Coming from the Vue ecosystem, where vue cli makes it a breeze to get up and running, it was a bit of a struggle coming to Sapper/Svelte and trying to put all the pieces together.

Goal

A Sapper project with Postcss, Tailwind and the ability to import css files from node_modules packages and a single npm run dev to get going.

Many thanks to this article: A simpler way to add TailwindCSS to your Svelte project for an up to date way to add tailwind to a svelte project.

Step 1: Clone the starter template

npx degit "sveltejs/sapper-template#rollup" my-app
cd my-app
npm i

Step 2: Install requirements

npm i --D svelte-preprocess rollup-plugin-svelte postcss-load-config postcss-import postcss-nested postcss-cli tailwindcss npm-run-all

Step 3: Configure tailwind

npx tailwind init

Edit the resulting tailwind.config.js and add the required rules to the purgecss block to ensure svelte's styles are not removed:

module.exports = {
  purge: ["./src/**/*.svelte"],
  theme: {
    extend: {},
  },
  variants: {},
  plugins: [],
};

Edit /static/global.css with the following:

@tailwind base;
@tailwind components;
@tailwind utilities;

Step 4: Configure PostCSS and svelte-preprocess

In the root of your project, create and edit postcss.config.js as follows (this will be used by the postcss-cli to compile the above global.css to index.css):

module.exports = {
  plugins: [
    require("postcss-import"),
    require("postcss-nested"),
    require("tailwindcss")
  ],
}

Edit rollup.config.js by adding import sveltePreprocess from 'svelte-preprocess'; at the top of the file and instantiate like so:

const preprocess = sveltePreprocess({
  postcss: {
    plugins: [
      require('postcss-import')(),
      require('postcss-nested')()
    ]
  }
});

// Add the above

export default { ...

Add preprocess to the svelte object in both the client and server:

client: {
  ...
  plugins: [
    ...
    svelte({
      preprocess,
      dev,
      ...
},
server: {
  ...
  plugins: [
    ...
    svelte({
      preprocess,
      generate: 'ssr',
      ...
}

Step 5: Adjust run scripts

In /my-app/package.json, adjust the scripts block as follows:

"scripts": {
  "dev": "run-p start:dev watch:css",
  "build": "npm run build:css && sapper build --legacy",
  "watch:css": "postcss static/global.css -o static/index.css -w",
  "build:css": "NODE_ENV=production postcss static/global.css -o static/index.css",
  "export": "sapper export --legacy",
  "start": "node __sapper__/build",
  "start:dev": "sapper dev",
  "cy:run": "cypress run",
  "cy:open": "cypress open",
  "test": "run-p --race dev cy:run"
}

Basically, the adjusted dev script uses npm-run-all to run the tasks to compile tailwind and run sapper from the new start:dev script. If you need to run sapper on another port, you can adjust it so: "start:dev": "sapper dev --port 8080".

Step 6: Adjust the css import in the template

Edit /src/template.html ahd replace <link rel='stylesheet' href='global.css'> with <link rel='stylesheet' href='index.css'>

Step 7: Import css in svelte

So this is where things get a bit complicated.

Let's take Tippy.js as an example.

npm i -D tippy.js

You can add a tooltip to the default index.svelte like so:

<h1 data-tippy-content="Hello World">Great success!</h1>
...

To instantiate tippy, you have to do so inside an onMount to prevent a document is not defined error caused on the server-side:

<script>
  import { onMount } from "svelte";
  onMount(async () => {
    const { default: tippy } = await import("tippy.js");
    tippy('[data-tippy-content]');
  });
</script>

Now, to import the relevant css, you would think to simply add @import 'tippy.js/dist/tippy.css'; to the top of your style block.

However, this will result in endless Unused CSS selector errors. The way around this is to set the style block to global like so:

<style global>
  @import 'tippy.js/dist/tippy.css';
  ...
</style>

Of course, this now has the caveat that all styles within the block are now global, and you can have only one style block per component.

Seeing as this css needs to be applied globally to avoid the compiler errors and being stripped, I think it makes the most sense to simply place the import in global.css and allow the external postcss-cli to take care of things:

/* /static/global.css */
@import 'tippy.js/dist/tippy.css';
@tailwind base;
@tailwind components;
@tailwind utilities;

This way, the svelte compiler doesn't need to worry about these css imports on each save, and from our setup, we have the functionality of postcss within our components (though we lose the hot reload functionality).

Step 8: Run & build

A simple npm run dev and you are ready to work. To build for production, npm run build.

I'm completely new to svelte, so can't help but feel like this is being hacky – if anyone knows of a better way to handle things, please let me know.

Versions used in this writeup:

"postcss-cli": "^7.1.1",
"postcss-import": "^12.0.1",
"postcss-load-config": "^2.1.0",
"rollup-plugin-svelte": "^5.2.2",
"sapper": "^0.27.0",
"svelte": "^3.0.0",
"svelte-preprocess": "^3.9.7",
"tailwindcss": "^1.4.6",

Going Further

I'd recommend Snowpack with Svelte, Typescript and Tailwind CSS is a very pleasant surprise and actually many other articles on Ilia Mikhailov's blog where he's been writing about svelte a fair bit lately.