Basic Vue.js support in MediaWiki

 Done

Vue.js is now shipped as part of MediaWiki core. JS code in skins and extensions can require( 'vue' ) from ResourceLoader just like any other module. Single-file components (.vue files) are supported via ResourceLoader. See here for guidelines about using Vue.js within MediaWiki.

Development of library of Codex components

In progress

Codex contains a library of components that is under active development. Components are built with Vue.js, and some components also have a CSS-only version that does not require JavaScript. Documentation for Codex can be found here.

• Some components are still being developed; developers may need to supplement Codex components with custom components suitable for their needs. Check out the list of components that we plan to add to Codex.
• This is an open-source project and contributions are welcome! Learn how to contribute a new or updated component.

To learn more about Codex, check out:

• Phabricator workboard (see the Design Systems Team workboard for sorted and prioritized tasks)
• Code (or GitHub mirror)
• Live demo site

Modern user interfaces for all users

In progress

Codex components are currently only available when modern JavaScript is available and once JavaScript has loaded, which would exclude users of older browsers. We would like to find a way to make user interfaces built with Codex work for these users as well.

• See timeline for current status

Design and define design tokens

 Done

Design tokens are the smallest pieces of our design system — specifically, they are named entities that store visual design attributes. We use them in place of hard-coded values (such as hex values for color or pixel values for spacing) in order to maintain a scalable and consistent visual system for UI development.

Design tokens are now available for use in MediaWiki.

Support for ES6 across MediaWiki

In progress

MediaWiki is using Vue 3, which dropped support for IE11. Features using Vue.js should ensure they are only delivered to modern browsers by setting "es6": true in their module definitions.

• Developers of skins and extensions are encouraged to start using ES6 features in their Vue.js code now; Wikimedia's eslint-config rules include a preset for vue3-es6 that will be useful here.
• This is in alignment with current guidelines about how to support legacy browsers like IE11 – in general new JS features should not target these browsers; if they must be supported, a server-rendered fallback should be defined.
• Support for ES6 in gadgets is currently limited due to lack of support in the JS syntax checker. See T75714 for more information.

Vue 2 to Vue 3 Migration

T289017

In progress

The provided copy of Vue has been upgraded to the Vue 3 Migration Build. By default, the library will still behave in alignment with the Vue 2 API, but users can opt-in to the Vue 3 behavior by setting appropriate compatibility flags in their code.

• Teams writing new Vue features should opt-in to Vue 3 behavior starting now.
• Teams maintaining existing features (written for Vue 2 originally) should start planning their migrations.
• Eventually the compatibility build will be removed (T289105), and all Vue code must be made Vue 3 compatible.

Get Vue.js from ResourceLoader

Developers should rely on the version of Vue that is already provided via ResourceLoader rather than bundling or vendoring their own copy of the library. Currently MW ships Vue 3 with the Compatibility Build included.

Developers of skins or extensions which list "vue" as a dependency in extension.json or skin.json can require the library as they would any other RL module.

const Vue = require( 'vue' );

Developers of gadgets, or of any feature where Vue is to be loaded conditionally, can load the Vue module on the client-side:

mw.loader.using( [ 'vue' ] ).then( function ( require ) {
    const Vue = require( 'vue' );
} );

Use Single-file components

MediaWiki supports Vue single-file components (aka .vue files) within any ResourceLoader module that is using the packageFiles feature. However, MediaWiki's support for single-file components is incomplete, and has the following limitations:

• <script setup=''> is not supported
• Advanced style features, such as <style scoped=''>, <style module=''>, and v-bind in styles are not supported
• Src Imports are not supported (but support for this feature could potentially be added, if developers find it useful)
• Pre-processors, such as <template lang="pug"> or <script lang='ts'> (TypeScript) are not supported. For styles, only <style lang='less'> is supported.
• LESS styles are processed using MediaWiki's LESS processor, which uses an old version of LESS. On the other hand, this means all the features supported in other LESS files in MediaWiki are supported here too.
• ES6 import and export are not supported. Instead of import, use require(); instead of export default { ... }; use module.exports = { ... };. Other ES6 syntax is supported.
• ES2016 and newer syntax is not supported. Notable examples of unsupported syntax include the spread operator in object literals ({ foo, ...bar }), async/await, and Object.values()/Object.entries().
• Self-closing tags for components (e.g. <my-component />) are not supported. Instead, you have to use open and close tags (e.g. <my-component></my-component>).
• Component tags using PascalCase (e.g. <MyComponent>) are not supported. Instead, you have to use kebab-case for component names (e.g. <my-component>).
• .vue files are only supported in package modules (modules that use packageFiles)

If you try to use an unsupported SFC feature, ResourceLoader will throw an error at runtime. Unsupported JS or template syntax results in a lint error, so make sure you set up linting for your code to catch these, as well as other pitfalls and style guideline violations.

Initialize with createMwApp()

To mount your component to the DOM, use Vue.createMwApp(). This function works the same as Vue.createApp(), but adds shared MediaWiki-specific plugins for internationalization and error logging. The code mounting your component should be in a simple init file that requires the top-level component (plus any stores and plugins) and mounts it to a placeholder div. Other logic and UI code should live in other files (for example, the top-level component) as much as possible. Conventionally, the top-level component file is called App.vue and the init file is called init.js, unless there are multiple entry points that each have their own top-level component.

A simple example of an init file would look like this:

var Vue = require( 'vue' ),
    App = require( './App.vue' );

// Assuming there's a <div id="my-component-placeholder"> on the page
Vue.createMwApp( App ).mount( '#my-component-placeholder' );

A more complex init file that uses a Vuex store and a custom plugin would look like this:

var Vue = require( 'vue' ),
    App = require( './App.vue' ),
    store = require( './store/index.js' ),
    fooPlugin = require( './plugins/foo.js' );

Vue.createMwApp( App )
    .use( store )
    .use( fooPlugin )
    // Assuming there's a <div id="my-component-placeholder"> on the page
    .mount( '#my-component-placeholder' );

Write Vue3-compatible code

MediaWiki uses the compatibility build of Vue 3. This means that Vue will try to provide compatibility with Vue 2 code by default, which breaks certain Vue 3 features (in particular v-model on components, and setting attributes to false). To avoid this breakage, all new code written for Vue 3 (and old code that has been fully migrated to Vue 3) must set compatConfig: { MODE: 3 } and compilerOptions: { whitespace: 'condense' } in the component definition of every component, like this:

// @vue/component
module.exports = exports = {
    // Enable Vue 3 mode with compatConfig and compilerOptions
    compatConfig: {
        MODE: 3
    },
    compilerOptions: {
        whitespace: 'condense'
    },
    // The rest of your component definition goes here:
    components: {
        // ...
    },
    data() {
        return {
            // ...
        };
    },
    methods: {
        // ...
    }
    // etc.
};

Once all old code written for Vue 2 has been migrated to Vue 3, MediaWiki will migrate to the non-compatibility build of Vue 3. Once that has happened, these compatConfig settings will no longer be necessary.

Don't rely on build tools or server-side rendering

In the wider Vue.js community, developers make frequent use of Node.js build tools like Vite, Rollup, Nuxt.js, etc. MediaWiki is a PHP application, and currently no Node.js service is available for use in production in WMF projects. For the time being, developers working with Vue in MediaWiki must limit themselves to client-side functionality only. The Design Systems Team is currently exploring ways to support a front-end build step or server-side component rendering, but this remains experimental.

Use Pinia for state management

Pinia is available in MediaWiki. Pinia is the new official state management library for use with Vue 3 and successor to Vuex 4. Pinia is recommended for new projects; for existing Vuex-based projects, MediaWiki also makes Vuex 4 available. See also the guide for Vuex to Pinia migrations.

The i18n plugin

The vue module comes with a small i18n plugin that wraps MediaWiki's i18n system (mw.message), so you can use MediaWiki i18n messages in your templates. This plugin creates an $i18n() function that you can use inside templates, which is an alias for mw.message(). For plain text messages (most cases), you can simply use:

<p>{{ $i18n( 'message-key' ) }}</p>

You can pass parameters either variadically, or as an array:

<p>{{ $i18n( 'message-key', param1, param2 ) }}</p>
<!-- or: -->
<p>{{ $i18n( 'message-key' ).params( [ param1, param2 ] ) }}</p>

The $i18n() function returns a Message object, so you can use it in all the same ways that you can use mw.message() in "normal" JS code. Remember that all message keys you use have to be added to the "messages" array in the ResourceLoader module definition.

<!-- Parsed message without parameters: -->
<p v-i18n-html:category-empty></p>

<!-- Parsed message with array of parameters: -->
<p v-i18n-html:namespace-protected="[ namespaceName ]"></p>

<!-- Parsed message with dynamic message name: -->
<p v-i18n-html="msgNameVariable"></p>

<template>
    <p v-i18n-html="fooOrBarMsg"></p>
</template>
<script>
module.exports = {
    computed: {
        fooOrBarMsg: function () {
            // Note that this returns a Message object, not a string
            return mw.message( this.foo ? 'foo-msg' : 'bar-msg' )
                .params( [ this.baz, this.quux ] );
        }
    }
};
</script>

Testing

You should write tests! The current recommendation is to use Jest.

See the Vue.js testing guide for more information about how to test Vue components in a MediaWiki environment.

Error reporting

Client side errors can be monitored in Logstash. Dedicated documentation forthcoming in T248884.

TypeScript

(coming soon)

IE 11

As MediaWiki is using Vue 3, any features built with it will not work with IE11. See Compatibility/IE11 for more information.

Most important

• Official guide
• Official API documentation
• Official style guide
• Official devtools browser extensions

Additional

• Mozilla Developer Network (MDN) Vue.js documentation

Training vendors

• Vue School
• Frontend Masters
• Vue Mastery (includes some free courses too)

From around MediaWiki

• Successful Technical RFC on evaluating front-end frameworks within the MediaWiki ecosystem
• 2020: The Year in Vue from the Wikimedia Tech Blog

External organizations choosing Vue