postcss-import

What is postcss-import?

The postcss-import npm package is a plugin for PostCSS that allows you to import local files, node modules, or web_modules into your CSS files. It can be used to modularize your CSS and help manage large stylesheets by splitting them into smaller, more maintainable pieces.

What are postcss-import's main functionalities?

Importing local files

Allows you to import a local CSS file into another CSS file. This is useful for splitting your CSS into smaller, more manageable files.

@import 'local-file.css';

Importing node modules

Enables you to import CSS from a node module installed in your project's node_modules directory. This is useful for including third-party stylesheets in your project.

@import 'npm-module-name';

Importing from web_modules

Allows you to import CSS from web_modules, which can be useful if you are using a package manager that supports this feature, like Snowpack.

@import 'web-module-name';

Customizing import paths

Lets you customize the paths where postcss-import looks for CSS files to import. This is helpful when you have a specific directory structure and want to keep your imports clean and relative to those paths.

postcss([ require('postcss-import')({ path: ['src/css', 'src/styles'] }) ]);

Other packages similar to postcss-import

postcss-easy-import

A wrapper around postcss-import that adds glob pattern importing and other features. It is similar to postcss-import but with additional options for ease of use.

postcss-partial-import

Another PostCSS plugin that allows you to import partials. It is similar to postcss-import but with a focus on partials and includes features like prefixing and extension omission.

postcss-advanced-variables

While not solely focused on importing, this plugin extends CSS with variables, conditionals, and iterators that can be imported from other files. It offers a different set of features compared to postcss-import, which is focused on importing CSS files.

README

postcss-import

PostCSS plugin to transform @import rules by inlining content.

This plugin can consume local files, node modules or web_modules. To resolve path of an @import rule, it can look into root directory (by default process.cwd()), web_modules, node_modules or local modules. When importing a module, it will look for index.css or file referenced in package.json in the style or main fields. You can also provide manually multiples paths where to look at.

Notes:

• This plugin should probably be used as the first plugin of your list. This way, other plugins will work on the AST as if there were only a single file to process, and will probably work as you can expect.
• This plugin works great with postcss-url plugin, which will allow you to adjust assets url() (or even inline them) after inlining imported files.
• In order to optimize output, this plugin will only import a file once on a given scope (root, media query...). Tests are made from the path & the content of imported files (using a hash table). If this behavior is not what you want, look at skipDuplicates option
• If you are looking for glob, or sass like imports (prefixed partials), please look at postcss-easy-import (which use this plugin under the hood).
• This plugin attempts to follow the CSS @import spec; @import statements must precede all other statements (besides @charset).

Installation

$ npm install postcss-import

Usage

If your stylesheets are not in the same place where you run postcss (process.cwd()), you will need to use from option to make relative imports work from input dirname.

// dependencies
var fs = require("fs")
var postcss = require("postcss")
var atImport = require("postcss-import")

// css to be processed
var css = fs.readFileSync("css/input.css", "utf8")

// process css
postcss()
  .use(atImport())
  .process(css, {
    // `from` option is required so relative import can work from input dirname
    from: "css/input.css"
  })
  .then(function (result) {
    var output = result.css

    console.log(output)
  })

Using this input.css:

/* can consume `node_modules`, `web_modules` or local modules */
@import "cssrecipes-defaults"; /* == @import "./node_modules/cssrecipes-defaults/index.css"; */
@import "normalize.css"; /* == @import "./node_modules/normalize.css/normalize.css"; */

@import "css/foo.css"; /* relative to stylesheets/ according to `from` option above */

@import "css/bar.css" (min-width: 25em);

body {
  background: black;
}

will give you:

/* ... content of ./node_modules/cssrecipes-defaults/index.css */
/* ... content of ./node_modules/normalize.css/normalize.css */

/* ... content of foo.css */

@media (min-width: 25em) {
/* ... content of bar.css */
}

body {
  background: black;
}

Checkout tests for more examples.

Options

root

Type: String
Default: process.cwd() or dirname of the postcss from

Define the root where to resolve path (eg: place where node_modules are). Should not be used that much.
Note: nested @import will additionally benefit of the relative dirname of imported files.

path

Type: String|Array
Default: []

A string or an array of paths in where to look for files.

transform

Type: Function
Default: null

A function to transform the content of imported files. Take one argument (file content) and should return the modified content or a resolved promise with it. undefined result will be skipped.

transform: function(css) {
  return postcss([somePlugin]).process(css).then(function(result) {
    return result.css;
  });
}

plugins

Type: Array
Default: undefined

An array of plugins to be applied on each imported files.

onImport

Type: Function
Default: null

Function called after the import process. Take one argument (array of imported files).

resolve

Type: Function
Default: null

You can overwrite the default path resolving way by setting this option. This function gets (id, basedir, importOptions) arguments and returns full path, array of paths or promise resolving paths. You can use resolve for that.

load

Type: Function
Default: null

You can overwrite the default loading way by setting this option. This function gets (filename, importOptions) arguments and returns content or promised content.

skipDuplicates

Type: Boolean
Default: true

By default, similar files (based on the same content) are being skipped. It's to optimize output and skip similar files like normalize.css for example. If this behavior is not what you want, just set this option to false to disable it.

addDependencyTo

Type: Object
Default: null

An object with addDependency() method, taking file path as an argument. Called whenever a file is imported. You can use it for hot-reloading in webpack postcss-loader like this:

postcss: function(webpack) {
  return [
    require('postcss-import')({
      addDependencyTo: webpack
      /* Is equivalent to
      onImport: function (files) {
        files.forEach(this.addDependency)
      }.bind(webpack)
      */
    })
  ]
}

Example with some options

var postcss = require("postcss")
var atImport = require("postcss-import")

postcss()
  .use(atImport({
    path: ["src/css"],
    transform: require("css-whitespace")
  }))
  .process(cssString)
  .then(function (result) {
    var css = result.css
  })

---

CONTRIBUTING

• ⇄ Pull requests and ★ Stars are always welcome.
• For bugs and feature requests, please create an issue.
• Pull requests must be accompanied by passing automated tests ($ npm test).

Changelog

License