Ember CLI Postcss
Installation
ember install ember-cli-postcss
Usage
The add-on can be used in two ways:
- on individual files, referred to as “compile”
- on all CSS files, referred to as “filter”
Note: it’s possible to use both compile and filter.
Additional Note: this app is compatible with Glimmer JS
Compile
This step will look for either app.css
or <project-name>.css
in your styles directory. Additional files to be processed can be defined in the output paths configuration object for your application:
const app = new EmberApp(defaults, {
outputPaths: {
app: {
html: 'index.html',
css: {
'app': '/assets/app.css',
'print': '/assets/print.css'
}
}
}
}
Filter
This step will run at the end of the build process on all CSS files, including the merged vendor.css
file and any CSS imported into the Broccoli tree by add-ons.
Files can be white-listed and/or black-listed by using the respective include and exclude options. Each accepts an array of file globs, which are then passed on to Broccoli Funnel. An example can be seen in the sample configuration below.
Configuring Plug-ins
There are two steps to setting up postcss with ember-cli-postcss
:
- install and require the node modules for any plug-ins
- provide the node module and plug-in options as a
postcssOptions
object inember-cli-build.js
The postcssOptions
object should have a “compile” and/or “filter” property, which will have the properties enabled
and plugins
, which is an array of objects that contain a module
property and an options
property:
Browser Targets
Some postcss plug-ins, like autoprefixer, allow you to configure which browsers to target for transpilation. When using Ember CLI >= 2.13.0, the browser targets configuration found in the file config/targets.js
will be added to each plug-in’s options (as options.browsers
). This browser list can be overwritten on a plug-in by plug-in basis. You can learn more about the targets feature on the Ember.js blog.
postcssOptions: {
compile: {
enabled: true, // defaults to true
browsers: ['last 3 versions'], // this will override config found in config/targets.js
plugins: [
{
module: <module>,
options: {
...
}
}
]
},
filter: {
enabled: true, // defaults to false
map: false, // defaults to inline, false in production
browsers: ['last 3 versions'], // this will override config found in config/targets.js
include: ['styles/*.css'],
exclude: ['vendor/bootstrap/**/*'],
processTrees: ['css'],
plugins: [
{
module: <module>,
options: {
...
}
}
]
}
}
Process Trees
When using the filter version of this add-on the default configuration is now to
only run on the css
tree. This will mean that the add-on is only run when CSS
files are changed. If you need the process to run on other trees or when other
files are changed, you should update the processTrees
option to include more
trees from the following list: [template, js, css, test, all,]
Example
Install the autoprefixer plug-in:
npm i --save-dev autoprefixer
Specify some plug-ins in your ember-cli-build.js
:
const EmberApp = require('ember-cli/lib/broccoli/ember-app');
const autoprefixer = require('autoprefixer');
module.exports = function (defaults) {
const app = new EmberApp(defaults, {
postcssOptions: {
compile: {
enabled: false,
},
filter: {
enabled: true,
plugins: [
{
module: autoprefixer,
options: {
browsers: ['last 2 versions'] // this will override the config, but just for this plugin
}
}
]
}
}
});
return app.toTree();
};
Compile Caching
When using the compile method, the default list of file extensions for caching is set to .css, .scss, .sass, .less
for faster incremental builds. If you are using a parser or filetype not in the list you will want to add the file extension as a regex to the cacheInclude
option.
If you are using something like Tailwind or a postcss plugin with a JS config file that you would like to trigger a rebuild, you will need to update the options to cache JS files: cacheInclude: [/.*\.(css|scss|sass|less|js)$/],
or more specifically cacheInclude: [/.*\.(css|scss)$/, /.tailwind\.js$/]
.
If you are using something like PurgeCSS and would like postcss to rebuild when tempalte files are updated, you will need to update the options to cache HBS files: cacheInclude: [/.*\.(css|scss|sass|less|hbs)$/],
. However, in most cases PurgeCSS should only be run for a production build and this shouldn't be necessary.
Example
postcssOptions: {
compile: {
enabled: true,
cacheExclude: [],
cacheInclude: [/.*\.(css|scss|sass|less)$/]
}
}
Developing Addons
If you are developing an addon and would like to use ember-cli-postcss
to process the CSS to automatically be included in the vendor.css
of Ember applications consuming the addon, there are 2 steps to follow.
- create your styles in
addon/styles/addon.css
(you can import other CSS files if a postcss import plugin is installed) - configure your addon’s options to process postcss:
// index.js
const CssImport = require('postcss-import')
const PresetEnv = require('postcss-preset-env');
const { join } = require('path');
const style_dir = join( __dirname, 'addon', 'styles');
module.exports = {
options: {
postcssOptions: {
compile: {
enabled: true,
includePaths: [style_dir],
plugins: [
{ module: CssImport },
{
module: PresetEnv,
options: { stage: 3 }
}
]
}
}
}
...
}
Migrating from other Processors
If you’d like to migrate a project from one of the other processors, such as Less, Sass, or Stylus, you can configure Postcss with an appropriate parser and set of plugins that provides an equivalent set of features.
This then allows you to use additional Postcss plugins at the end of the compilation to continue transforming your styles for more powerful control of authoring styles in your application. This also plays nicely with ember-component-css.
So far this migration process has been tested when switching from Sass.
Switching from Sass
One common use case is to transition from using Sass to Postcss or using them both together. As of ember-cli-postcss@3.7.0
this is possible with the right combination of options and plugins.
There are three key pieces of configuration:
- Set the parser to
postcss-scss
- Configure the extension to match your files (ie. 'scss')
- Use
@csstools/postcss-sass
as the first plugin
Your configuration options in ember-cli-build.js
would contain the following options for this addon:
postcssOptions: {
compile: {
extension: 'scss',
enabled: true,
parser: require('postcss-scss'),
plugins: [
{
module: require('@csstools/postcss-sass'),
options: {
includePaths: [
'node_modules/tachyons-sass',
],
},
},
...
],
},
...
}
This allows your to switch your CSS processing pipeline to use postcss without being hugely disruptive as you can keep the Sass features and .scss
or .sass
file extension. The importing feature of @csstools/postcss-sass
will also look for .css
files, so you can choose to gradually rename your files from Sass partials _<filename>.scss
to <filename>.css
without breaking anything.
If your goal is to completely move away from using Sass features you can remove the parser, remove the sass plugin, use an import plugin that fits your needs and ensure that your files have the .css
extension.
Experimental Features
Custom Properties Service
CSS variables are now supported by many major browsers. The values of these variables can be accessed, set, and removed using JavaScript. This addon now exports a service, which provides methods to work with CSS variables. Each method is a wrapper around the browser API, which includes a check for browser support before executing.
The service provides 3 methods:
getVal ({ element = docEl, variableName })
setVal ({ element = docEl, variableName, variableValue })
removeVal ({ element = docEl, variableName })
A Contrived Example:
import { inject } from '@ember/service'
export default <ember object>.extend({
customProperties: inject(),
...
nightMode() {
this.get('customProperties').setVal({variableName: '--background', variableValue: 'black'})
this.get('customProperties').setVal({variableName: '--text', variableValue: 'white'})
},
dayMode() {
this.get('customProperties').setVal({variableName: '--background', variableValue: 'white'})
this.get('customProperties').setVal({variableName: '--text', variableValue: 'black'})
},
})
Note: if you are using postcss-custom-properties, ensure you configure the option { preserve: true }