function (parent mounted)", async () => {
     class ErrorComponent extends Component {
       static template = xml`<div>hey<t t-esc="state.this.will.crash"/></div>`;
@@ -1180,8 +1349,8 @@ describe("can catch errors", () => {
     class Catch extends Component {
       static template = xml`<t t-slot="default" />`;
       setup() {
-        onError((error) => {
-          this.props.onError(error);
+        onError(({ cause }) => {
+          this.props.onError(cause);
         });
       }
     }

tests/components/hooks.test.ts

@@ -653,7 +653,7 @@ describe("hooks", () => {
       try {
         await mount(MyComponent, fixture);
       } catch (e: any) {
-        expect(e.message).toBe("Intentional error");
+        expect(e.cause.message).toBe("Intentional error");
       }
       // no console.error because the error has been caught in this test
       expect(console.error).toHaveBeenCalledTimes(0);

tests/components/style_class.test.ts

@@ -1,3 +1,4 @@
+import { OwlError } from "../../src/runtime/error_handling";
 import { Component, mount, onMounted, useState, xml } from "../../src";
 import { makeTestFixture, nextTick, snapshotEverything } from "../helpers";
 
@@ -346,16 +347,17 @@ describe("style and class handling", () => {
       static template = xml`<Child class="'a'"/>`;
       static components = { Child };
     }
-    let error: Error;
+    let error: OwlError;
     try {
       await mount(ParentWidget, fixture);
     } catch (e) {
-      error = e as Error;
+      error = e as OwlError;
     }
     expect(error!).toBeDefined();
+    expect(error!.cause).toBeDefined();
     const regexp =
       /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
-    expect(error!.message).toMatch(regexp);
+    expect(error!.cause.message).toMatch(regexp);
     expect(fixture.innerHTML).toBe("");
     expect(mockConsoleWarn).toBeCalledTimes(1);
   });

tests/helpers.ts

@@ -19,6 +19,7 @@ import { helpers } from "../src/runtime/template_helpers";
 import { TemplateSet, globalTemplates } from "../src/runtime/template_set";
 import { BDom } from "../src/runtime/blockdom";
 import { compile } from "../src/compiler";
+import { OwlError } from "../src/runtime/error_handling";
 
 const mount = blockDom.mount;
 
@@ -221,7 +222,7 @@ export async function editInput(input: HTMLInputElement | HTMLTextAreaElement, v
 afterEach(() => {
   if (steps.length) {
     steps.splice(0);
-    throw new Error("Remaining steps! Should be checked by a .toBeLogged() assertion!");
+    throw new OwlError("Remaining steps! Should be checked by a .toBeLogged() assertion!");
   }
 });
 

tests/misc/portal.test.ts

@@ -1,3 +1,4 @@
+import { OwlError } from "../../src/runtime/error_handling";
 import {
   App,
   Component,
@@ -499,7 +500,7 @@ describe("Portal", () => {
         </div>`;
       state = { error: false };
       setup() {
-        onError((e) => (error = e));
+        onError(({ cause }) => (error = cause));
       }
     }
     addOutsideDiv(fixture);
@@ -958,14 +959,15 @@ describe("Portal: Props validation", () => {
           </t>
         </div>`;
     }
-    let error: Error;
+    let error: OwlError;
     try {
       await mount(Parent, fixture, { dev: true });
     } catch (e) {
-      error = e as Error;
+      error = e as OwlError;
     }
     expect(error!).toBeDefined();
-    expect(error!.message).toBe(`' ' is not a valid selector`);
+    expect(error!.cause).toBeDefined();
+    expect(error!.cause.message).toBe(`' ' is not a valid selector`);
   });
 
   test("target must be a valid selector 2", async () => {