README

stencil-tailwind-plugin

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This package is used to integrate tailwindcss and StencilJS. This plugin for Stencil is specifically focused on the integration between tailwindcss v3.x and the Stencil build. While tailwindcss can be integrated into a Stencil build, this plugin aims to ease the integration, while providing an optimised inclusion of styles across the shadow DOM. For tailwind v2 support, please see the v0.6+ versions and branch.

This plugin also aims to allow users to make use of all the tailwindcss classes and postcss plugins like @apply. In such both styles of tailwindcss usage can be used in a single component. This plugin also aims to allow the use of object initialisers to conditionally set styles.

For an example of a basic Stencil integration, see the example.

Getting started

This guide assumes that a Stencil project has already been initialized and configured.

Installation

Install the necessary dependencies:

npm install -D stencil-tailwind-plugin tailwindcss

Configuration

In the Stencil configuration, consume the plugin:

// stencil.config.ts
import { Config } from '@stencil/core';
import tailwind from 'stencil-tailwind-plugin';

export const config: Config = {
  plugins: [
    tailwind()
  ],
  devServer: {
    reloadStrategy: 'pageReload'
  }
};

In some configurations, the reloadStrategy can be left as hmr but on occasions new styles are not applied as expected. For more on HMR, see below.

There are also a number of options that can be given to the plugin:

Property	Description	Default
`tailwindCssPath`	Path to a css file to read for tailwind css configuration. When not specified a default layers of @base, @utilities and @components are used.	`undefined`
`tailwindCssContents`	Instead of providing the file path, the plugin accepts string details. If both are supplied, the file contents will be taken as the source of truth ignoring this configuration	`@tailwind base;@tailwind utilities;@tailwind components;`
`tailwindConf`	Configuration object to be used for tailwind processing	The default set of tailwind options with `jit` enabled
`stripComments`	Indicate if the comment headers should be stripped as well	`false`
`minify`	Indicate if the css should be minified by using `cssnano`	`true`
`useAutoPrefixer`	Indicate if the auto-prefixer should be used used `autoprefixer`	`true`
`postcss`	Path to postcss configuration object or an object that contains the postcss configuration. If a `postcss` configuration is found in the default paths, it will be used.	`process.cwd()`

The default options can be referenced from the plugin as well:

// stencil.config.ts
import tailwind, { PluginOpts } from 'stencil-tailwind-plugin';

const opts = Object.assign({}, PluginOpts.DEFAULT, { debug: false, stripComments: true });

export const config: Config = {
  // ...
  plugins: [
    tailwind(opts)
  ],
  // ...
};

Postcss custom configuration

There are a number of postcss plugins that might be wanted when processing the tailwind output specifically. The nature of the stencil build makes it difficult to pass the custom css directly back into the css pipeline building. Hence, the postcss configuration can be completely overridden by specifying the postcss configuration path, or by creating a postcss configuration file.

The plugin uses the default postcss-load-config package. Hence, any the configuration options can be used as a file. If a postcss configuration file exists in the process.cwd(), then that postcss configuration will be used over the built-in postcss configuration.

The postcss config option can be used to specify the path. If the configuration file is not found in that path, the plugin will quietly fall over to use the built-in configuration. If there are modules not found, these will be reported to the user.

As an example of a postcss configuration that could be used:

// postcss.config.js
module.exports = {
  plugins: [
    require('postcss-import'),
    require('tailwindcss'),
    require('autoprefixer'),
    require('postcss-sort-media-queries'),
    require('postcss-combine-duplicated-selectors'),
    require('cssnano')
  ]
};

or as a Stencil configuration:

// stencil.config.ts
import tailwind from 'stencil-tailwind-plugin';

export const config: Config = {
  // ...
  plugins: [
    tailwind({
      postcss: {
        plugins: [
          require('postcss-import'),
          require('tailwindcss'),
          require('autoprefixer'),
        ]
      }
    })
  ],
  // ...
};

If the tailwindcss plugin is not specified, it is assumed that the plugins should be run before the default tailwind options. The tailwindcss plugin options will be overwritten by the tailwind configuration provided by the plugin, hence, the postcss tailwindcss is used as a marker for where tailwindcss should be used in the postcss chain of plugins.

Purge setup

Previously the plugin would enable purge options for web components. This introduced a number of behaviours that where difficult to resolve under situations. Hence the plugin no longer purges content. In large scale projects, the extra tailwind preflight settings can result in a bloated shadow DOM (for instance, targetting html and body in the shadow DOM doesn't do anything).

For purging of unused styles, the postcss plugin @fullhuman/postcss-purgecss can be used:

npm install -D @fullhuman/postcss-purgecss

The configuration of the purge plugin needs to be done with tailwind in mind. This regex may need to be tweaked for tailwind syntax moving forward:

// stencil.config.ts
import { Config } from '@stencil/core';
import tailwind from 'stencil-tailwind-plugin';
import tailwindcss from 'tailwindcss';
import { defaultExtractor } from 'tailwindcss/lib/lib/defaultExtractor';
import purgecss from '@fullhuman/postcss-purgecss';
import autoprefixer from 'autoprefixer';

export const config: Config = {
  outputTargets: [
    // ...
  ],
  plugins: [
    sass(),
    tailwind({
      tailwindConf,
      tailwindCssPath: './src/styles/tailwind.css',
      postcss: {
        plugins: [
          tailwindcss(),  // <-- used as a marker only, do not use for configuration, use tailwindConf
          autoprefixer(),
          purgecss({
            content: ['./**/*.tsx'],
            safelist: [
              ':root',
              ':host',
              ':shadow',
              '/deep/',
              '::part',
              '::theme'
            ],
            defaultExtractor
          }),
        ]
      }
    })
  ]
  // ...
};

This configuration uses the extractor from the tailwind library. Also, note, that the use of tailwindcss in the postcss as a marker.

Configuration with other plugins

It is important to note that when using sass files, that the sass Stencil plugin appears before the tailwind plugin. The sass plugin needs to process the sass files first before the raw css is pasted to the tailwind postcss processor. An example configuration could look like:

// stencil.config.ts
import { Config } from '@stencil/core';
import { sass } from '@stencil/sass';
import autoprefixer from 'autoprefixer';
import tailwind from 'stencil-tailwind-plugin';
import { inlineSvg } from 'stencil-inline-svg';
import tailwindConfig from './tailwind.config';

export const config: Config = {
  outputTargets: [ /* ... */],
  plugins: [
    inlineSvg(),
    sass({
      includePaths: [
        /* ... */
      ]
    }),
    tailwind({
      tailwindCssPath: './src/styles/tailwind.pcss',
      tailwindConf: tailwindConfig,
      postcss: {
        plugins: [
          autoprefixer()
        ]
      }
    }),
  ]

HMR considerations

Stencil's compiler does support HMR, however, for inline styles produced by tailwind, another plugin is required in order for the correct dependencies to be mapped to the file watcher. The HMR plugin can be included by:

// stencil.config.ts
import { Config } from '@stencil/core';
import tailwind, { tailwindHMR } from 'stencil-tailwind-plugin';

export const config: Config = {
  // ...
  plugins: [
    sass(),
    tailwind({
      tailwindConf,
      tailwindCssPath: './src/styles/tailwind.css'
    }),
    tailwindHMR()
  ]
};

The tailwindHMR plugin will register all the tsx files against the css files. This allows Stencil to watch for changes on those tsx files and update the css accordingly.

Unfortunately, as of v2.12.0 of the compiler, this cannot be done as a single plugin and two plugins are required.

Usage

This plugin hooks into the build process for Stencil. The tailwind JIT process run as a secondary build set and as such the css classes are applied after the component has been transpiled.

For an example of a basic Stencil integration, see the example.

Using @apply is `css`/`sass` files

The tailwind @apply directive can be used in any css/sass file as per tailwind spec:

.apply-styles {
  @apply text-red-100;
}

The @apply directive will be applied as expected:

.apply-styles {
  --tw-text-opacity: 1;
  color: rgba(254, 226, 226, var(--tw-text-opacity));
}

Using inline classes

Assuming a component declares a render function of:

render() {
  return (
    <div class="text-red-100">
      This is a test
    </div>
  );
}

Inline classes will be added to the component style definition.

Using conditional styles

Assuming a component declares a render function of:

render() {
  const styles = {
    'text-red-100': true,
    'text-red-200': this.someCondition
  };
  return (
    <div class={styles}>
      This is a test
    </div>
  );
}

In this case, both text-red-100 and text-red-200 styles will be added to the components style definition.

Using style urls

Assuming the component has declared:

@Component({
  tag: 'component',
  styleUrls: {
    md: 'component.md.scss',
    ios: 'component.ios.css',
  },
  shadow: true,
})

In this case, all tailwind styles will be added to both md and ios style definitions.

Caveat on Function Components

There are some issues around functional components when they are located in external files to a component. The plugin attempts to insert the Function Component styles into the host component and in so doing, the Stencil HMR does not detect the changes correctly and will require a rebuild when this happens.

As an example, given:

// component-A.tsx
import { FuncComp } from '../common/UtilsFunctionalComponents'

// rest of the normal component that uses <FuncComp />

And:

// component-B.tsx
import { FuncComp } from '../common/UtilsFunctionalComponents'

// rest of the normal component that uses <FuncComp />

And:

// common/UtilsFunctionalComponents.tsx
export const FuncComp: FunctionalComponent<FunctionalCompProps> = ({ name }) => (
  <h1 class="text-indigo-700">This is a functional one - Hello, {name}!</h1>
);

In this example, component-A and component-B will both contain the style definition for text-indigo-700 because they both import FuncComp.

If common/UtilsFunctionalComponents.tsx is updated, neither component-A.tsx or component-B.tsx will be build by Stencil's HMR, hence the style class change from FuncComp will not reflect.

Caveat on base reset styles

This plugin does not include base tailwind reset styles as this would bloat all the components with base styles. If based reset styles are required, the best is to place them in the :host selector. The plugin keeps the :host selector for being purged.

Peer Dependencies

This plugin requires the following peer dependencies:

tailwindcss
typescript

These are provided as peer dependencies so consumers can override the versions.

Development

Clone the repo and install the dependencies:

npm install

Run tests:

npm run tests

Honourable mentions

A lot of inspiration for this plugin was taken from the similarly named plugin, stencil-tailwind by Jack Rowlingson.

Inspiration also taken from proto-stencil-tailwind that moves stencil-tailwind forward by Richard Hess.

Special thanks to the above.

Usage no npm install needed!