Note: As of 08/16/2021, tailwind-ppx is now in archive-mode. I have been out of the Reason/ReScript community for some time now, but if anyone wants to take over as owner please let me know. Thank you to all involved for making this project successful.

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tailwind-ppx

A Reason/OCaml Pre-Processor eXtension (PPX) that validates your Tailwind classes at compile-time.

Table of Contents

• Features (Current and Upcoming)
• Usage
• Configuration
• Installation
• Frequently Asked Questions (FAQ)
• Developing
• Contributors
• Examples and Related Projects

Features

Current

• Checks for invalid class names (and suggestions for valid ones!)
• Checks for duplicate class names
• Always in-sync with your tailwind.css file (just make sure to re-build!)
• Automatic purging of unused class names (with PurgeCSS and tailwind-ppx's custom extractor function)
• Ships with an integration script that converts all your existing className="..." to className=[%tw "..."]

Upcoming

• Better integration with PostCSS
• Checks for redundant class names (like having both flex-row and flex-col)
• Checks for class name dependencies (like having flex-row without flex)

If you have ideas for new features, please open an issue!

Usage

tailwind_ppx implements a ppx (%tw) that validates your Tailwind CSS classes at compile time.

For example, for the following (condensed) tailwind.css file:

.flex {
  display: flex;
}

.flex-row {
  flex-direction: row;
}

tailwind-ppx will provide validation for your desired class names. See these examples:

// Example 1
<Component className=[%tw "flex flex-row"] /> // This is ok!

// Example 2
<Component className=[%tw "flex flex-ro"] /> // ERROR: Class name not found: flex-ro. Did you mean flex-row?

// Example 3
<Component className=[%tw "flex flex-row flex"] /> // ERROR: Duplicate class name: flex

Finally, tailwind-ppx requires your generated tailwind.css file to exist somewhere in the project hierarchy. Though not required, it's recommended that you configure the path to your tailwind.css file (relative to your project root).

Getting ready for production

As outlined in the Tailwind docs, when preparing for production you'll want to make sure that the only CSS from Tailwind that ends up in your bundle is CSS that you actually use in your code.

First, take a second to read the section on setting up Purgecss from the Tailwind docs. In order to help with the process outlined in the docs, this package ships with a default extractor function that'll take care of ensuring that any CSS from Tailwind that you aren't using with this PPX can be purged from your production CSS bundle. You enable it by slightly modifying the official example of how to set up your postcss.config.js:

// postcss.config.js
const purgecss = require("@fullhuman/postcss-purgecss")({
  // Specify the paths to all ReasonML code where you're using this PPX.
  content: ["./src/**/*.re"],

  // Include the extractor from this package
  defaultExtractor: require("@dylanirlbeck/tailwind-ppx").extractor
});

module.exports = {
  plugins: [
    require("tailwindcss"),
    require("autoprefixer"),
    ...(process.env.NODE_ENV === "production" ? [purgecss] : [])
  ]
};

Doing this will ensure that you only ship CSS from Tailwind to production that you're actually using with this PPX.

Moving or changing your tailwind.css file

If your tailwind.css file changes (or you move it) you'll need to rebuild your project - for example, bsb -clean-world and bsb -make-world if in BuckleScript. At this time, tailwind-ppx does not automatically watch for changes, though this is on the roadmap.

Alternatively, you can add the following rules to you bsconfig.json to re-trigger builds

{
  "sources": [
    {
      "dir": "src",
      "subdirs": true,
      "generators": [
        {
          "name": "gen-tailwind",
          "edge": ["tailwind.css", ":", "styles.css"]
        }
      ]
    }
  ],
  "generators": [
    {
      "name": "gen-tailwind",
      "command": "tailwindcss build $in -o $out"
    }
  ]
}

If you have a custom tailwind config file, you'll need to pass it to the tailwindcss command:

{
  "name": "gen-tailwind",
  "command": "tailwindcss build $in -o $out -c ../../tailwind.config.js"
}

You might have to specify the path to tailwind.css.

Autocompletion (Neovim only)

If you're a Neovim user, you can download the coc-tailwindcss extension to get class name autocompletion while using tailwind-ppx - just make sure to define a tailwind.config.js file. See the example below!

Ignore .tailwind_ppx_cache in your version control

tailwind-ppx will generate a .tailwind_ppx_cache folder in your project root to optimize the validation performance. If you're using a version control system, you don't need to check it in.

Configuration

-path

By default, tailwind-ppx looks for your tailwind.css file in the root directory. If tailwind.css lives elsewhere (or the name of your generated CSS file is different), you'll need to specify the file path in your bsconfig.json.

"ppx-flags": [
  ["tailwind-ppx", "-path ../path/to/tailwind.css",]
],

Installation

The most likely use case for tailwind-ppx is inside ReasonReact projects (using BuckleScript). To get started, we recommend cloning our demo project.

With yarn or npm on Bucklescript projects (recommended)

Install the PPX with yarn or npm

yarn add --dev @dylanirlbeck/tailwind-ppx
# Or
npm install --dev @dylanirlbeck/tailwind-ppx

And add the PPX in your bsconfig.json file:

{
  "ppx-flags": ["tailwind-ppx"]
}

Integration script

The @dylanirlbeck/tailwind-ppx NPM package ships with an executable that, when run in a BuckleScript project, turns all instances of className="..." into className=[%tw "..."]. The script is designed to make it easy to immediately introduce tailwind-ppx into an existing codebase.

You can use this script by running the following command from the root of your project (just make sure you've installed the NPM package).

yarn use-tailwind-ppx
# Or
npx use-tailwind-ppx

Note that you'll need both a bsconfig.json to exist in the project hierarchy and compiled project with bsb -make-world (so the lib/ directory exists in the project root) for the script to work properly.

FAQ

• How can I conditionally add classes?

  This feature is out of scope for tailwind-ppx; instead, we recommend you use re-classnames in combination with tailwind-ppx. See the example below:

  module SomeComponent = {
    [@react.component]
    let make = (~someBool) => {
      let className =
        Cn.(
          [%tw "text-blue-500"]->on(someBool)
          + [%tw "text-gray-500"]->on(!someBool)
        );
      <div className />;
    };
  };

• How can I use custom CSS classes?

  tailwind-ppx directly parses your generated tailwind.css file, which means that all CSS classes will be validated by the PPX, including custom class names defined in your base index.css/styles.css file. In short, if the class is in your tailwind.css file, it will be validated correctly by the ppx.

  Example:

  <Component className=[%tw "flex flex-row customLayou"] /> // ERROR: Class name not found: customLayou. Did you mean customLayout?

Developing

After cloning the repository, you should run esy to install the project dependencies. After that, you should be good to start developing!

Relevant commands

• esy build -> Builds the project
• esy format -> Formats the entire project with ocamlformat and refmt
• esy watch -> Watches for changes to Reason/OCaml files in the entire project, including in the /test directory
• esy test_native -> Runs the native tests (in test/native)
• cd test/bucklescript && yarn test -> Runs the BuckleScript tests (in test/bucklescript)

Note that if you pull requests are not formatted properly, or the esy.lock is out-of-date, GitHub actions will automatically format your code by pushing up a new commit.

Releasing (for maintainers)

1. Bump the version of the ppx in esy.json on master (we use semantic versioning)
2. Create and push a new tag

$ git checkout master
$ git tag vx.y.z
$ git push origin vx.y.z

3. Create detailed release notes for the new version, following the Added/Changed/Fixed/Removed format. Note that the new version of the PPX will automatically be pushed to NPM and a release will be created on GitHub.
4. Make sure that for any merged pull requests/closed issues were noticed by the all-contributors bot -- see this PR for an example of adding a new contributor who's PR was merged.

Contributors ✨

Thanks goes to these wonderful people:

Dylan Irlbeck 💻 📖	Corentin Leruth 💻 🤔 🚧	Gabriel Nordeborn 💻 🤔	Brad Dunn 💻 🐛	Thomas Coopman 🐛 📖	Manas 📖	Peter Piekarczyk 🤔
Patrick Kilgore 📖	ahzm 💻 📖 🤔	Joseph Price 💻	Vladimir Danchenkov 📖	Jonas Zeitler 💻	Pete Shaw 💻

This project follows the all-contributors specification. Contributions of any kind welcome!

Other

Examples

These projects are using tailwind-ppx throughout the code base:

• my-first-pr

Related Projects

The following amazing projects provided a lot of inspiration; I recommend you check them out!

• ocaml-css-parser
• styled-ppx
• graphql-ppx