Migrating to Aurelia 2
Aurelia 2 is a complete rewrite of Aurelia that shares many of the same loved and familiar features of Aurelia 1. Understandably, in the spirit of progress, not everything is the same. In this section, we are going to guide you through what has changed and how you can migrate over your Aurelia 1 applications to Aurelia 2.
MIGRATION WORKFLOW
Option 1: Quick Start with Compat Package (Recommended for Initial Migration)
The fastest way to get your AU1 application running in AU2 is to use the compatibility package. This approach lets you get a working AU2 application first, then gradually migrate features.
Step 1: Create a new AU2 project
npx makes aurelia new-project
cd new-project
npm install @aurelia/compat-v1
Step 2: Copy your AU1 source files
Copy your
src/
directory from your AU1 projectCopy any custom configuration files (excluding
aurelia_project/
)
Step 3: Update your main.ts
import { Aurelia } from 'aurelia';
import { compatRegistration } from '@aurelia/compat-v1';
import { MyApp } from './my-app';
Aurelia
.register(compatRegistration)
.app(MyApp)
.start();
Step 4: Update package.json dependencies Remove AU1 dependencies and ensure you have the AU2 equivalents:
Remove:
aurelia-framework
,aurelia-bootstrapper
, etc.Add:
aurelia
,@aurelia/compat-v1
Option 2: Manual Migration (For New AU2 Features)
If you want to fully embrace AU2 features from the start:
Step 1: Project Structure
src/
main.ts # Entry point (same location as AU1)
my-app.ts # Root component (skeleton default)
my-app.html # Root template (skeleton default)
components/ # Your components
resources/ # Custom elements, attributes, etc.
Step 2: Bootstrapping Migration
AU1 main.ts:
import { Aurelia } from 'aurelia-framework';
import { PLATFORM } from 'aurelia-pal';
export function configure(aurelia: Aurelia): void {
aurelia.use
.standardConfiguration()
.feature(PLATFORM.moduleName('resources/index'));
aurelia.start().then(() => aurelia.setRoot(PLATFORM.moduleName('app')));
}
AU2 main.ts:
import { Aurelia } from 'aurelia';
import { MyApp } from './my-app';
Aurelia
.app(MyApp)
.start();
Step 3: Router Migration
AU1 router config:
import { Router, RouterConfiguration } from 'aurelia-router';
export class App {
router: Router;
configureRouter(config: RouterConfiguration, router: Router): void {
config.title = 'My App';
config.map([
{ route: ['', 'home'], name: 'home', moduleId: PLATFORM.moduleName('./home') }
]);
this.router = router;
}
}
AU2 router config:
import { IRoute } from '@aurelia/router';
export class App {
static routes: IRoute[] = [
{ path: ['', 'home'], component: () => import('./home') }
];
}
Navigation in AU2:
import { IRouter, resolve } from 'aurelia';
export class MyComponent {
private readonly router = resolve(IRouter);
async navigateToHome() {
await this.router.load('home');
}
}
Critical Breaking Changes That Require Code Changes
1. Compose Element - MAJOR BREAKING CHANGE
AU1 compose:
<!-- AU1 - used module paths -->
<compose view-model.bind="'./components/user-card'" model.bind="user"></compose>
<compose view.bind="'./templates/user-template.html'" view-model.bind="user"></compose>
AU2 au-compose - DOES NOT WORK WITH MODULE PATHS:
<!-- AU2 - requires imported components or template strings -->
<au-compose component.bind="UserCard" model.bind="user"></au-compose>
<au-compose template.bind="userTemplate" model.bind="user"></au-compose>
Migration Required:
// AU1 - Dynamic module loading with strings
export class MyComponent {
componentPath = './components/user-card';
}
// AU2 - Must import components or use template strings
import { UserCard } from './components/user-card';
export class MyComponent {
userCard = UserCard; // Component class
// OR
userTemplate = '<div>${name}</div>'; // Template string
}
If you need dynamic component loading in AU2, you must create a module loader:
// Custom loader for dynamic components
const componentMap = new Map([
['user-card', () => import('./components/user-card')],
['admin-panel', () => import('./components/admin-panel')]
]);
async loadComponent(name: string) {
const loader = componentMap.get(name);
if (loader) {
const module = await loader();
return module.default || module[Object.keys(module)[0]];
}
return null;
}
2. Module Loading - No More PLATFORM.moduleName
AU1:
config.map([
{ route: 'users', moduleId: PLATFORM.moduleName('./pages/users') }
]);
AU2:
static routes: IRoute[] = [
{ path: 'users', component: () => import('./pages/users') }
];
AU1 feature loading:
aurelia.use.feature(PLATFORM.moduleName('resources/index'));
AU2 - Create a resources array to register globally:
// resources/index.ts - AU2 pattern
import { MyCustomElement } from './my-custom-element';
import { MyValueConverter } from './my-value-converter';
import { MyBindingBehavior } from './my-binding-behavior';
export const GlobalResources = [
MyCustomElement,
MyValueConverter,
MyBindingBehavior,
];
// main.ts
import { GlobalResources } from './resources/index';
import { MyApp } from './my-app';
Aurelia
.register(...GlobalResources)
.app(MyApp)
.start();
3. Other Critical Changes
Binding commands: Replace
.delegate
with.trigger
Replaceable parts: Replace with
<au-slot>
elementsView decorators: Replace
@noView
/@inlineView
withtemplate
propertyEvent preventDefault: No longer automatic - use
.trigger:prevent
when needed
COMPAT PACKAGE
An quickest way to get an application in v1 up an running in v2 is to include the compat package. It can be done via 2 steps:
installing the compat package via
npm install @aurelia/compat-v1
include the compat package into your app:
import { compatRegistration } from '@aurelia/compat-v1';
...
Aurelia
.register(compatRegistration, ...)
.app(...)
.start()
BREAKING CHANGES
Event
In v2, preventDefault
is no longer called by default. This breaking change could show up in unexpected places:
click events: in v1, clicking on a button inside a form will not submit the form, while it will in v2, as the click event default behavior is no longer prevented {% hint style="info" %} Even though clicking default behavior is not prevented, form submission without an action will not reload the page as this default behavior is still prevented in v2, so you don't need to add
:prevent
to every buttonclick
, or formsubmit
listener. {% endhint %}- drag events: in v1, implementing drag/drop will havepreventDefault
called automatically, but in v2, they will need to be explicitly called by the application
Sometimes, if it's desirable to call preventDefault
in an event binding, use prevent
modifier, like the following example:
<button click.trigger:prevent="doWork()">Submit manually</button>
<div dragstart.trigger="prepareDragdrop()" drop.trigger:prevent="onDrop()">
Read more about modifiers in event modifier doc here
Scope selection
In v2, when trying to bind with a non-existent property, the closest boundary scope (scope of the owning custom element) will be selected, instead of the immediate scope of the binding (v1 behavior).
Internal binding property observeProperty
has been renamed to observe
observeProperty
has been renamed to observe
In v1, if you happen to use .observeProperty
method from bindings in your application/library, then change it to observe
instead. The parameters of the signature remain the same.
Internal binding property sourceExpression
has been renamed to ast
sourceExpression
has been renamed to ast
In v1, if you happen to use .sourceExpression
property from bindings in your application/library, then change it to ast
instead. The type of the property remains the same.
Enhance API changes:
In v1, enhance
method on an Aurelia
instance has the signature:
class Aurelia {
...
enhance(elementOrConfig: Element | IEnhancementConfig): View;
}
In v2, enhance
method on an Aurelia
instance has the signature:
interface IAurelia {
...
enhance(enhancementConfig: IEnhancementConfig): IEnhancedView;
}
Parent container and resources can be specified through this config.
View model ref binding (view-model.ref="...")
In v2, in order to get a reference to the underlying component view model, use component.ref
instead of view-model.ref This is to make terminologies consistent as we are moving towards component oriented terms.
If attribute (if.bind="...")
The primary property of
If
has been renamed fromcondition
tovalue
. If you are usingif.bind
, you are not affected. If you are using the multi prop binding syntax, the template looks like this:
<div if="condition.bind: yes">
Change it to:
<div if="value.bind: yes">
Binding Engine
BindingEngine
has been removed in v2, but can still be imported from@aurelia/compat-v1
package for ease of migration. ThecollectionObserver
method on the compat package ofBindingEngine
is not the same with v1, per the follow comparison: v2collectionObserver(collection): { subscribe: (callback: (collection, indexMap)) => { dispose(): void } }
v1
collectionObserver(collection): { subscribe: (callback: (collection, splices)) => { dispose(): void } }
Binding commands
.delegate
command has been removed, use.trigger
instead. With shadow DOM, even though.delegate
works, it doesn't feel as natural as.trigger
, and the performance benefits.delegate
command used to give when browsers were slow adding many event listeners is no longer as big..call
command has been removed, use lambda functions instead to create function that preserves thethis
context. Refer to lambda expression
Compose
<compose>
has been renamed to<au-compose>
. The bindable properties of this component have also been changed:viewModel -> component
view -> template
model remains the same
Examples migration fix:
v1: <compose view.bind="..."> <compose view-model.bind="..."> v2: <au-compose template.bind="..."> <au-compose component.bind="...">
In Aurelia 2, all bindings are passed through to the underlying custom element composition, so
component.ref
(view-model.ref
in v1) no longer means getting a reference to the composer, but the composed view model instead.
Read more about dynamic composition in v2 in this dynamic composition doc and dynamic ui composition doc.
Replaceable & replaceable part
If you are using replaceable
/part
/repaceable-part
combo in your v1 applications, you'll need to replace them with <au-slot>
elements and au-slot
attributes. Refer to the au slot doc for more information.
View decorators
When migrating from v1, it is possible to encounter the @noView
and @inlineView
decorators. These decorators are no longer available from the core packages in v2. Instead, use the template
property of the custom element decorator.
For the ease of migration, the @noView
and @inlineView
decorators are made available from the @aurelia/compat-v1
package. FOllowing are some example usages.
Use the
@inlineView
decorator to define the template of a custom element.import { customElement } from 'aurelia'; import { inlineView } from '@aurelia/compat-v1'; @inlineView('foo-bar') @customElement('app-loader') export class AppLoader { //... }
Use the
@noView
decorator to define a custom element without a view.import { customElement } from 'aurelia'; import { noView } from '@aurelia/compat-v1'; @noView @customElement('loading-indicator') export class LoadingIndicator { // ... }
General changes
Custom attributes are no longer considered to have a binding to the primary bindable when their template usage is with an empty string, like the following examples:
<div my-attr> <div my-attr="">
Both of the above usages will be considered as "plain" usage, to avoid overriding the defaul value in the custom attribute component instance.
Templates no longer need to have
<template>
tags as the start and ending tags. Templates can be pure HTML with enhanced Aurelia markup but<template>
doesn't need to be explicitly defined.PLATFORM.moduleName
is gone. This was to address a limitation in Aurelia 1. Aurelia 2 now works well with all bundlers and does not require the addition of this code to use code splitting or tell the bundler where template code is.Better intellisense support for TypeScript applications. Using the new injection interfaces, you can now inject strongly typed Aurelia packages such as Fetch Client, Router or Internationalization. These packages are prefixed with an "I" such as
IHttpClient
,IRouter
and so on.empty binding expressions are automatically inferred based on the target of the binding, like the following example:
<input value.bind> <input value.bind="">
means:
<input value.bind="value">
This is automatically applied to
.bind
/.one-time
/.to-view
/.from-view
/.two-way
/.attr
binding commands.
Plugins:
Web-Components plugin
Remove automatic
au-
prefixRemove auto-conversion of Aurelia element -> WC element. Applications need to explicitly define this. This should make mix-matching & controlling things easier.
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