Repository files navigation

webpack loader for Vue Single-File Components

• Documentation

• experimentalInlineMatchResource: boolean: enableInline matchResource for rule matching for vue-loader.

• reactivityTransform: boolean: enableVue Reactivity Transform (SFCs only).

• refSugar: boolean:removed. usereactivityTransform instead.

• customElement: boolean | RegExp: enable custom elements mode. An SFC loaded in custom elements mode inlines its<style> tags as strings under the component'sstyles option. When used withdefineCustomElement from Vue core, the styles will be injected into the custom element's shadow root.

  • Default is/\.ce\.vue$/
  • Setting totrue will process all.vue files in custom element mode.

• enableTsInTemplate: boolean (16.8+): allow TS expressions in templates when<script> haslang="ts". Defaults totrue.

  • When used withts-loader, due tots-loader's cache invalidation behavior, it sometimes prevents the template from being hot-reloaded in isolation, causing the component to reload despite only the template being edited. If this is annoying, you can set this option tofalse (and avoid using TS expressions in templates).

  • Alternatively, leave this option on (by default) and useesbuild-loader to transpile TS instead, which doesn't suffer from this problem (it's also a lot faster). However, do note you will need to rely on TS type checking from other sources (e.g. IDE orvue-tsc).

vue-loader is a loader forwebpack that allows you to author Vue components in a format calledSingle-File Components (SFCs):

<template>  <divclass="example">{{ msg }}</div></template><script>exportdefault {data() {return {      msg:'Hello world!',    }  },}</script><style>.example {color:red;}</style>

There are many cool features provided byvue-loader:

• Allows using other webpack loaders for each part of a Vue component, for example Sass for<style> and Pug for<template>;
• Allows custom blocks in a.vue file that can have custom loader chains applied to them;
• Treat static assets referenced in<style> and<template> as module dependencies and handle them with webpack loaders;
• Simulate scoped CSS for each component;
• State-preserving hot-reloading during development.

In a nutshell, the combination of webpack andvue-loader gives you a modern, flexible and extremely powerful front-end workflow for authoring Vue.js applications.

The following section is for maintainers and contributors who are interested in the internal implementation details ofvue-loader, and isnot required knowledge for end users.

vue-loader is not a simple source transform loader. It handles each language blocks inside an SFC with its own dedicated loader chain (you can think of each block as a "virtual module"), and finally assembles the blocks together into the final module. Here's a brief overview of how the whole thing works:

1. vue-loader parses the SFC source code into anSFC Descriptor using@vue/compiler-sfc. It then generates an import for each language block so the actual returned module code looks like this:

   // code returned from the main loader for 'source.vue'// import the <template> blockimportrenderfrom'source.vue?vue&type=template'// import the <script> blockimportscriptfrom'source.vue?vue&type=script'export*from'source.vue?vue&type=script'// import <style> blocksimport'source.vue?vue&type=style&index=1'script.render=renderexportdefaultscript

   Notice how the code is importingsource.vue itself, but with different request queries for each block.

2. We want the content inscript block to be treated like.js files (and if it's<script lang="ts">, we want to to be treated like.ts files). Same for other language blocks. So we want webpack to apply any configured module rules that matches.js also to requests that look likesource.vue?vue&type=script. This is whatVueLoaderPlugin (src/plugins.ts) does: for each module rule in the webpack config, it creates a modified clone that targets corresponding Vue language block requests.

   Suppose we have configuredbabel-loader for all*.js files. That rule will be cloned and applied to Vue SFC<script> blocks as well. Internally to webpack, a request like

   importscriptfrom'source.vue?vue&type=script'

   Will expand to:

   importscriptfrom'babel-loader!vue-loader!source.vue?vue&type=script'

   Notice thevue-loader is also matched becausevue-loader are applied to.vue files.

   Similarly, if you have configuredstyle-loader +css-loader +sass-loader for*.scss files:

   <stylescopedlang="scss">

   Will be returned byvue-loader as:

   import'source.vue?vue&type=style&index=1&scoped&lang=scss'

   And webpack will expand it to:

   import'style-loader!css-loader!sass-loader!vue-loader!source.vue?vue&type=style&index=1&scoped&lang=scss'

3. When processing the expanded requests, the mainvue-loader will get invoked again. This time though, the loader notices that the request has queries and is targeting a specific block only. So it selects (src/select.ts) the inner content of the target block and passes it on to the loaders matched after it.

4. For the<script> block, this is pretty much it. For<template> and<style> blocks though, a few extra tasks need to be performed:

   • We need to compile the template using the Vue template compiler;
   • We need to post-process the CSS in<style scoped> blocks,aftercss-loader butbeforestyle-loader.

   Technically, these are additional loaders (src/templateLoader.ts andsrc/stylePostLoader.ts) that need to be injected into the expanded loader chain. It would be very complicated if the end users have to configure this themselves, soVueLoaderPlugin also injects a globalPitching Loader (src/pitcher.ts) that intercepts Vue<template> and<style> requests and injects the necessary loaders. The final requests look like the following:

   // <template lang="pug">import'vue-loader/template-loader!pug-loader!source.vue?vue&type=template'// <style scoped lang="scss">import'style-loader!vue-loader/style-post-loader!css-loader!sass-loader!vue-loader!source.vue?vue&type=style&index=1&scoped&lang=scss'