Neutrino Compile Loader Middleware

@neutrinojs/compile-loader is Neutrino middleware for compiling source code with Babel.

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Requirements

  • Node.js v6 LTS, v8, v9
  • Yarn v1.2.1+, or npm v5.4+
  • Neutrino v8

Installation

@neutrinojs/compile-loader can be installed via the Yarn or npm clients.

Yarn

❯ yarn add @neutrinojs/compile-loader

npm

npm install --save @neutrinojs/compile-loader

Usage

@neutrinojs/compile-loader can be consumed from the Neutrino API, middleware, or presets. Require this package and plug it into Neutrino:

// Using function middleware format

const compile = require('@neutrinojs/compile-loader');

neutrino.use(compile, {
  include: [],
  exclude: [],
  babel: {},
  ruleId: 'compile',
  useId: 'babel'
});
// Using object or array middleware format

module.exports = {
  use: [
    ['@neutrinojs/compile-loader', {
      include: [],
      exclude: [],
      babel: {},
      ruleId: 'compile',
      useId: 'babel'
    }]
  ]
};
  • include should be an array of paths to include in the compilation. Maps to webpack's Rule.include
  • exclude should be an array of paths to exclude from the compilation. Maps to webpack's Rule.exclude
  • babel is a Babel configuration object, consumed by babel-loader. Use this to set properties such as presets, plugins, and env.
  • ruleId is the identifier to the compiler loader rule. Override this to add an additional compile-loader instance
  • useId is the identifier for the babel loader. Override this to change the identifier.

Merging Babel Configuration

This package also exposes a function for merging Babel configurations. This comes from the babel-merge package.

const { merge } = require('@neutrinojs/compile-loader');

const together = merge(
  {
    presets: [
      ['babel-preset-env', {
        targets: {
          browsers: ['latest 1 Chrome']
        }
      }]
    ]
  },
  {
    presets: [
      ['babel-preset-env', {
        targets: {
          browsers: ['latest 1 Firefox']
        }
      }]
    ]
  }
);

console.log(together);

// Logs:
{
  presets: [
    ['babel-preset-env', {
      targets: {
        browsers: [
          'latest 1 Chrome',
          'latest 1 Firefox'
        ]
      }
    }]
  ]
}

Advanced merging

Should you need to do merging of Babel configuration that is more advanced than this, such as re-ordering the options, you will need to tap into the existing Babel options to do so. This still involves using the compile-loader's merge function.

Example: enable current decorator syntax in the compile loader:

const { merge } = require('@neutrinojs/compile-loader');

// Decorators generally need to be enabled *before* other
// syntax which exists in both normal plugins, and
// development environment plugins.
// Tap into the existing Babel options and merge our
// decorator options *before* the rest of the existing
// Babel options
config.module
  .rule('compile')
    .use('babel')
      .tap(options => merge({
        plugins: [
          require.resolve('babel-plugin-transform-decorators-legacy'),
          require.resolve('babel-plugin-transform-class-properties')
        ]
      }, options));

Customization

@neutrinojs/compile-loader creates some conventions to make overriding the configuration easier once you are ready to make changes.

Rules

The following is a list of rules and their identifiers which can be overridden:

Name Description Environments and Commands
compile Compiles JS and JSX files from the src directory using Babel. Contains a single loader named babel. all

Contributing

This middleware is part of the neutrino-dev repository, a monorepo containing all resources for developing Neutrino and its core presets and middleware. Follow the contributing guide for details.

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