TaskCluster Neutrino Node.js Preset

neutrino-preset-taskcluster is a Neutrino preset that supports building TaskCluster Node.js applications.

Features

Extends from neutrino-preset-node:

• Zero upfront configuration necessary to start developing and building a Node.js project
• Modern Babel compilation supporting ES modules, Node.js 6.9+, async functions, and dynamic imports
• Supports automatically-wired sourcemaps
• Tree-shaking to create smaller bundles
• Hot Module Replacement with source-watching during development
• Chunking of external dependencies apart from application code
• TaskCluster's ESLint rules baked in
• Easily extensible to customize your project as needed

Requirements

• Node.js v6.9+
• Yarn or npm client
• Neutrino v5

Installation

neutrino-preset-taskcluster can be installed via the Yarn or npm clients. Inside your project, make sure neutrino and neutrino-preset-taskcluster are development dependencies.

Yarn

❯ yarn add --dev neutrino neutrino-preset-taskcluster

npm

❯ npm install --save-dev neutrino neutrino-preset-taskcluster

If you want to have automatically wired sourcemaps added to your project, add source-map-support:

Yarn

❯ yarn add source-map-support

npm

❯ npm install --save source-map-support

Project Layout

neutrino-preset-taskcluster follows the standard project layout specified by Neutrino. This means that by default all project source code should live in a directory named src in the root of the project. This includes JavaScript files that would be available to your compiled project.

Quickstart

After installing Neutrino and the TaskCluster preset, add a new directory named src in the root of the project, with a single JS file named index.js in it.

❯ mkdir src && touch src/index.js

Edit your src/index.js file with the following:

import { createServer } from 'http';

const delay = ms => new Promise(resolve => setTimeout(resolve, ms));
const port = process.env.PORT || 3000;

createServer(async (req, res) => {
  await delay(500);
  console.log('Request!');
  res.end('hi!');
})
.listen(port, () => console.log(`Server running on port ${port}`));

Now edit your project's package.json to add commands for starting and building the application.

{
  "scripts": {
    "start": "neutrino start --use neutrino-preset-taskcluster",
    "build": "neutrino build --use neutrino-preset-taskcluster"
  }
}

Start the app, then either open a browser to http://localhost:3000 or use curl from another terminal window:

Yarn

❯ yarn start
Server running on port 3000

❯ curl http://localhost:3000
hi!

npm

❯ npm start
Server running on port 3000

❯ curl http://localhost:3000
hi!

Building

neutrino-preset-taskcluster builds assets to the build directory by default when running neutrino build. Using the quick start example above as a reference:

❯ yarn build
clean-webpack-plugin: /taskcluster/build has been removed.
Build completed in 0.419s

Hash: 89e4fb250fc535920ba4
Version: webpack 2.5.1
Time: 424ms
       Asset     Size  Chunks             Chunk Names
    index.js  4.29 kB       0  [emitted]  index
index.js.map  3.73 kB       0  [emitted]  index
✨  Done in 1.51s.

You can either serve or deploy the contents of this build directory as a Node.js module, server, or tool. For Node.js this usually means adding a main property to package.json pointing to the built entry point. Also when publishing your project to npm, consider excluding your src directory by using the files property to whitelist build, or via .npmignore to blacklist src.

{
  "main": "build/index.js",
  "files": [
    "build"
  ]
}

Note: While this preset works well for many types of Node.js applications, it's important to make the distinction between applications and libraries. This preset will not work optimally out of the box for creating distributable libraries, and will take a little extra customization to make them suitable for that purpose.

Hot Module Replacement

While neutrino-preset-taskcluster supports Hot Module Replacement for your app, it does require some application-specific changes in order to operate. Your application should define split points for which to accept modules to reload using module.hot:

For example:

import { createServer } from 'http';
import app from './app';

if (module.hot) {
  module.hot.accept('./app');
}

createServer((req, res) => {
  res.end(app('example'));  
}).listen(/* */);

Or for all paths:

import { createServer } from 'http';
import app from './app';

if (module.hot) {
  module.hot.accept();
}

createServer((req, res) => {
  res.end(app('example'));  
}).listen(/* */);

Using dynamic imports with import() will automatically create split points and hot replace those modules upon modification during development. Using the import() pseudo-function also enables importing modules conditionally and on demand.

Customizing

To override the build configuration, start with the documentation on customization. neutrino-preset-node, which this preset extends, creates some conventions to make overriding the configuration easier once you are ready to make changes.

By default the Node.js preset creates a single main index entry point to your application, and this maps to the index.js file in the src directory. This means that the Node.js preset is optimized toward a main entry to your app. Code not imported in the hierarchy of the index entry will not be output to the bundle. To overcome this you must either define more entry points, or import the code path somewhere along the index hierarchy.

Vendoring

This preset automatically vendors all external dependencies into a separate chunk based on their inclusion in your package.json. No extra work is required to make this work.

Rules

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

• compile: Compiles JS files from the src directory using Babel. Contains a single loader named babel.
• lint: Lints JS files from the src directory using ESLint. Contains a single loader named eslint.

Plugins

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

• banner: Injects source-map-support into the entry point of your application if detected in dependencies or devDependencies of your package.json.
• copy: Copies non-JS files from src to build when using neutrino build.
• clean: Clears the contents of build prior to creating a production bundle.

Simple customization

By following the customization guide and knowing the rule, loader, and plugin IDs above, you can override and augment the build directly from package.json.

Compile targets

This preset uses babel-preset-env to compile code targeting Node.js v6.9+. To change the Node.js target from package.json, specify an object at neutrino.options.compile.targets which contains a babel-preset-env-compatible Node.js target.

Example: Replace the preset Node.js target with support for Node.js 4.2:

{
  "neutrino": {
    "options": {
      "compile": {
        "targets": {
          "node": 4.2
        }
      }
    }
  }
}

Example: Change support to current Node.js version:

{
  "neutrino": {
    "options": {
      "compile": {
        "targets": {
          "node": "current"
        }
      }
    }
  }
}

Other customization examples

Example: Allow importing modules with an .mjs extension.

{
  "neutrino": {
    "config": {
      "resolve": {
        "extensions": [
          ".mjs"
        ]
      }
    }
  }
}

Advanced configuration

By following the customization guide and knowing the rule, loader, and plugin IDs above, you can override and augment the build by creating a JS module which overrides the config.

Compile targets

This preset uses babel-preset-env to compile code targeting Node.js v6.9+. To change the Node.js target from advanced configuration, specify an object at neutrino.options.compile.targets which contains a babel-preset-env-compatible Node.js target.

Note: Setting these options via neutrino.options.compile must be done prior to loading the TaskCluster preset or they will not be picked up by the compile middleware. These examples show changing compile targets with options before loading the preset and overriding them if loaded afterwards.

Example: Replace the preset Node.js target with support for Node.js 4.2:

module.exports = neutrino => {
  // Using neutrino.options prior to loading TaskCluster preset
  neutrino.options.compile = {
    targets: {
      node: 4.2
    }
  };

  // Using compile options override following loading TaskCluster preset
  neutrino.config.module
    .rule('compile')
    .use('babel')
    .tap(options => {
      options.presets[0][1].targets.node = 4.2;

      return options;
    });
};

Example: Change support to current Node.js version:

module.exports = neutrino => {
  // Using neutrino.options prior to loading TaskCluster preset
  neutrino.options.compile = {
    targets: {
      node: 4.2
    }
  };

  // Using compile options override following loading TaskCluster preset
  neutrino.config.module
    .rule('compile')
    .use('babel')
    .tap(options => {
      options.presets[0][1].targets.node = 'current';

      return options;
    });
};

Other customization examples

Example: Allow importing modules with an .mjs extension.

module.exports = neutrino => {
  neutrino.config.resolve.extensions.add('.mjs');
};