141 lines
6.6 KiB
Markdown
141 lines
6.6 KiB
Markdown
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# Resolve URL Loader
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[](https://www.npmjs.com/package/resolve-url-loader)
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This **webpack loader** allows you to have a distributed set SCSS files and assets co-located with those SCSS files.
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## Do you organise your SCSS and assets by feature?
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Where are your assets?
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* ✅ I want my assets all over the place, next to my SCSS files.
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* ❌ My assets are in a single directory.
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How complicated is your SASS?
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* ✅ I have a deep SASS composition with partials importing other partials.
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* ✅ My asset paths are constructed by functions or `@mixin`s.
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* ❌ I have a single SCSS file. The asset paths are just explicit in that.
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What asset paths are you using?
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* ✅ Fully relative `url(./foo.png)` or `url(foo.png)`
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* ❌ Root relative `url(/foo.png)`
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* ❌ Relative to some package or webpack root `url(~stuff/foo.png`)
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* ❌ Relative to some variable which is your single asset directory `url($variable/foo.png)`
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What webpack errors are you getting?
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* ✅ Webpack can't find the relative asset `foo.png` 😞
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* ❌ Webpack says it doesn't have a loader for `fully/resolved/path/foo.png` 😕
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If you can tick at least 1 item in **all of these questions** then use this loader. It will allow webpack to find assets with **fully relative paths**.
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If for any question you can't tick _any_ items then webpack should be able to already find your assets. You don't need this loader. 🤷
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Once webpack resolves your assets (even if it complains about loading them) then this loading is working correctly. 👍
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## What's the problem with SASS?
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When you use **fully relative paths** in `url()` statements then Webpack expects to find those assets next to the root SCSS file, regardless of where you specify the `url()`.
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To illustrate here are 3 simple examples of SASS and Webpack _without_ `resolve-url-loader`.
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[](docs/basic-problem.svg)
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The first 2 cases are trivial and work fine. The asset is specified in the root SCSS file and Webpack finds it.
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But any practical SASS composition will have nested SCSS files, as in the 3rd case. Here Webpack cannot find the asset.
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```
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Module not found: Can't resolve './cool.png' in '/absolute/path/.../my-project/src/styles.scss'
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```
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The path we present to Webpack really needs to be `./subdir/cool.png` but we don't want to write that in our SCSS. 😒
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Luckily we can use `resolve-url-loader` to do the **url re-writing** and make it work. 😊🎉
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With functions and mixins and multiple nesting it gets more complicated. Read more detail in [how the loader works](docs/how-it-works.md). 🤓
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## Getting started
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> **Upgrading?** the [changelog](CHANGELOG.md) shows how to migrate your webpack config.
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### Install
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via npm
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```bash
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npm install resolve-url-loader --save-dev
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```
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via yarn
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```bash
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yarn add resolve-url-loader --dev
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```
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### Configure Webpack
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The typical use case is `resolve-url-loader` between `sass-loader` and `css-loader`.
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**⚠️ IMPORTANT**
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* **source-maps required** for loaders preceding `resolve-url-loader` (regardless of `devtool`).
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* Always use **full loader package name** (don't omit `-loader`) otherwise you can get errors that are hard to debug.
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``` javascript
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rules: [
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{
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test: /\.scss$/,
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use: [
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...
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{
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loader: 'css-loader',
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options: {...}
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}, {
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loader: 'resolve-url-loader',
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options: {...}
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}, {
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loader: 'sass-loader',
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options: {
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sourceMap: true,
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sourceMapContents: false
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}
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}
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]
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},
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...
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]
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```
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## Options
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The loader should work without options but use these as required.
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| option | type | default | | description |
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|-------------|----------------------------|-----------------------------------------|------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| `sourceMap` | boolean | `false` | | Generate an outgoing source-map. |
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| `removeCR` | boolean | `true` Windows OS<br/>`false` otherwise | | Convert orphan CR to whitespace.<br/>See known issues below. |
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| `debug` | boolean | `false` | | Display debug information. |
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| `silent` | boolean | `false` | | Do **not** display warnings or deprecation messages. |
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| `root` | string | _unset_ | | Similar to the (now defunct) option in `css-loader`.<br/>This string, possibly empty, is prepended to absolute URIs.<br/>Absolute URIs are only processed if this option is set. |
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| `join` | function | _inbuilt_ | advanced | Custom join function.<br/>Use custom javascript to fix asset paths on a per-case basis.<br/>Refer to the [advanced features](docs/advanced-features.md) docs. |
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| `engine` | `'rework'`<br/>`'postcss'` | `'postcss'` | deprecated | The css parser engine.<br/>Using this option produces a deprecation warning. |
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## Limitations
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### Compatiblity
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Tested `macOS` and `Windows`.
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All `webpack2`-`webpack4` with contemporaneous loaders/plugins using `node 8.9`. And `webpack5` with latest loaders/plugins using `node 10.0`.
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Refer to `test` directory for full webpack configurations as used in automated tests.
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Some edge cases with `libsass` on `Windows` (see [troubleshooting](docs/troubleshooting.md) docs).
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### Known issues
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Read the [troubleshooting](docs/troubleshooting.md) docs before raising an issue.
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