Use SWC loader

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    shakapacker (6.0.0.rc.13)
+    shakapacker (6.0.0)
       activesupport (>= 5.2)
       rack-proxy (>= 0.6.1)
       railties (>= 5.2)

README.md

@@ -41,6 +41,7 @@ Discussion forums to discuss debugging and troubleshooting tips. Please open iss
   - [Development](#development)
   - [Webpack Configuration](#webpack-configuration)
   - [Babel configuration](#babel-configuration)
+  - [SWC configuration](#swc-configuration)
   - [Integrations](#integrations)
     - [React](#react)
     - [Typescript](#typescript)
@@ -371,6 +372,12 @@ By default, you will find the Webpacker preset in your `package.json`. Note, you
 
 Optionally, you can change your Babel configuration by removing these lines in your `package.json` and add [a Babel configuration file](https://babeljs.io/docs/en/config-files) in your project. For an example customization based on the original, see [Customizing Babel Config](./docs/customizing_babel_config.md).
 
+### SWC configuration
+
+You can try out experimental integration with the SWC loader. You can read more at [SWC usage docs](./docs/using_swc_loader.md).
+
+Please note that if you want opt-in to use SWC, you can skip [React](#react) integration instructions as it is supported out of the box.
+
 ### Integrations
 
 Webpacker out of the box supports JS and static assets (fonts, images etc.) compilation. To enable support for CoffeeScript or TypeScript install relevant packages:

docs/using_swc_loader.md

@@ -0,0 +1,151 @@
+# Using SWC Loader
+
+:warning: This feature is currently experimental. If you face any issues, please report at https://github.com/shakacode/shakapacker/issues.
+
+## About SWC
+
+[SWC (Speedy Web compiler)](https://swc.rs/) is a Rust-based compilation and bundler tool that can be used for Javascript and Typescript files. It claims to be 20x faster than Babel!
+
+It supports all ECMAScript features and it's designed to be a drop-in replacement for Babel and its plugins. Out of the box, it supports TS, JSX syntax, React fast refresh, and much more.
+
+For comparison between SWC and Babel, see the docs at https://swc.rs/docs/migrating-from-babel.
+
+## Switching your Shakapacker project to SWC
+
+In order to use SWC as your compiler today. You need to do two things:
+
+1. Make sure you've installed `@swc/core` and `swc-loader` packages.
+
+```
+yarn add -D @swc/core swc-loader
+```
+
+2. Add or change `webpacker_loader` value in your default `webpacker.yml` config to `swc`
+The default configuration of babel is done by using `package.json` to use the file within the `shakapacker` package.
+
+```json
+default: &default
+  source_path: app/javascript
+  source_entry_path: /
+  public_root_path: public
+  public_output_path: packs
+  cache_path: tmp/webpacker
+  webpack_compile_output: true
+
+  # Additional paths webpack should look up modules
+  # ['app/assets', 'engine/foo/app/assets']
+  additional_paths: []
+
+  # Reload manifest.json on all requests so we reload latest compiled packs
+  cache_manifest: false
+
+  # Select loader to use, available options are 'babel' (default) or 'swc'
+  webpack_loader: 'swc'
+```
+
+## Usage
+
+### React
+
+React is supported out of the box, provided you use `.jsx` or `.tsx` file extension. Shakapacker config will correctly recognize those and tell SWC to parse the JSX syntax correctly. If you wish to customize the transform options to match any existing `@babel/preset-react` settings, you can do that through customizing loader options as described below. You can see available options at https://swc.rs/docs/configuration/compilation#jsctransformreact.
+
+### Typescript
+
+Typescript is supported out of the box, but certain features like decorators need to be enabled through the custom config. You can see available customizations options at https://swc.rs/docs/configuration/compilation, which you can apply through customizing loader options as described below.
+
+Please note that SWC is not using the settings from `.tsconfig` file. Any non-default settings you might have there will need to be applied to the custom loader config.
+
+## Customizing loader options
+
+You can see the default loader options at [swc/index.js](../package/swc/index.js).
+
+If you wish to customize the loader defaults further, for example, if you want to enable support for decorators or React fast refresh, you need to create a `swc.config.js` file in your app config folder.
+
+This file should have a single default export which is an object with an `options` key. Your customizations will be merged with default loader options. You can use this to override or add additional configurations.
+
+Inside the `options` key, you can use any options available to the SWC compiler. For the options reference, please refer to [official SWC docs](https://swc.rs/docs/configuration/compilation).
+
+See some examples below of potential `config/swc.config.js`.
+
+### Example: Enabling top level await and decorators
+
+
+```js
+const customConfig = {
+  options: {
+    jsc: {
+      parser: {
+        topLevelAwait: true,
+        decorators: true
+      }
+    }
+  }
+}
+
+module.exports = customConfig
+```
+
+### Example: Matching existing `@babel/present-env` config
+
+```js
+const { env } = require('shakapacker')
+
+const customConfig = {
+  options: {
+    jsc: {
+      transform: {
+        react: {
+          development: env.isDevelopment,
+          useBuiltins: true
+        }
+      }
+    }
+  }
+}
+
+module.exports = customConfig
+```
+
+### Example: Enabling React Fast Refresh
+
+:warning: Remember that you still need to add [@pmmmwh/react-refresh-webpack-plugin](https://github.com/pmmmwh/react-refresh-webpack-plugin) to your webpack config. The setting below just replaces equivalent `react-refresh/babel` Babel plugin.
+
+
+```js
+const { env } = require('shakapacker')
+
+const customConfig = {
+  options: {
+    jsc: {
+      transform: {
+        react: {
+          refresh: env.isDevelopment && env.runningWebpackDevServer
+        }
+      }
+    }
+  }
+}
+
+module.exports = customConfig
+```
+
+### Example: Adding browserslist config
+
+```js
+
+const customConfig = {
+  options: {
+    env: {
+      targets: '> 0.25%, not dead'
+    }
+  }
+}
+
+module.exports = customConfig
+```
+
+
+## Known limitations
+
+- `browserslist` config at the moment is not being picked up automatically. [Related SWC issue](https://github.com/swc-project/swc/issues/3365). You can add your browserlist config through customizing loader options as outlined above.
+- Using `.swcrc` config file is currently not supported. You might face some issues when `.swcrc` config is diverging from the SWC options we're passing in the Webpack rule.

lib/install/config/webpacker.yml

@@ -15,6 +15,9 @@ default: &default
   # Reload manifest.json on all requests so we reload latest compiled packs
   cache_manifest: false
 
+  # Select loader to use, available options are 'babel' (default) or 'swc'
+  webpack_loader: 'babel'
+
 development:
   <<: *default
   compile: true

package.json

@@ -39,6 +39,7 @@
     "eslint-plugin-jsx-a11y": "^6.4.1",
     "eslint-plugin-react": "^7.26.0",
     "jest": "^27.2.1",
+    "swc-loader": "^0.1.15",
     "webpack": "^5.53.0",
     "webpack-assets-manifest": "^5.0.6",
     "webpack-merge": "^5.8.0"

package/rules/babel.js

@@ -1,30 +1,32 @@
 const { resolve } = require('path')
 const { realpathSync } = require('fs')
+const { loaderMatches } = require('../utils/helpers')
 
 const {
   source_path: sourcePath,
-  additional_paths: additionalPaths
+  additional_paths: additionalPaths,
+  webpack_loader: webpackLoader
 } = require('../config')
 const { isProduction } = require('../env')
 
-module.exports = {
-  test: /\.(js|jsx|mjs|ts|tsx|coffee)?(\.erb)?$/,
-  include: [sourcePath, ...additionalPaths].map((p) => {
-    try {
-      return realpathSync(p)
-    } catch (e) {
-      return resolve(p)
-    }
-  }),
-  exclude: /node_modules/,
-  use: [
-    {
-      loader: require.resolve('babel-loader'),
-      options: {
-        cacheDirectory: true,
-        cacheCompression: isProduction,
-        compact: isProduction
+module.exports = loaderMatches(webpackLoader, 'babel', () => ({
+    test: /\.(js|jsx|mjs|ts|tsx|coffee)?(\.erb)?$/,
+    include: [sourcePath, ...additionalPaths].map((p) => {
+      try {
+        return realpathSync(p)
+      } catch (e) {
+        return resolve(p)
       }
-    }
-  ]
-}
+    }),
+    exclude: /node_modules/,
+    use: [
+      {
+        loader: require.resolve('babel-loader'),
+        options: {
+          cacheDirectory: true,
+          cacheCompression: isProduction,
+          compact: isProduction
+        }
+      }
+    ]
+  }))

package/rules/index.js

@@ -7,6 +7,7 @@ const rules = {
   css: require('./css'),
   sass: require('./sass'),
   babel: require('./babel'),
+  swc: require('./swc'),
   erb: require('./erb'),
   coffee: require('./coffee'),
   less: require('./less'),

package/rules/swc.js

@@ -0,0 +1,23 @@
+const { resolve } = require('path')
+const { realpathSync } = require('fs')
+const { loaderMatches } = require('../utils/helpers')
+const { getSwcLoaderConfig } = require('../swc')
+
+const {
+  source_path: sourcePath,
+  additional_paths: additionalPaths,
+  webpack_loader: webpackLoader
+} = require('../config')
+
+module.exports = loaderMatches(webpackLoader, 'swc', () => ({
+  test: /\.(ts|tsx|js|jsx|mjs|coffee)?(\.erb)?$/,
+  include: [sourcePath, ...additionalPaths].map((p) => {
+    try {
+      return realpathSync(p)
+    } catch (e) {
+      return resolve(p)
+    }
+  }),
+  exclude: /node_modules/,
+  use: ({ resource }) => getSwcLoaderConfig(resource)
+}))

package/swc/index.js

@@ -0,0 +1,50 @@
+/* eslint global-require: 0 */
+/* eslint import/no-dynamic-require: 0 */
+
+const { resolve } = require('path')
+const { existsSync } = require('fs')
+const { merge } = require('webpack-merge')
+
+const isJsxFile = (filename) => !!filename.match(/\.(jsx|tsx)?(\.erb)?$/)
+
+const isTypescriptFile = (filename) => !!filename.match(/\.(ts|tsx)?(\.erb)?$/)
+
+const getCustomConfig = () => {
+  const path = resolve('config', 'swc.config.js')
+  if (existsSync(path)) {
+    return require(path)
+  }
+  return {}
+}
+
+const getSwcLoaderConfig = (filenameToProcess) => {
+  const customConfig = getCustomConfig()
+  const defaultConfig = {
+    loader: require.resolve('swc-loader'),
+    options: {
+      jsc: {
+        parser: {
+          dynamicImport: true,
+          syntax: isTypescriptFile(filenameToProcess)
+            ? 'typescript'
+            : 'ecmascript',
+          [isTypescriptFile(filenameToProcess) ? 'tsx' : 'jsx']:
+            isJsxFile(filenameToProcess)
+        }
+      },
+      sourceMaps: true,
+      env: {
+        coreJs: '3.8',
+        loose: true,
+        exclude: ['transform-typeof-symbol'],
+        mode: 'entry'
+      }
+    }
+  }
+
+  return merge(defaultConfig, customConfig)
+}
+
+module.exports = {
+  getSwcLoaderConfig
+}

package/utils/helpers.js

@@ -27,7 +27,7 @@ const resolvedPath = (packageName) => {
   }
 }
 
-const moduleExists = (packageName) => (!!resolvedPath(packageName))
+const moduleExists = (packageName) => !!resolvedPath(packageName)
 
 const canProcess = (rule, fn) => {
   const modulePath = resolvedPath(rule)
@@ -39,6 +39,22 @@ const canProcess = (rule, fn) => {
   return null
 }
 
+const loaderMatches = (configLoader, loaderToCheck, fn) => {
+  if (configLoader !== loaderToCheck) {
+    return null
+  }
+
+  const loaderName = `${configLoader}-loader`
+
+  if (!moduleExists(loaderName)) {
+    throw new Error(
+      `Your webpacker config specified using ${configLoader}, but ${loaderName} package is not installed. Please install ${loaderName} first.`
+    )
+  }
+
+  return fn()
+}
+
 module.exports = {
   chdirTestApp,
   chdirCwd,
@@ -47,5 +63,6 @@ module.exports = {
   ensureTrailingSlash,
   canProcess,
   moduleExists,
-  resetEnv
+  resetEnv,
+  loaderMatches
 }

test/mounted_app/test/dummy/config/webpacker.yml

@@ -5,6 +5,7 @@ default: &default
   source_entry_path: entrypoints
   public_output_path: packs
   cache_path: tmp/webpacker
+  webpack_loader: babel
 
   # Additional paths webpack should look up modules
   # ['app/assets', 'engine/foo/app/assets']

test/test_app/config/webpacker.yml

@@ -7,6 +7,7 @@ default: &default
   public_output_path: packs
   cache_path: tmp/webpacker
   webpack_compile_output: false
+  webpack_loader: babel
 
   # Additional paths webpack should look up modules
   # ['app/assets', 'engine/foo/app/assets']