@griffel/babel-preset v1.5.8

Babel preset for Griffel

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

• Install
• When to use it?
• Usage
  • Importing Griffel from custom packages
  • Configuring Babel settings
  • Configuring module evaluation
• Transforms
• Example
• Access CSS output from code
• Troubleshooting
  • Module evaluation

Install

yarn add --dev @griffel/babel-preset
# or
npm install --save-dev @griffel/babel-preset

When to use it?

• For library developers, please use the Babel preset (this package)
• For application developers, please use @griffel/webpack-loader

Usage

.babelrc

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

Importing Griffel from custom packages

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:

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

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

Configuring Babel settings

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.

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

Configuring module evaluation

{
  "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[\/\\](?!some-module|other-module)/.

The default setup is:

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

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

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

roughly to

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:

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

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.

Module evaluation

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:

$ 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:

$ 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