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https://github.com/dylanirlbeck/tailwind-ppx

A Reason/OCaml Pre-Processor eXtension (PPX) that validates your Tailwind classes at compile-time.
https://github.com/dylanirlbeck/tailwind-ppx

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

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README 

        
**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.**



---



# tailwind-ppx

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[![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors-)



A Reason/OCaml [Pre-Processor eXtension (PPX)](https://blog.hackages.io/reasonml-ppx-8ecd663d5640) that validates your Tailwind classes at compile-time. 






## Table of Contents



- [Features (Current and Upcoming)](#features)

- [Usage](#usage)

- [Configuration](#configuration)

- [Installation](#installation)

- [Frequently Asked Questions (FAQ)](#faq)

- [Developing](#developing)

- [Contributors](#contributors-)

- [Examples and Related Projects](#other)



## 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](#getting-ready-for-production) (with PurgeCSS and `tailwind-ppx`'s custom extractor function)

- [Ships with an integration script](#integration-script) that converts all your

  existing `className="..."` to `className=[%tw "..."]`



**Upcoming**



- [Better integration with PostCSS](https://github.com/dylanirlbeck/tailwind-ppx/issues/62)

- 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](https://github.com/dylanirlbeck/tailwind-ppx/issues)!



## 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:



```css

.flex {

  display: flex;

}



.flex-row {

  flex-direction: row;

}

```



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

examples:



```reason

// Example 1

 // This is ok!



// Example 2

 // ERROR: Class name not found: flex-ro. Did you mean flex-row?



// Example 3

 // 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](#-path) to your `tailwind.css` file (relative to your project root).



### Getting ready for production



As [outlined in the Tailwind docs](https://tailwindcss.com/docs/controlling-file-size/), 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](https://tailwindcss.com/docs/controlling-file-size/#setting-up-purgecss). 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`:



```javascript

// 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



```json

{

  "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:



```json

{

  "name": "gen-tailwind",

  "command": "tailwindcss build $in -o $out -c ../../tailwind.config.js"

}

```



You might have to [specify the path to `tailwind.css`](#-path).



### Autocompletion (Neovim only)



If you're a Neovim user, you can download the [`coc-tailwindcss`](https://github.com/iamcco/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`.



```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](https://github.com/dylanirlbeck/tailwind-ppx-demo).



### With `yarn` or `npm` on Bucklescript projects (recommended)



Install the PPX with `yarn` or `npm`



```bash

yarn add --dev @dylanirlbeck/tailwind-ppx

# Or

npm install --dev @dylanirlbeck/tailwind-ppx

```



And add the PPX in your `bsconfig.json` file:



```json

{

  "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`](https://github.com/MinimaHQ/re-classnames) in combination

  with `tailwind-ppx`. See the example below:



  ```reason

  module SomeComponent = {

    [@react.component]

    let make = (~someBool) => {

      let className =

        Cn.(

          [%tw "text-blue-500"]->on(someBool)

          + [%tw "text-gray-500"]->on(!someBool)

        );

      
;

    };

  };

  ```



- **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:



  ```reason

   // 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](https://semver.org/))

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](https://github.com/dylanirlbeck/tailwind-ppx/releases) 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](https://github.com/dylanirlbeck/tailwind-ppx/pull/116#issuecomment-657551562) 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](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!



## Other



### Examples



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



- [my-first-pr](https://github.com/dylanirlbeck/my-first-pr)



### Related Projects



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



- [ocaml-css-parser](https://github.com/astrada/ocaml-css-parser)

- [styled-ppx](https://github.com/davesnx/styled-ppx)

- [graphql-ppx](https://github.com/reasonml-community/graphql_ppx)