@embroider/macros

What is @embroider/macros?

@embroider/macros is a package designed for use with the Embroider build system for Ember.js applications. It provides a set of macros that allow developers to write conditional code that can be optimized away at build time, enabling features like dead code elimination and environment-specific code paths.

What are @embroider/macros's main functionalities?

Environment-Specific Code

This feature allows you to write code that only runs in specific environments, such as production or development. The `macroCondition` and `getOwnConfig` functions are used to determine the environment and conditionally execute code.

import { macroCondition, getOwnConfig } from '@embroider/macros';

if (macroCondition(getOwnConfig().isProduction)) {
  console.log('This code runs only in production');
} else {
  console.log('This code runs in development');
}

Dead Code Elimination

This feature allows you to write code that is only included in the build if certain conditions are met, such as the presence of a specific dependency version. This can help reduce the size of your final build by eliminating unnecessary code.

import { macroCondition, dependencySatisfies } from '@embroider/macros';

if (macroCondition(dependencySatisfies('ember-source', '>=3.20.0'))) {
  console.log('This code runs only if ember-source version is 3.20.0 or higher');
}

Static Configuration

This feature allows you to access static configuration values at build time. The `getConfig` function retrieves configuration values that can be used in your application code.

import { getConfig } from '@embroider/macros';

const config = getConfig();
console.log(`API endpoint: ${config.apiEndpoint}`);

Other packages similar to @embroider/macros

babel-plugin-macros

babel-plugin-macros is a Babel plugin that allows you to create compile-time code transformations using macros. It provides similar functionality to @embroider/macros by enabling conditional code and static configuration, but it is not specific to Ember.js and can be used with any JavaScript project.

webpack

Webpack is a popular module bundler for JavaScript applications. It provides features like environment-specific code and dead code elimination through plugins and configuration options. While it is more general-purpose and not specific to Ember.js, it can achieve similar results to @embroider/macros with the right setup.

rollup

Rollup is a module bundler for JavaScript that focuses on creating smaller and faster bundles. It offers features like tree-shaking (dead code elimination) and can be configured to handle environment-specific code. Like webpack, it is not specific to Ember.js but can be used to achieve similar goals.

README

@embroider/macros

A standardized solution for modifying your package's Javascript and Glimmer templates at app-compilation-time.

Motivation

Traditionally, Ember addons have a lot of power to run arbitrary code during the build process. This lets them do whatever they need to do, but it also makes them hard to statically analyze and makes them play badly with some tooling (like IDEs).

The Embroider package spec proposes fixing this by making Ember addons much more static. But they will still need the ability to change themselves in certain ways at app compilation time. Hence this package.

This package works in both Embroider and Classical builds, so that addon authors can switch to this newer pattern without disruption.

Setting Configuration: from an Ember app

1. Add @embroider/macros as devDependency.
2. In ember-cli-build.js, do:

let app = new EmberApp(defaults, {
  '@embroider/macros': {
    // this is how you configure your own package
    setOwnConfig: {
      // your config goes here
    },
    // this is how you can optionally send configuration into your
    // dependencies, if those dependencies choose to use
    // @embroider/macros configs.
    setConfig: {
      'some-dependency': {
        // config for some-dependency
      },
    },
  },
});

Setting Configuration: from an Ember Addon

1. Add @embroider/macros as dependency.
2. In index.js, do:

module.exports = {
  name: require('./package').name,
  options: {
    '@embroider/macros': {
      setOwnConfig: {
        // your config goes here
      },
      setConfig: {
        'some-dependency': {
          // config for some-dependency
        },
      },
    },
  },
};

The Macros

macroCondition

The macroCondition macro allows branch level code isolation (and deletion in the case of production builds). Generally macroConditions are viewed as a foundation macro and are combined with others marcos (detailed below) to create more complex scenarios. macroCondition takes a single argument which must be statically known or another macro which will compile down to a static value.

import { macroCondition } from '@embroider/macros';

if (macroCondition(true)) {
  // this branch will remain in both dev and production builds
} else if (macroCondition(false)) {
  // this branch will never be hit and furthermore in production
  // builds it will be fully removed
}

// they can also be used as ternary expressions:
let specialVariable = 'Hello ' + (macroCondition(true) ? 'Bob' : 'Jane');

console.log(specialVariable); // will print "Hello Bob"

Macros can also be used inside of templates:

{{#if (macroCondition true)}}
  red
{{else}}
  blue
{{/if}}

import { macroCondition } from '@embroider/macros';

let foo = true;
if (macroCondition(foo)) {
  // this is not allowed as the first argument must be statically known
}

importSync

The primary reason for Embroider's existence is to create statically analyzable builds. An under pinning of this is the ability to walk and understand the dependency graph of every module. Embroider can natively understand imports such as import foo as 'foo' but cannot handle require's (imagine: require(bar ? 'bar' : 'baz'). The importSync macro is way to "tell" Embroider about the existence of a module and to bring it into a package's scope such that it can be discovered and included into the final build. importSync takes a single static string as its only required argument.

import { importSync } from '@embroider/macros';

let foo = importSync('foo');

// will compile to:

let foo = require('foo');

dependencySatisfies

Tests whether a given dependency is present and satisfies the given semver range. Both arguments must be strings and the second argument will be passed into semver's satisfies method.

import { dependencySatisfies } from '@embroider/macros';

let doesFooExist = dependencySatisfies('foo', '1.0.0');

// will compile to:

let doesFooExist = true; // or false if the dependency was not satisfied

We can use this macro along with the macroCondition and importSync macro's from above to do something more complex:

import { macroCondition, dependencySatisfies, importSync } from '@embroider/macros';

if (macroCondition(dependencySatisfies('ember-qunit', '*'))) {
  return importSync('ember-qunit');
} else if (macroCondition(dependencySatisfies('ember-mocha', '*'))) {
  return importSync('ember-mocha');
}

{{macroDependencySatisfies 'qunit' '^2.8.0'}}

getOwnConfig, getConfig, and getGlobalConfig

A common pattern is to have a set of configuration properties that you define (or a consumer defines for you) which you base certain build time conditions around. This is achieved via the getOwnConfig, getConfig, and getGlobalConfig macros (depending on which config you want to read).

module.exports = {
  name: require('./package').name,
  options: {
    '@embroider/macros': {
      setOwnConfig: {
        themeColor: 'red',
      },
    },
  },
  included() {
    this._super.included.apply(this, arguments);
    this.options['@embroider/macros'].setOwnConfig.shouldIncludeMinifiedLibrary = false;
  },
};

import { getOwnConfig, importSync, macroCondition } from '@embroider/macros';

if (macroCondition(getOwnConfig().shouldIncludeMinifiedLibrary)) {
  importSync('minified-library');
} else {
  importSync('unminified-library');
}

<button class="{{macroGetOwnConfig "themeColor"}}">My Themed Button</button>

Real world examples

Below are a list of addons that have started using @embroider/macros so that you can get a feel for common use cases that can be solved via the macro system.

• ember-exam
• ember-bootstrap
• ember-stargate

Changelog

0.34.0 (2020-12-09)

• ENHANCEMENT: add publicAssetURL option to @embroider/webpack to support CDN deploys (the built-in webpack options for this didn't let you manipulate your index.html, since we take care of that directly in @embroider/webpack).
• COMPAT: update @embroider/util to follow internal refactoring on ember canary.
• HOUSEKEEPING: broccoli-related dependency updates
• DOCS: split the "Replacing the Component Helper" guide into its own document and expanded the use cases.