Babel preset for Griffel

A Babel preset that performs build time transforms for @griffel/react.

- Install
- Usage
- Importing Griffel from custom packages
- Configuring Babel settings
- Configuring module evaluation
- Transforms
- Example
- Access CSS output from code
- Troubleshooting
- Module evaluation

> [!CAUTION]
> We don't recommend to use this preset directly, it's intended to be used by other tools like webpack loader or Vite plugin.

Install

``bash
yarn add --dev @griffel/babel-preset


or


npm install --save-dev @griffel/babel-preset
`

Usage

.babelrc

`json
{
"presets": ["@griffel"]
}
`

$3

`js
import { makeStyles } from 'custom-package';
// 👇 custom import names are also supported
import { createStyles } from 'custom-package';
`

By default, preset handles imports from @griffel/react & @fluentui/react-components, to handle imports from custom packages settings should be tweaked:

`json
{
"presets": [
[
"@griffel",
{
"modules": [{ "moduleSource": "custom-package", "importName": "makeStyles" }]
}
]
]
}
`

> Note: "custom-package" should re-export __styles function from @griffel/react

$3

If you need to specify custom Babel configuration, you can pass them to babelOptions. These options will be used by the preset when parsing and evaluating modules.

`json
{
"presets": [
[
"@griffel",
{
"babelOptions": {
"plugins": ["@babel/plugin-proposal-class-static-block"],
"presets": ["@babel/preset-typescript"]
}
}
]
]
}
`

$3

`json
{
"presets": [
[
"@griffel",
{
"evaluationRules": []
}
]
]
}
`

The set of rules that defines how the matched files will be transformed during the evaluation. EvalRule is an object with two fields:

- test is a regular expression or a function (path: string) => boolean
- action is an Evaluator function, "ignore" or a name of the module that exports Evaluator function as a default export

_If test is omitted, the rule is applicable for all the files._

The last matched rule is used for transformation. If the last matched action for a file is "ignore" the file will be evaluated as is, so that file must not contain any js code that cannot be executed in nodejs environment (it's usually true for any lib in node_modules).

If you need to compile certain modules under /node_modules/ (which can be the case in monorepo projects), it's recommended to do it on a module by module basis for faster transforms, e.g. ignore: /node_modules\/\\/.

The default setup is:

`js
module.exports = {
presets: [
[
'@griffel',
{
evaluationRules: [
{
action: require('@griffel/babel-preset').shakerEvaluator,
},
{
test: /[/\\]node_modules[/\\]/,
action: 'ignore',
},
],
},
],
],
};
`

Transforms

This preset is designed to perform build time transforms for @griffel/react, it supports both ES modules and CommonJS, thus can be used in post-processing after TypeScript, for example.

Transforms applied by this preset allow stripping runtime part of makeStyles() and improve performance.

Example

Transforms

`js
import { makeStyles } from '@griffel/react';

const useStyles = makeStyles({
root: { color: 'red' },
});
`

roughly to

`js
import { __styles } from '@griffel/react';

const useStyles = __styles(/ resolved styles /);
`

Access CSS output from code

It's possible to configure the preset to return all the evaluated styles of a file. This
metadata looks something like below:

`ts
const output = {
// makeStyles
cssEntries: {
// by each hook
useStyles1: {
// by each slot
root: [".fxxxxx { color: 'red' }"],
},
useStyles2: {
root: [".fxxxxx { color: 'red' }"],
},
},
// makeResetStyles
cssResetEntries: {
// by each hook
useResetStyles1: [".fxxxxx { color: 'red' }"],
useResetStyles2: [".fxxxxx { color: 'red' }"],
},
};
`

This is intended for programmatic transforms in code so that they can be reused by other tooling without extra steps to determine
the output styles

`ts
import { griffelPreset, BabelPluginMetadata } from '@griffel/babel-preset';

const babelFileResult = Babel.transformFromAstSync(babelAST, sourceCode, {
babelrc: false,
configFile: false,
presets: [[griffelPreset, { generateMetadata: true }]],

filename: options.filename,

sourceMaps: options.enableSourceMaps,
sourceFileName: options.filename,
inputSourceMap: options.inputSourceMap,
});

// metadata
console.log(babelFileResult.metadata as unknown as BabelPluginMetadata);
`

Troubleshooting

This section focuses mainly on troubleshooting this babel preset in the microsoft/fluentui repo.
However, the concepts are not coupled to the repo setup.

$3

The preset uses tools from linaria to evaluate runtime calls of makeStyles.
Linaria's debugging documentation can help here.

Debugging output can be activated with following environment variables:

`sh
$ DEBUG=linaria\* LINARIA_LOG=debug yarn build
`

On Windows it's required to set environment variables via set or you can use cross-env, for example:

`sh
$ cross-env DEBUG=linaria\* LINARIA_LOG=debug yarn build
`

The debug output will include:

- Prepared code
- Evaluated code
- AST that indicates what code has been shaken with @linaria/shaker`