# webpackr

**Repository Path**: mirrors_shakacode/webpackr

## Basic Information

- **Project Name**: webpackr
- **Description**: Use Webpack to manage app-like JavaScript modules in Rails
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2022-01-18
- **Last Updated**: 2026-05-17

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Shakapacker (v10)

---

_🚀 Shakapacker 10 supports [Rspack](https://rspack.rs/)! 10x faster than webpack!_

_📖 **Full documentation at [shakapacker.com](https://shakapacker.com)**_

---

_Official, actively maintained successor to [rails/webpacker](https://github.com/rails/webpacker). ShakaCode stands behind the long-term maintenance and development of this project for the Rails community._

- ⚠️ See the [6-stable](https://github.com/shakacode/shakapacker/tree/6-stable) branch for Shakapacker v6.x code and documentation. :warning:
- **See the [v10.0.0 release notes](https://github.com/shakacode/shakapacker/releases/tag/v10.0.0) for upgrading from v9 to v10.**
- **See [V9 Upgrade](./docs/v9_upgrade.md) for upgrading from v8 to v9.**
- See [V8 Upgrade](./docs/v8_upgrade.md) for upgrading from the v7 release.
- See [V7 Upgrade](./docs/v7_upgrade.md) for upgrading from the v6 release.
- See [V6 Upgrade](./docs/v6_upgrade.md) for upgrading from v5 or prior v6 releases.

[![Ruby based checks](https://github.com/shakacode/shakapacker/workflows/Ruby%20based%20checks/badge.svg)](https://github.com/shakacode/shakapacker/actions)
[![Jest specs](https://github.com/shakacode/shakapacker/workflows/Jest%20specs/badge.svg)](https://github.com/shakacode/shakapacker/actions)
[![Rubocop](https://github.com/shakacode/shakapacker/workflows/Rubocop/badge.svg)](https://github.com/shakacode/shakapacker/actions)
[![JS lint](https://github.com/shakacode/shakapacker/workflows/JS%20lint/badge.svg)](https://github.com/shakacode/shakapacker/actions)

[![node.js](https://img.shields.io/badge/node-%3E%3D%2020-brightgreen.svg)](https://www.npmjs.com/package/shakapacker)
[![Gem](https://img.shields.io/gem/v/shakapacker.svg)](https://rubygems.org/gems/shakapacker)
[![npm version](https://badge.fury.io/js/shakapacker.svg)](https://badge.fury.io/js/shakapacker)

Shakapacker makes it easy to use the JavaScript pre-processor and bundler [Webpack v5+](https://webpack.js.org/)
to manage frontend JavaScript in Rails. It can coexist with the asset pipeline,
leaving Webpack responsible solely for frontend JavaScript, or can be used exclusively, making it also responsible for images, fonts, and CSS.

Check out 6.1.1+ for [SWC](https://swc.rs/) and [esbuild-loader](https://github.com/privatenumber/esbuild-loader) support! They are faster than Babel!

See a comparison of [Shakapacker with jsbundling-rails](https://github.com/rails/jsbundling-rails/blob/main/docs/comparison_with_webpacker.md). For an in-depth discussion of choosing between `shakapacker` and `jsbundling-rails`, see the discussion [Webpacker alternatives - which path should we go to? #8783](https://github.com/decidim/decidim/discussions/8783) and the resulting PR [Switch away from Webpacker to Shakapacker #10389](https://github.com/decidim/decidim/pull/10389).

For discussions, see our [Slack Channel](https://reactrails.slack.com/join/shared_invite/enQtNjY3NTczMjczNzYxLTlmYjdiZmY3MTVlMzU2YWE0OWM0MzNiZDI0MzdkZGFiZTFkYTFkOGVjODBmOWEyYWQ3MzA2NGE1YWJjNmVlMGE).

---

## ShakaCode Support

[ShakaCode](https://www.shakacode.com) focuses on helping Ruby on Rails teams use React and Webpack better. We can upgrade your project and improve your development and customer experiences, allowing you to focus on building new features or fixing bugs instead.

For an overview of working with us, see our [Client Engagement Model](https://www.shakacode.com/blog/client-engagement-model/) article and [how we bill for time](https://www.shakacode.com/blog/shortcut-jira-trello-github-toggl-time-and-task-tracking/).

We also specialize in helping development teams lower infrastructure and CI costs. Check out our project [Control Plane Flow](https://github.com/shakacode/control-plane-flow/), which can allow you to get the ease of Heroku with the power of Kubernetes and big cost savings.

If you think ShakaCode can help your project, [click here](https://meetings.hubspot.com/justingordon/30-minute-consultation) to book a call with [Justin Gordon](mailto:justin@shakacode.com), the creator of React on Rails and Shakapacker.

Here's a testimonial of how ShakaCode can help from [Florian Gößler](https://github.com/FGoessler) of [Blinkist](https://www.blinkist.com/), January 2, 2023:

> Hey Justin 👋
>
> I just wanted to let you know that we today shipped the webpacker to shakapacker upgrades and it all seems to be running smoothly! Thanks again for all your support and your teams work! 😍
>
> On top of your work, it was now also very easy for me to upgrade Tailwind and include our external node_module based web component library which we were using for our other (more modern) apps already. That work is going to be shipped later this week though as we are polishing the last bits of it. 😉
>
> Have a great 2023 and maybe we get to work together again later in the year! 🙌

Read the [full review here](https://clutch.co/profile/shakacode#reviews?sort_by=date_DESC#review-2118154).

Here's a testimonial from Jon Rajavuori of [Academia.edu](https://www.academia.edu/) about migrating frontend builds from Webpack to [rspack](https://rspack.rs/) with ShakaCode's help, shared in March 2026:

> We've been running [rspack](https://rspack.rs/) most of the week now for frontend builds! It's a performance-focused drop-in replacement for Webpack that apparently works as advertised. The impact has been between a **2-4x build speed increase** depending on the environment and conditions.
>
> The typical case of first startup with a warm cache has gone from roughly 1m with Webpack down to about **20s** — close to the amount of time other dev components take to startup.
>
> As for production **incremental** builds, they now take around 10s when only a few lines in one bundle have changed!
>
> Additional stats from follow-up conversation with Jon:
>
> - Cold-cache startup: **4m30s → 3m30s** (~22% faster; 2-4x gains apply to warm-cache and incremental builds)
> - Production incremental builds: **~10 seconds**
> - HMR rebuild time: unchanged at ~8s (bottleneck is orchestration, not compilation)

---

<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->

- [Prerequisites](#prerequisites)
- [Features](#features)
  - [Optional support](#optional-support)
- [Installation](#installation)
  - [Rails v6+](#rails-v6)
- [Concepts](#concepts)
- [Usage](#usage)
  - [Configuration and Code](#configuration-and-code)
    - [Configuration Guide](./docs/configuration.md)
  - [View Helpers](#view-helpers)
    - [View Helpers `javascript_pack_tag` and `stylesheet_pack_tag`](#view-helpers-javascript_pack_tag-and-stylesheet_pack_tag)
    - [View Helpers `append_javascript_pack_tag`, `prepend_javascript_pack_tag` and `append_stylesheet_pack_tag`](#view-helper-append_javascript_pack_tag-prepend_javascript_pack_tag-and-append_stylesheet_pack_tag)
    - [View Helper: `asset_pack_path`](#view-helper-asset_pack_path)
    - [View Helper: `image_pack_tag`](#view-helper-image_pack_tag)
    - [View Helper: `favicon_pack_tag`](#view-helper-favicon_pack_tag)
    - [View Helper: `preload_pack_asset`](#view-helper-preload_pack_asset)
    - [HTTP 103 Early Hints](#http-103-early-hints)
  - [Images in Stylesheets](#images-in-stylesheets)
  - [Server-Side Rendering (SSR)](#server-side-rendering-ssr)
  - [Development](#development)
    - [Automatic Webpack Code Building](#automatic-webpack-code-building)
    - [Compiler strategies](#compiler-strategies)
    - [Common Development Commands](#common-development-commands)
  - [Ruby API Reference](#ruby-api-reference)
  - [Webpack Configuration](#webpack-configuration)
  - [Babel configuration](#babel-configuration)
  - [SWC configuration](#swc-configuration)
  - [esbuild loader configuration](#esbuild-loader-configuration)
  - [Integrations](#integrations)
    - [React](#react)
    - [Typescript](#typescript)
    - [CSS](#css)
    - [Postcss](#postcss)
    - [Sass](#sass)
    - [Less](#less)
    - [Stylus](#stylus)
    - [CoffeeScript](#coffeescript)
    - [Other frameworks](#other-frameworks)
  - [Custom Rails environments](#custom-rails-environments)
  - [Upgrading](#upgrading)
  - [Paths](#paths)
  - [Additional paths](#additional-paths)
- [Deployment](#deployment)
- [Example Apps](#example-apps)
- [Troubleshooting](#troubleshooting)
- [Contributing](#contributing)
- [License](#license)
- [Supporters](#supporters)

<!-- END doctoc generated TOC please keep comment here to allow auto update -->

## Prerequisites

- Ruby 2.7+
- Rails 5.2+
- Node.js 20+

## Features

- Rails view helpers that fully support Webpack output, including HMR and code splitting.
- Convenient but not required webpack configuration. The only requirement is that your webpack configuration creates a manifest.
- HMR with the `shakapacker-dev-server`, such as for hot-reloading React!
- Automatic code splitting using multiple entry points to optimize JavaScript downloads.
- Support for [NPM](https://www.npmjs.com/package/npm), Yarn ([classic](https://classic.yarnpkg.com/lang/en/) and [berry](https://yarnpkg.com/getting-started)), [PNPM](https://pnpm.io/), and [Bun](https://bun.sh/)
- [Webpack v5+](https://webpack.js.org/)
- ES6 with [babel](https://babeljs.io/), [SWC](https://swc.rs/), or [Esbuild](https://github.com/privatenumber/esbuild-loader)
- Asset compression, source-maps, and minification
- CDN support
- Extensible and configurable. For example, all major dependencies are specified as peers, so you can upgrade easily.

### Optional support

_Requires extra packages to be installed._

- React
- TypeScript
- Stylesheets - Sass, Less, Stylus and Css, PostCSS
- CoffeeScript

## Installation

### Rails v6+

With Rails v6+, skip JavaScript for a new app and follow below Manual Installation Steps to manually add the `shakapacker` gem to your Gemfile.

```bash
rails new myapp --skip-javascript
```

_Note, Rails 6 installs the older v5 version of webpacker unless you specify `--skip-javascript`._

Add `shakapacker` gem to your `Gemfile`:

```bash
bundle add shakapacker --strict
```

Then run the following to install Shakapacker:

```bash
./bin/bundle install
bundle exec rake shakapacker:install
```

Before initiating the installation process, ensure you have committed all changes. During install, Shakapacker may encounter conflicts with existing files. You can approve prompts interactively, use `FORCE=true` to overwrite without prompting, or use `SKIP=true` to preserve existing files and only create missing ones. Accepted truthy values are `true`, `1`, and `yes` (case-insensitive). If both are set, `FORCE` takes precedence.

Shakapacker uses the [`package_json`](https://github.com/shakacode/package_json) gem to handle updating the `package.json` and interacting with the underlying package manager of choice for managing dependencies and running commands; the package manager is managed using the [`packageManager`](https://nodejs.org/api/packages.html#packagemanager) property in the `package.json`, otherwise falling back to the value of `PACKAGE_JSON_FALLBACK_MANAGER` if set or otherwise `npm`.

If `packageManager` is not set when running `shakapacker:install`, Shakapacker will set it based on the lockfile and the result of calling `--version` on the inferred manager; if no lockfile is present, then `npm` be used unless you choose to explicitly set the `PACKAGE_JSON_FALLBACK_MANAGER` to your preferred package manager.

> [!NOTE]
>
> The `packageManager` property is only used to determine the package manager to use, based primarily on its name.
> The version (if present) is only used to determine if Yarn Classic or Yarn Berry should be used, but is otherwise
> _not_ checked, nor is [`corepack`](https://nodejs.org/api/corepack.html) used to ensure that the package manager is installed.
>
> It is up to the developer to ensure that the desired package manager is actually install at the right version, which can be done
> using `corepack` or by other means.

See [here](https://github.com/G-Rath/package_json#specifying-a-package-manager) for a list of the supported package managers and more information; note that `package_json` does not handle ensuring the manager is installed.

If you wish to use [Yarn PnP](https://yarnpkg.com/features/pnp) you will need to configure Babel using a `babel.config.js` file rather than via `package.json` - see [customizing Babel Config](./docs/customizing_babel_config.md) for examples on how to do this.

> [!NOTE]
>
> The rest of the documentation will only reference `npm` when providing commands such as to install optional packages except in cases where
> a particular package manager requires a very different command; otherwise it should be safe to just replace `npm` with the name of your
> preferred package manager when running the command

Note, in v6+, most JS packages are peer dependencies. During `shakapacker:install`, Shakapacker
adds the subset required for your chosen bundler/transpiler setup rather than forcing every
supported package into every app.

See:

- [Optional Peer Dependencies](./docs/optional-peer-dependencies.md) for how optional peers work
- [Shakapacker's Peer Dependencies](./docs/peer-dependencies.md) for the current supported version ranges

This keeps installation flexible while still making the supported dependency ranges explicit.

### Optional Peer Dependencies

All peer dependencies in Shakapacker are marked as optional via `peerDependenciesMeta`. This design decision ensures:

- **No warnings during package installation** when dependencies are not needed
- **Clear visibility of supported package versions** for upgrades
- **Flexibility to choose only the tools you need** (webpack vs rspack, babel vs swc vs esbuild)

The optional peer dependencies approach means you only install what you actually use, while still maintaining
version compatibility constraints when you do install those packages.

#### Required Dependencies by Configuration

Depending on your setup, you'll need different subsets of the optional peer dependencies:

**For Webpack + Babel (traditional setup):**

```json
{
  "dependencies": {
    "shakapacker": "^10.0.0",
    "@babel/core": "^7.17.9",
    "@babel/plugin-transform-runtime": "^7.17.0",
    "@babel/preset-env": "^7.16.11",
    "@babel/runtime": "^7.17.9",
    "babel-loader": "^8.2.4",
    "compression-webpack-plugin": "^9.0.0",
    "terser-webpack-plugin": "^5.3.1",
    "webpack": "^5.101.0",
    "webpack-assets-manifest": "^5.0.6",
    "webpack-cli": "^6.0.0",
    "webpack-dev-server": "^5.2.2"
  }
}
```

> **Note:** `webpack-cli` v7 is also supported but requires Node.js >= 20.9.0. If you're on Node >= 20.9.0, you can use `"webpack-cli": "^7.0.0"` instead. See [peer-dependencies.md](./docs/peer-dependencies.md) for the full supported range.

**For Webpack + SWC (faster alternative):**

```json
{
  "dependencies": {
    "shakapacker": "^10.0.0",
    "@swc/core": "^1.3.0",
    "swc-loader": "^0.2.0",
    "compression-webpack-plugin": "^9.0.0",
    "terser-webpack-plugin": "^5.3.1",
    "webpack": "^5.101.0",
    "webpack-assets-manifest": "^5.0.6",
    "webpack-cli": "^6.0.0",
    "webpack-dev-server": "^5.2.2"
  }
}
```

**For Rspack + SWC (10x faster bundling):**

```json
{
  "dependencies": {
    "shakapacker": "^10.0.0",
    "@rspack/core": "^2.0.0-0",
    "@rspack/cli": "^2.0.0-0",
    "@swc/core": "^1.3.0",
    "swc-loader": "^0.2.0",
    "rspack-manifest-plugin": "^5.0.0"
  }
}
```

**Quick tip:** You can easily switch between webpack and rspack using:

```bash
bundle exec rake shakapacker:switch_bundler rspack -- --install-deps

# For faster switching, use --no-uninstall to keep both bundlers installed
bundle exec rake shakapacker:switch_bundler webpack -- --install-deps --no-uninstall
```

See the [Rspack Migration Guide](./docs/rspack_migration_guide.md) for details.

**For CSS/Sass processing (add to any config above):**

```json
{
  "dependencies": {
    "css-loader": "^6.8.1",
    "mini-css-extract-plugin": "^2.0.0",
    "sass": "^1.50.0",
    "sass-loader": "^13.0.0"
  }
}
```

## Concepts

At its core, Shakapacker's essential function is to:

1. Provide configuration by a single file used by both Rails view helpers and JavaScript webpack compilation code.
2. Provide Rails view helpers, utilizing this configuration file so that a webpage can load JavaScript, CSS, and other static assets compiled by webpack, supporting bundle splitting, fingerprinting, and HMR.
3. Provide a community-supported, default webpack compilation that generates the necessary bundles and manifest, using the same configuration file. This compilation can be extended for any needs.

## Usage

### Configuration and Code

**📖 For a comprehensive guide to all configuration options, see the [Configuration Guide](./docs/configuration.md)**

**📦 For Node package exports and config object docs, see the [Node Package API Guide](./docs/node_package_api.md)**

This includes documentation for:

- All `config/shakapacker.yml` options (including `assets_bundler_config_path`)
- Environment-specific configuration
- Development server settings
- Build configurations (`config/shakapacker-builds.yml`)
- Best practices and common patterns

You will need your file system to correspond to the setup of your `config/shakapacker.yml` file.

Suppose you have the following configuration:

`shakapacker.yml`

```yml
default: &default
  source_path: app/javascript
  source_entry_path: packs
  public_root_path: public
  public_output_path: packs
  nested_entries: false
# And more
```

And that maps to a directory structure like this:

```
app/javascript:
  └── packs:               # sets up webpack entries
  │   └── application.js   # references ../src/my_component.js
  │   └── application.css
  └── src:                 # any directory name is fine. Referenced files need to be under source_path
  │   └── my_component.js
  └── stylesheets:
  │   └── my_styles.css
  └── images:
      └── logo.svg
public/packs                # webpack output
```

Webpack intelligently includes only necessary files. In this example, the file `packs/application.js` would reference `../src/my_component.js`

The `nested_entries` option allows webpack entry points in subdirectories (defaults to `true`). See the [Configuration Guide](./docs/configuration.md#nested_entries) for details.

The `useContentHash` option enables content-based cache busting. It's disabled by default (except in production) to speed up development builds. See the [Configuration Guide](./docs/configuration.md#usecontenthash) for details.

#### Precompile Hook

Shakapacker supports running custom commands before compilation via the `precompile_hook` configuration option.

For configuration details, see [precompile_hook in the Configuration Guide](./docs/configuration.md#precompile_hook).
For complete usage guide, see the [Precompile Hook Guide](./docs/precompile_hook.md).

#### Setting custom config path

You can use the `SHAKAPACKER_CONFIG` environment variable to specify a custom config file path. See [Environment Variables in the Configuration Guide](./docs/configuration.md#environment-variables) for this and other configuration options.

### View Helpers

The Shakapacker view helpers generate the script and link tags to get the webpack output onto your views.

Be sure to consult the API documentation in the source code of [helper.rb](./lib/shakapacker/helper.rb).

**Note:** For your styles or static assets files to be available in your view, you would need to link them in your "pack" or entry file. Otherwise, Webpack won't know to package up those files.

#### View Helpers `javascript_pack_tag` and `stylesheet_pack_tag`

These view helpers take your `shakapacker.yml` configuration file and the resulting webpack compilation `manifest.json` and generate the HTML to load the assets.

You can then link the JavaScript pack in Rails views using the `javascript_pack_tag` helper. If you have styles imported in your pack file, you can link them by using `stylesheet_pack_tag`:

```erb
<%= javascript_pack_tag 'application' %>
<%= stylesheet_pack_tag 'application' %>
```

The `javascript_pack_tag` and `stylesheet_pack_tag` helpers will include all the transpiled
packs with the chunks in your view, which creates HTML tags for all the chunks.

You can provide multiple packs and other attributes. Note, `defer` defaults to showing.

```erb
<%= javascript_pack_tag 'calendar', 'map', 'data-turbo-track': 'reload' %>
```

The resulting HTML would look like this:

```html
<script src="/packs/vendor-16838bab065ae1e314.js" data-turbo-track="reload" defer></script>
<script src="/packs/calendar~runtime-16838bab065ae1e314.js" data-turbo-track="reload" defer></script>
<script src="/packs/calendar-1016838bab065ae1e314.js" data-turbo-track="reload" defer"></script>
<script src="/packs/map~runtime-16838bab065ae1e314.js" data-turbo-track="reload" defer></script>
<script src="/packs/map-16838bab065ae1e314.js" data-turbo-track="reload" defer></script>
```

In this output, both the calendar and map codes might refer to other common libraries. Those get placed in something like the vendor bundle. The view helper removes any duplication.

Note, the default of "defer" for the `javascript_pack_tag`. You can override that to `false`. If you expose jquery globally with `expose-loader,` by using `import $ from "expose-loader?exposes=$,jQuery!jquery"` in your `app/javascript/application.js`, pass the option `defer: false` to your `javascript_pack_tag`.

The `javascript_pack_tag` also supports the `async` attribute, which you can enable by passing `async: true`:

```erb
<%= javascript_pack_tag 'application', async: true %>
```

This will generate script tags with the `async` attribute, which allows the browser to download and execute the script asynchronously without blocking HTML parsing:

```html
<script src="/packs/vendor-16838bab065ae1e314.js" async></script>
<script src="/packs/application~runtime-16838bab065ae1e314.js" async></script>
<script src="/packs/application-1016838bab065ae1e314.js" async></script>
```

Note that when using `async: true`, scripts may execute in any order as soon as they're downloaded, which could cause issues if your code has dependencies between files. In most cases, `defer` (the default) is preferred as it maintains execution order.

> [!NOTE]
>
> When both `async` and `defer` attributes are specified, `async` takes precedence according to HTML5 specifications. So if you pass both `async: true` and `defer: true`, the script tag will use `async`.

**Important:** Pass all your pack names as multiple arguments, not multiple calls, when using `javascript_pack_tag` and the `stylesheet_pack_tag`. Otherwise, you will get duplicated chunks on the page.

```erb
<%# DO %>
<%= javascript_pack_tag 'calendar', 'map' %>

<%# DON'T %>
<%= javascript_pack_tag 'calendar' %>
<%= javascript_pack_tag 'map' %>
```

While this also generally applies to `stylesheet_pack_tag`,
you may use multiple calls to stylesheet_pack_tag if,
say,
you require multiple `<style>` tags for different output media:

```erb
<%= stylesheet_pack_tag 'application', media: 'screen' %>
<%= stylesheet_pack_tag 'print', media: 'print' %>
```

#### View Helper `append_javascript_pack_tag`, `prepend_javascript_pack_tag` and `append_stylesheet_pack_tag`

If you need to configure your script pack names or stylesheet pack names from the view for a route or partials, then you will need some logic to ensure you call the helpers only once with multiple arguments. The new view helpers, `append_javascript_pack_tag` and `append_stylesheet_pack_tag` can solve this problem. The helper `append_javascript_pack_tag` will queue up script packs when the `javascript_pack_tag` is finally used. Similarly,`append_stylesheet_pack_tag` will queue up style packs when the `stylesheet_pack_tag` is finally used.

Main view:

```erb
<% append_javascript_pack_tag 'calendar' %>
<% append_stylesheet_pack_tag 'calendar' %>
```

Some partial:

```erb
<% append_javascript_pack_tag 'map' %>
<% append_stylesheet_pack_tag 'map' %>
```

And the main layout has:

```erb
<%= javascript_pack_tag 'application' %>
<%= stylesheet_pack_tag 'application' %>
```

is the same as using this in the main layout:

```erb
<%= javascript_pack_tag 'calendar', 'map', 'application' %>
<%= stylesheet_pack_tag 'calendar', 'map', 'application' %>
```

However, you typically can't do that in the main layout, as the view and partial codes will depend on the route.

Thus, you can distribute the logic of what packs are needed for any route. All the magic of splitting up the code and CSS was automatic!

**Important:** These helpers can be used anywhere in your application as long as they are executed BEFORE `(javascript/stylesheet)_pack_tag` respectively. If you attempt to call one of these helpers after the respective `(javascript/stylesheet)_pack_tag`, an error will be raised.

The typical issue is that your layout might reference some partials that need to configure packs. A good way to solve this problem is to use `content_for` to ensure that the code to render your partial comes before the call to `javascript_pack_tag`.

```erb
<% content_for :footer do %>
  <%= render 'shared/footer' %>
<% end %>

<%= javascript_pack_tag %>

<%= yield :footer %>
```

There is also `prepend_javascript_pack_tag` that will put the entry at the front of the queue. This is handy when you want an entry in the main layout to go before the partial and main layout `append_javascript_pack_tag` entries.

Main view:

```erb
<% append_javascript_pack_tag 'map' %>
```

Some partial:

```erb
<% append_javascript_pack_tag 'map' %>
```

And the main layout has:

```erb
<% prepend_javascript_pack_tag 'main' %>
<%= javascript_pack_tag 'application' %>
```

is the same as using this in the main layout:

```erb
<%= javascript_pack_tag 'main', 'calendar', 'map', 'application' %>
```

For alternative options for setting the additional packs, [see this discussion](https://github.com/shakacode/shakapacker/issues/39).

**Important:** To prevent FOUC (Flash of Unstyled Content), always place `stylesheet_pack_tag` in the `<head>` section of your layout. When using `append_*` helpers with dynamic pack loading (e.g., React on Rails), use the `content_for` pattern to control execution order. See the [Preventing FOUC guide](./docs/preventing_fouc.md) for detailed examples.

#### View Helper: `asset_pack_path`

If you want to link a static asset for `<img />` tag, you can use the `asset_pack_path` helper:

```erb
<img src="<%= asset_pack_path 'static/logo.svg' %>" />
```

#### View Helper: `image_pack_tag`

Or use the dedicated helper:

```erb
<%= image_pack_tag 'application.png', size: '16x10', alt: 'Edit Entry' %>
<%= image_pack_tag 'picture.png', srcset: { 'picture-2x.png' => '2x' } %>
```

#### View Helper: `favicon_pack_tag`

If you want to create a favicon:

```erb
<%= favicon_pack_tag 'mb-icon.png', rel: 'apple-touch-icon', type: 'image/png' %>
```

#### View Helper: `preload_pack_asset`

If you want to preload a static asset in your `<head>`, you can use the `preload_pack_asset` helper:

```erb
<%= preload_pack_asset 'fonts/fa-regular-400.woff2' %>
```

#### HTTP 103 Early Hints

Automatically send early hints to browsers for faster asset loading. Supports `preload`/`prefetch`/`none` configuration per-page.

```yaml
# config/shakapacker.yml
production:
  early_hints:
    enabled: true
    debug: false # Enable to see what hints are sent (as HTML comments)
```

⚠️ **Important**: May improve or hurt performance depending on content. See the [Early Hints Guide](./docs/early_hints.md) for configuration, performance guidance, and examples.

**Troubleshooting**: Enable `debug: true` to see HTML comments showing what hints were sent or why they were skipped.

**Requirements:** Rails 5.2+, HTTP/2 server, modern browsers. Gracefully degrades if not supported.

### Images in Stylesheets

If you want to use images in your stylesheets:

```css
.foo {
  background-image: url("../images/logo.svg");
}
```

### Server-Side Rendering (SSR)

Note, if you are using server-side rendering of JavaScript with dynamic code-splitting, as is often done with extensions to Shakapacker, like [React on Rails](https://github.com/shakacode/react_on_rails), your JavaScript should create the link prefetch HTML tags that you will use, so you won't need to use to `asset_pack_path` in those circumstances.

### Development

Shakapacker ships with three binstubs: `./bin/shakapacker`, `./bin/shakapacker-dev-server`, and `./bin/shakapacker-watch`. The first two are thin wrappers around the standard `webpack.js` and `webpack-dev-server.js` executables to ensure that the right configuration files and environmental variables are loaded based on your environment. `./bin/shakapacker-watch` is a shell wrapper around `./bin/shakapacker` that traps INT/TERM signals for clean shutdown — use it in Procfile-based workflows (e.g., `foreman`, `bin/dev`) to avoid Ruby interrupt backtraces when pressing Ctrl-C.

_Note: older Shakapacker installations had set a missing NODE_ENV in the binstubs. Please remove this for versions 6.5.2 and newer._

#### Automatic Webpack Code Building

Shakapacker can be configured to automatically compile on demand when needed using `compile` option in the `shakapacker.yml`. This happens when you refer to any of the pack assets using the Shakapacker helper methods. This means that you don't have to run any separate processes. Compilation errors are logged to the standard Rails log. However, this auto-compilation happens when a web request is made that requires an updated webpack build, not when files change. Thus, that can be **painfully slow** for front-end development in this default way. Instead, you should either run the `bin/shakapacker --watch` or run `./bin/shakapacker-dev-server` during development.

The `compile: true` option can be more useful for test and production builds.

#### Compiler strategies

Shakapacker ships with two different strategies that are used to determine whether assets need recompilation per the `compile: true` option:

- `digest` - This strategy calculates SHA1 digest of files in your watched paths (see below). The calculated digest is then stored in a temp file. To check whether the assets need to be recompiled, Shakapacker calculates the SHA1 of the watched files and compares it with the one stored. If the digests are equal, no recompilation occurs. If the digests are different or the temp file is missing, files are recompiled.
- `mtime` - This strategy looks at the last "modified at" timestamps of both files AND directories in your watched paths. The timestamp of the most recent file or directory is then compared with the timestamp of `manifest.json` file generated. If the manifest file timestamp is newer than one of the most recently modified files or directories in the watched paths, no recompilation occurs. If the manifest file is older, files are recompiled.

The `compiler_strategy` option determines how Shakapacker checks if assets need recompilation (`mtime` for development, `digest` for production). See the [Configuration Guide](./docs/configuration.md#compiler_strategy) for detailed comparison and recommendations.

> [!NOTE]
>
> If you are not using the `shakapacker-dev-server`, your packs will be served by the Rails public file server.
> If you've enabled caching (Rails application `config.action_controller.perform_caching` setting),
> your changes will likely not be picked up due to `Cache-Control` header being set and assets being cached in the browser memory.
>
> For more details see [issue 88: Caching issues in Development since migrating to Shakapacker](https://github.com/shakacode/shakapacker/issues/88).

If you want to use live code reloading, or you have enough JavaScript that on-demand compilation is too slow, you'll need to run `./bin/shakapacker-dev-server`. This process will watch for changes in the relevant files, defined by `shakapacker.yml` configuration settings for `source_path`, `source_entry_path`, and `additional_paths`, and it will then automatically reload the browser to match. This feature is also known as [Hot Module Replacement](https://webpack.js.org/concepts/hot-module-replacement/).

#### Common Development Commands

```bash
# webpack dev server
./bin/shakapacker-dev-server

# watcher (use in Procfiles for clean Ctrl-C shutdown)
./bin/shakapacker-watch --watch --progress

# watcher (standalone, without signal handling)
./bin/shakapacker --watch --progress

# standalone build
./bin/shakapacker --progress
```

Once you start this webpack development server, Shakapacker will automatically start proxying all webpack asset requests to this server. When you stop this server, Rails will detect that it's not running and Rails will revert back to on-demand compilation _if_ you have the `compile` option set to true in your `config/shakapacker.yml`

You can use environment variables as options supported by [webpack-dev-server](https://webpack.js.org/configuration/dev-server/) in the form `SHAKAPACKER_DEV_SERVER_<OPTION>`. Please note that these environmental variables will always take precedence over the ones already set in the configuration file, and that the _same_ environmental variables must be available to the `rails server` process.

```bash
SHAKAPACKER_DEV_SERVER_PORT=4305 SHAKAPACKER_DEV_SERVER_HOST=example.com SHAKAPACKER_DEV_SERVER_INLINE=true SHAKAPACKER_DEV_SERVER_HOT=false ./bin/shakapacker-dev-server
```

By default, the webpack dev server listens on `localhost:3035` in development for security purposes. However, if you want your app to be available on port 4035 over local LAN IP or a VM instance like vagrant, you can set the `port` and `host` when running `./bin/shakapacker-dev-server` binstub:

```bash
SHAKAPACKER_DEV_SERVER_PORT=4305 SHAKAPACKER_DEV_SERVER_HOST=0.0.0.0 ./bin/shakapacker-dev-server
```

**Note:** You need to allow webpack-dev-server host as an allowed origin for `connect-src` if you are running your application in a restrict CSP environment (like Rails 5.2+). This can be done in Rails 5.2+ in the CSP initializer `config/initializers/content_security_policy.rb` with a snippet like this:

```ruby
Rails.application.config.content_security_policy do |policy|
  policy.connect_src :self, :https, 'http://localhost:3035', 'ws://localhost:3035' if Rails.env.development?
end
```

**Note:** Don't forget to prefix `ruby` when running these binstubs on Windows

### Ruby API Reference

**📚 For comprehensive Ruby API documentation, see the [API Reference Guide](./docs/api-reference.md).**

This guide covers:

- **Main Shakapacker Module** - Configuration, compilation, and manifest access
- **Configuration API** - Accessing `config/shakapacker.yml` settings programmatically
- **View Helpers** - Complete reference for all Rails helpers
- **Manifest API** - Asset lookup and resolution methods
- **Dev Server API** - Development server status and management
- **Advanced Usage** - Multiple instances, testing, custom configurations

#### Quick Examples

```ruby
# Access configuration
Shakapacker.config.source_path
# => #<Pathname:/app/app/javascript>

# Get raw configuration hash
Shakapacker.config.data
# => { "source_path" => "app/javascript", ... }

# Look up compiled assets
Shakapacker.manifest.lookup("application.js")
# => "/packs/application-abc123.js"

# Check dev server status
Shakapacker.dev_server.running?
# => true
```

#### Generating Full API Documentation

For complete API documentation with all methods and parameters:

```bash
# Using YARD (recommended - better formatting)
gem install yard
yard doc
yard server  # Browse at http://localhost:8808

# Using RDoc (standard Ruby documentation)
rdoc lib/
open doc/index.html
```

The generated documentation includes all public and private methods with detailed descriptions.

#### Type Signatures with RBS

Shakapacker includes **RBS type signatures** for all public APIs, enabling static type checking and improved IDE support:

**Benefits:**

- **IDE Autocomplete**: Get accurate method signatures and parameter hints in your editor
- **Static Type Checking**: Catch type errors before runtime using [Steep](https://github.com/soutaro/steep) or [TypeProf](https://github.com/ruby/typeprof)
- **Self-Documenting Code**: Types provide machine-readable API documentation
- **Safer Refactoring**: Type checker catches breaking changes across your codebase

**RBS Signatures Location:**
Type signatures are in the `sig/` directory and included with the gem:

```
sig/
├── shakapacker.rbs                    # Main module
└── shakapacker/
    ├── configuration.rbs              # Configuration API
    ├── helper.rbs                     # View helpers
    ├── manifest.rbs                   # Asset lookup
    ├── compiler.rbs                   # Compilation
    ├── dev_server.rbs                 # Dev server
    └── ...                            # Other components
```

**Using with Steep (Type Checker):**

```yaml
# Steepfile
target :app do
signature "sig"
check "app"
library "shakapacker"
end
```

**Example Type Checking:**

```ruby
# Your code
config = Shakapacker.config
config.source_path  # Type checker knows this returns Pathname
config.webpack?     # Type checker knows this returns bool

# Type error caught at development time:
config.invalid_method  # ⚠️ Steep reports: Method `invalid_method` is not defined
```

**Learn More:**

- [RBS Documentation](https://github.com/ruby/rbs)
- [Steep Type Checker](https://github.com/soutaro/steep)
- [TypeProf](https://github.com/ruby/typeprof)

### Webpack Configuration

First, you don't _need_ to use Shakapacker's webpack configuration. However, the `shakapacker` NPM package provides convenient access to configuration code that reads the `config/shakapacker.yml` file which the view helpers also use. If you have your customized webpack configuration, at the minimum, you must ensure:

1. Your output files go to the right directory
2. Your output includes a manifest, via package [`webpack-assets-manifest`](https://github.com/webdeveric/webpack-assets-manifest) that maps output names (your 'packs') to the fingerprinted versions, including bundle-splitting dependencies. That's the main secret sauce of Shakapacker!

The webpack configuration used by Shakapacker lives in `config/webpack/webpack.config.js`; this makes it easy to customize the configuration beyond what's available in `config/shakapacker.yml` by giving you complete control of the final configuration. By default, this file exports the result of `generateWebpackConfig` which handles generating a webpack configuration based on `config/shakapacker.yml`.

#### Using a Completely Custom Webpack Configuration

If you're providing a completely custom webpack configuration without using `generateWebpackConfig()`, you should set `javascript_transpiler: 'none'` in your `config/shakapacker.yml` to skip Shakapacker's transpiler validation and dependency checks:

```yml
# config/shakapacker.yml
default: &default
  javascript_transpiler: "none" # Skip Shakapacker's transpiler setup
  # ... other config
```

This is useful when you're managing your own transpiler configuration entirely outside of Shakapacker's defaults.

**Note:** Only use `javascript_transpiler: 'none'` if you're providing a completely custom webpack configuration without using `generateWebpackConfig()`. If you're using Shakapacker's webpack generation (which is the common case), use one of the supported transpilers (`'babel'`, `'swc'`, or `'esbuild'`) instead.

The easiest way to modify this config is to pass your desired customizations to `generateWebpackConfig` which will use [webpack-merge](https://github.com/survivejs/webpack-merge) to merge them with the configuration generated from `config/shakapacker.yml`:

```js
// config/webpack/webpack.config.js
const { generateWebpackConfig } = require("shakapacker")

const options = {
  resolve: {
    extensions: [".css", ".ts", ".tsx"]
  }
}

// This results in a new object copied from the mutable global
module.exports = generateWebpackConfig(options)
```

The `shakapacker` package also exports the `merge` function from [webpack-merge](https://github.com/survivejs/webpack-merge) to make it easier to do more advanced customizations:

```js
// config/webpack/webpack.config.js
const { generateWebpackConfig, merge } = require("shakapacker")

const webpackConfig = generateWebpackConfig()

const options = {
  resolve: {
    extensions: [".css", ".ts", ".tsx"]
  }
}

module.exports = merge(options, webpackConfig)
```

This example is based on [an example project](https://github.com/shakacode/react_on_rails_tutorial_with_ssr_and_hmr_fast_refresh/blob/master/config/webpack/webpack.config.js)

Shakapacker gives you a default configuration file `config/webpack/webpack.config.js`, which, by default, you don't need to make any changes to `config/webpack/webpack.config.js` since it's a standard production-ready configuration. However, you will probably want to customize or add a new loader by modifying the webpack configuration, as shown above.

You might add separate files to keep your code more organized.

```js
// config/webpack/custom.js
module.exports = {
  resolve: {
    alias: {
      jquery: "jquery/src/jquery",
      vue: "vue/dist/vue.js",
      React: "react",
      ReactDOM: "react-dom",
      vue_resource: "vue-resource/dist/vue-resource"
    }
  }
}
```

Then `require` this file in your `config/webpack/webpack.config.js`:

```js
// config/webpack/webpack.config.js
// use the new NPM package name, `shakapacker`.
const { generateWebpackConfig } = require("shakapacker")

const customConfig = require("./custom")

module.exports = generateWebpackConfig(customConfig)
```

If you need access to configs within Shakapacker's configuration, you can import them like so:

```js
// config/webpack/webpack.config.js
const { generateWebpackConfig } = require("shakapacker")

const webpackConfig = generateWebpackConfig()

console.log(webpackConfig.output_path)
console.log(webpackConfig.source_path)

// Or to print out your whole webpack configuration
console.log(JSON.stringify(webpackConfig, undefined, 2))
```

You may want to modify the rules in the default configuration. For instance, if you are using a custom svg loader, you may want to remove `.svg` from the default file loader rules. You can search and filter the default rules like so:

```js
const fileRule = config.module.rules.find((rule) => rule.test.test(".svg"))
// removing svg from asset file rule's test RegExp
fileRule.test =
  /\.(bmp|gif|jpe?g|png|tiff|ico|avif|webp|eot|otf|ttf|woff|woff2)$/
// changing the rule type from 'asset/resource' to 'asset'. See https://webpack.js.org/guides/asset-modules/
fileRule.type = "asset"
```

### Babel configuration

If you choose to use Babel instead of the default SWC transpiler, you will need to configure it in your `package.json`:

```json
"babel": {
  "presets": [
    "./node_modules/shakapacker/package/babel/preset.js"
  ]
},
```

You can also change your Babel configuration by removing these lines in your `package.json` and adding [a Babel configuration file](https://babeljs.io/docs/en/config-files) to your project. For an example of customization based on the original, see [Customizing Babel Config](./docs/customizing_babel_config.md).

### SWC configuration

SWC is the recommended JavaScript transpiler in Shakapacker v10 (this default was introduced in v9; 20x faster than Babel). New installations use SWC by default via the installation template. You can read more at [SWC usage docs](./docs/using_swc_loader.md).

**Note on defaults**: The installation template explicitly sets `javascript_transpiler: "swc"` for new projects. However, for backward compatibility, webpack's runtime default (when no explicit config exists) remains `"babel"`. Rspack always defaults to `"swc"`.

Please note that SWC supports [React](#react) integration out of the box - no additional configuration needed.

### esbuild loader configuration

You can use esbuild as an alternative JavaScript transpiler. You can read more at [esbuild-loader usage docs](./docs/using_esbuild_loader.md).

Please note that esbuild supports [React](#react) integration out of the box - no additional configuration needed.

### Switching between transpilers

To switch between Babel, SWC, or esbuild, or to configure environment-specific transpiler settings, see the [Transpiler Migration Guide](./docs/transpiler-migration.md).

### Debugging Configuration

Shakapacker provides a powerful utility to export and analyze your webpack/rspack configuration:

```bash
# Export all configs for troubleshooting (recommended)
bin/shakapacker-config --doctor

# Or via rake task
bundle exec rake shakapacker:export_bundler_config -- --doctor
```

This exports development and production configurations for both client and server bundles to `shakapacker-config-exports/` directory in annotated YAML format. Perfect for:

- Debugging configuration issues
- Comparing webpack vs rspack configs (works with `rake shakapacker:switch_bundler`)
- Understanding differences between development and production
- Analyzing client vs server bundle configurations

For more options and usage examples, see the [Troubleshooting Guide](./docs/troubleshooting.md#exporting-webpack--rspack-configuration).

#### Comparing Configurations

Once you've exported configurations, compare them semantically with `bin/diff-bundler-config` (powered by [`pack-config-diff`](https://github.com/shakacode/pack-config-diff)):

```bash
# Compare development vs production configs
bin/diff-bundler-config \
  --left=shakapacker-config-exports/webpack-development-client.yaml \
  --right=shakapacker-config-exports/webpack-production-client.yaml

# Get a quick summary
bin/diff-bundler-config \
  --left=config1.yaml \
  --right=config2.yaml \
  --format=summary
```

This is useful for:

- Understanding environment-specific config changes
- Debugging unexpected behavior differences
- Migration validation (webpack -> rspack)
- Reviewing bundler config changes in PRs

For full usage, see the [Configuration Diff Guide](./docs/config-diff.md).

### Integrations

Shakapacker out of the box supports JS and static assets (fonts, images etc.) compilation. To enable support for CoffeeScript or TypeScript install relevant packages:

#### React

See here for detailed instructions on how to [configure Shakapacker to bundle a React app](./docs/react.md) (with optional HMR).

See also [Customizing Babel Config](./docs/customizing_babel_config.md) for an example React configuration.

#### TypeScript

**📚 TypeScript Support:** See the **[TypeScript Documentation](./docs/typescript.md)** for type-safe configuration.

```bash
npm install --save-dev typescript

# If you explicitly use `javascript_transpiler: babel`
npm install --save-dev @babel/preset-typescript
```

Shakapacker does not type-check TypeScript during builds. For webpack projects, you can optionally
add type-checking during builds with:

```bash
npm install --save-dev fork-ts-checker-webpack-plugin
```

You can also run `tsc --noEmit` separately in CI or local development if you prefer not to wire
type-checking into the bundler.

Add tsconfig.json

```json
{
  "compilerOptions": {
    "declaration": false,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "lib": ["es6", "dom"],
    "module": "es6",
    "moduleResolution": "node",
    "sourceMap": true,
    "target": "es5",
    "jsx": "react",
    "noEmit": true
  },
  "exclude": ["**/*.spec.ts", "node_modules", "vendor", "public"],
  "compileOnSave": false
}
```

Then modify the webpack config to use it as a plugin:

```js
// config/webpack/webpack.config.js
const { generateWebpackConfig } = require("shakapacker")
const ForkTSCheckerWebpackPlugin = require("fork-ts-checker-webpack-plugin")

module.exports = generateWebpackConfig({
  plugins: [new ForkTSCheckerWebpackPlugin()]
})
```

Optionally, your webpack config file itself can be written in Typescript:

```bash
npm install ts-node @types/node @types/webpack
```

```ts
// config/webpack/webpack.config.ts
import { generateWebpackConfig } from "shakapacker"
import ForkTSCheckerWebpackPlugin from "fork-ts-checker-webpack-plugin"

const config = generateWebpackConfig({
  plugins: [new ForkTSCheckerWebpackPlugin()]
})

export default config
```

#### CSS

To enable CSS support in your application, add the following packages:

```bash
npm install css-loader style-loader mini-css-extract-plugin css-minimizer-webpack-plugin
```

Optionally, add the `CSS` extension to webpack config for easy resolution.

```js
// config/webpack/webpack.config.js
const { generateWebpackConfig } = require("shakapacker")

const customConfig = {
  resolve: {
    extensions: [".css"]
  }
}

module.exports = generateWebpackConfig(customConfig)
```

To enable `PostCSS`, `Sass` or `Less` support, add `CSS` support first and
then add the relevant pre-processors:

#### Postcss

```bash
npm install postcss postcss-loader
```

Optionally add these two plugins if they are required in your `postcss.config.js`:

```bash
npm install postcss-preset-env postcss-flexbugs-fixes
```

#### Sass

```bash
npm install sass-loader
```

You will also need to install [Dart Sass](https://github.com/sass/dart-sass), [Node Sass](https://github.com/sass/node-sass) or [Sass Embedded](https://github.com/sass/embedded-host-node) to pick the implementation to use. sass-loader will automatically pick an implementation based on installed packages.

Please refer to [sass-loader documentation](https://www.npmjs.com/package/sass-loader) and individual packages repos for more information on all the options.

##### Dart Sass

```bash
npm install sass
```

##### Node Sass

```bash
npm install node-sass
```

##### Sass Embedded

```bash
npm install sass-embedded
```

#### Less

```bash
npm install less less-loader
```

#### Stylus

```bash
npm install stylus stylus-loader
```

#### CoffeeScript

```bash
npm install coffeescript coffee-loader
```

#### Other frameworks

Please follow Webpack integration guide for the relevant framework or library,

1. [Svelte](https://github.com/sveltejs/svelte-loader#install)
2. [Angular](https://v2.angular.io/docs/ts/latest/guide/webpack.html#!#configure-webpack)
3. [Vue](https://vue-loader.vuejs.org/guide/)

For example to add Vue support:

```js
// config/webpack/rules/vue.js
const { VueLoaderPlugin } = require("vue-loader")

module.exports = {
  module: {
    rules: [
      {
        test: /\.vue$/,
        loader: "vue-loader"
      }
    ]
  },
  plugins: [new VueLoaderPlugin()],
  resolve: {
    extensions: [".vue"]
  }
}
```

```js
// config/webpack/webpack.config.js
const { generateWebpackConfig, merge } = require("shakapacker")

const webpackConfig = generateWebpackConfig()

const vueConfig = require("./rules/vue")

module.exports = merge(vueConfig, webpackConfig)
```

### Custom Rails environments

Out of the box Shakapacker ships with - development, test and production environments in `config/shakapacker.yml` however, in most production apps extra environments are needed as part of the deployment workflow. Shakapacker supports this out of the box from version 3.4.0+ onwards.

You can choose to define additional environment configurations in shakapacker.yml,

```yml
staging:
  <<: *default

  # Production depends on precompilation of packs prior to booting for performance.
  compile: false

  # Cache manifest.json for performance
  cache_manifest: true

  # Compile staging packs to a separate directory
  public_output_path: packs-staging
```

Otherwise, Shakapacker will use the production environment as a fallback environment for loading configurations. Please note, `NODE_ENV` can either be set to `production`, `development` or `test`. This means you don't need to create additional environment files inside `config/shakapacker/*` and instead use shakapacker.yml to load different configurations using `RAILS_ENV`.

For example, the below command will compile assets in production mode but will use staging configurations from `config/shakapacker.yml` if available or use fallback production environment configuration:

```bash
RAILS_ENV=staging bundle exec rake assets:precompile
```

And, this will compile in development mode and load configuration for the cucumber environment if defined in `shakapacker.yml` or fallback to production configuration

```bash
RAILS_ENV=cucumber NODE_ENV=development bundle exec rake assets:precompile
```

Please note, binstubs compiles in development mode however rake tasks compiles in production mode.

```bash
# Compiles in development mode unless NODE_ENV is specified, per the binstub source
./bin/shakapacker
./bin/shakapacker-dev-server

# Compiles in production mode by default unless NODE_ENV is specified, per `lib/tasks/shakapacker/compile.rake`
bundle exec rake assets:precompile
bundle exec rake shakapacker:compile
```

### Upgrading

You can run the following commands to upgrade Shakapacker to the latest stable version. This process involves upgrading the gem and related JavaScript packages:

```bash
# check your Gemfile for version restrictions
bundle update shakapacker

# overwrite your changes to the default install files and revert any unwanted changes from the install
bundle exec rake shakapacker:install

# using npm
npm install shakapacker@latest
npm install webpack-dev-server@latest

# using yarn classic
yarn upgrade shakapacker --latest
yarn upgrade webpack-dev-server --latest

# using yarn berry
yarn up shakapacker@latest
yarn up webpack-dev-server@latest

# using pnpm
pnpm up shakapacker@latest
pnpm up webpack-dev-server@latest

# Or to install the latest release (including pre-releases)
npm install shakapacker@next
```

Also, consult the [CHANGELOG](./CHANGELOG.md) for additional upgrade links.

#### Automating Updates with Dependabot

Shakapacker is shipped as both a Ruby gem and an npm package, so they must be
upgraded together. See [Dependabot configuration for Shakapacker](./docs/dependabot.md)
for a `.github/dependabot.yml` example that updates both in a single PR.

#### Common Upgrade Scenarios

For step-by-step guides on common migrations, see the [Common Upgrades Guide](./docs/common-upgrades.md):

- [Migrating Package Managers](./docs/common-upgrades.md#migrating-package-managers) (Yarn ↔ npm, pnpm)
- [Migrating from Babel to SWC](./docs/common-upgrades.md#migrating-from-babel-to-swc) (20-70x faster builds)
- [Migrating from Webpack to Rspack](./docs/common-upgrades.md#migrating-from-webpack-to-rspack) (5-10x faster builds)

### Paths

By default, Shakapacker ships with simple conventions for where the JavaScript app files and compiled webpack bundles will go in your Rails app. All these options are configurable from `config/shakapacker.yml` file.

The configuration for what webpack is supposed to compile by default rests on the convention that every file in `app/javascript/`**(default)** or whatever path you set for `source_entry_path` in the `shakapacker.yml` configuration is turned into their own output files (or entry points, as webpack calls it). Therefore you don't want to put any file inside `app/javascript` directory that you do not want to be an entry file. As a rule of thumb, put all files you want to link in your views inside "app/javascript/" directory and keep everything else under subdirectories like `app/javascript/controllers`.

Suppose you want to change the source directory from `app/javascript` to `frontend` and output to `assets/packs`. This is how you would do it:

```yml
# config/shakapacker.yml
source_path: frontend # packs are the files in frontend/
public_output_path: assets/packs # outputs to => public/assets/packs
```

For server-side rendering (SSR) scenarios where you need to generate bundles that should not be served publicly, you can use the `private_output_path` configuration:

```yml
# config/shakapacker.yml
private_output_path: ssr-generated # outputs to => ssr-generated/
```

This is particularly useful when working with libraries like React on Rails where server bundles need to be kept separate from client bundles.

#### Migration Guide for React on Rails Users

If you're using React on Rails with separate client and server bundles, you can now leverage the `private_output_path` configuration instead of using custom webpack configurations:

1. Update your `config/shakapacker.yml`:

   ```yml
   # Before: both client and server bundles in public/
   # After: separate directories
   public_output_path: packs # Client bundles (publicly served)
   private_output_path: ssr-bundles # Server bundles (not publicly served)
   ```

2. Update your webpack configuration to use the appropriate output path based on the bundle type
3. The validation ensures `private_output_path` and `public_output_path` are different to prevent configuration errors

Similarly, you can also control and configure `webpack-dev-server` settings from `config/shakapacker.yml` file:

```yml
# config/shakapacker.yml
development:
  dev_server:
    host: localhost
    port: 3035
```

If you have `hmr` turned to true and `inline_css` is not false, then the `stylesheet_pack_tag` generates no output, as you will want to configure your styles to be inlined in your JavaScript for hot reloading. During production and testing, the `stylesheet_pack_tag` will create the appropriate HTML tags.

If you want to have HMR and separate link tags, set `hmr: true` and `inline_css: false`. This will cause styles to be extracted and reloaded with the `mini-css-extract-plugin` loader. Note that in this scenario, you do not need to include style-loader in your project dependencies.

### Additional paths

If you are adding Shakapacker to an existing app that has most of the assets inside `app/assets` or inside an engine, and you want to share that with webpack modules, you can use the `additional_paths` option available in `config/shakapacker.yml`. This lets you
add additional paths that webpack should look up when resolving modules:

```yml
additional_paths: ["app/assets", "vendor/assets"]
```

You can then import these items inside your modules like so:

```js
// Note it's relative to parent directory i.e. app/assets
import "stylesheets/main"
import "images/rails.png"
```

Assets put in these folders will also have their path stripped just like with the `source_path`.

Example:

A file in `app/assets/images/image.svg` with `additional_paths: ['app/assets']` will result in `static/images/image.svg`

**Note:** Please be careful when adding paths here otherwise it will make the compilation slow, consider adding specific paths instead of the whole parent directory if you just need to reference one or two modules

**Also note:** While importing assets living outside your `source_path` defined in shakapacker.yml (like, for instance, assets under `app/assets`) from within your packs using _relative_ paths like `import '../../assets/javascripts/file.js'` will work in development, Shakapacker won't recompile the bundle in production unless a file that lives in one of it's watched paths has changed (check out `Shakapacker::MtimeStrategy#latest_modified_timestamp` or `Shakapacker::DigestStrategy#watched_files_digest` depending on strategy configured by `compiler_strategy` option in `shakapacker.yml`). That's why you'd need to add `app/assets` to the additional_paths as stated above and use `import 'javascripts/file.js'` instead.

## Deployment

Shakapacker hooks up a new `shakapacker:compile` task to `assets:precompile`, which gets run whenever you run `assets:precompile`. If you are not using Sprockets, `shakapacker:compile` is automatically aliased to `assets:precompile`. Similar to sprockets both rake tasks will compile packs in production mode but will use `RAILS_ENV` to load configuration from `config/shakapacker.yml` (if available).

This behavior is optional & can be disabled by either setting a `SHAKAPACKER_PRECOMPILE` environment variable to `false`, `no`, `n`, or `f`, or by setting a `shakapacker_precompile` key in your `shakapacker.yml` to `false`. ([source code](./lib/shakapacker/configuration.rb#L34))

When compiling assets for production on a remote server, such as a continuous integration environment, it's recommended to ensure the exact versions specified in your lockfile are installed:

```
# using npm
npm ci

# using yarn classic
yarn install --frozen-lockfile

# using yarn berry
yarn install --immutable

# using pnpm
pnpm install --frozen-lockfile

# using bun
bun install --frozen-lockfile
```

### CDN

Shakapacker supports serving JavaScript bundles and assets from a CDN. The key configuration is setting the `SHAKAPACKER_ASSET_HOST` environment variable (NOT the Rails `ASSET_HOST` variable).

For detailed CDN setup instructions, including CloudFlare configuration, troubleshooting, and advanced setups, see the [CDN Setup Guide](./docs/cdn_setup.md).

**Quick example:**

```bash
export SHAKAPACKER_ASSET_HOST=https://cdn.example.com
RAILS_ENV=production bundle exec rake assets:precompile
```

For more deployment documentation, see [Deployment](./docs/deployment.md).

## Example Apps

- [React on Rails Tutorial With SSR, HMR fast refresh, and TypeScript](https://github.com/shakacode/react_on_rails_tutorial_with_ssr_and_hmr_fast_refresh)

## Troubleshooting

See the doc page for [Troubleshooting](./docs/troubleshooting.md).

## Contributing

We encourage you to contribute to Shakapacker! See [CONTRIBUTING](CONTRIBUTING.md) for guidelines about how to proceed. We have a [Slack discussion channel](https://reactrails.slack.com/join/shared_invite/enQtNjY3NTczMjczNzYxLTlmYjdiZmY3MTVlMzU2YWE0OWM0MzNiZDI0MzdkZGFiZTFkYTFkOGVjODBmOWEyYWQ3MzA2NGE1YWJjNmVlMGE).

## License

Shakapacker is released under the [MIT License](https://opensource.org/licenses/MIT).

## Supporters

The following companies support our Open Source projects, and ShakaCode uses their products!

<br />
<br />

<a href="https://jb.gg/OpenSource" style="margin-right: 20px;">
  <img src="https://resources.jetbrains.com/storage/products/company/brand/logos/jetbrains.png" alt="JetBrains" height="120px">
</a>
<a href="https://scoutapp.com">
  <picture>
    <source media="(prefers-color-scheme: dark)" srcset="https://user-images.githubusercontent.com/4244251/184881147-0d077438-3978-40da-ace9-4f650d2efe2e.png">
    <source media="(prefers-color-scheme: light)" srcset="https://user-images.githubusercontent.com/4244251/184881152-9f2d8fba-88ac-4ba6-873b-22387f8711c5.png">
    <img alt="ScoutAPM" src="https://user-images.githubusercontent.com/4244251/184881152-9f2d8fba-88ac-4ba6-873b-22387f8711c5.png" height="120px">
  </picture>
</a>
<a href="https://shakacode.controlplane.com">
  <picture>
    <img alt="Control Plane" src="https://github.com/shakacode/.github/assets/20628911/90babd87-62c4-4de3-baa4-3d78ef4bec25" height="120px">
  </picture>
</a>
<br />
<a href="https://www.browserstack.com">
  <picture>
    <source media="(prefers-color-scheme: dark)" srcset="https://user-images.githubusercontent.com/4244251/184881122-407dcc29-df78-4b20-a9ad-f597b56f6cdb.png">
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    <img alt="BrowserStack" src="https://user-images.githubusercontent.com/4244251/184881129-e1edf4b7-3ae1-4ea8-9e6d-3595cf01609e.png" height="55px">
  </picture>
</a>
<a href="https://www.honeybadger.io">
  <img src="https://user-images.githubusercontent.com/4244251/184881133-79ee9c3c-8165-4852-958e-31687b9536f4.png" alt="Honeybadger" height="55px">
</a>
<a href="https://coderabbit.ai">
  <picture>
    <source media="(prefers-color-scheme: dark)" srcset="https://victorious-bubble-f69a016683.media.strapiapp.com/White_Typemark_7229870ac5.svg">
    <source media="(prefers-color-scheme: light)" srcset="https://victorious-bubble-f69a016683.media.strapiapp.com/Orange_Typemark_7958cfa790.svg">
    <img alt="CodeRabbit" src="https://victorious-bubble-f69a016683.media.strapiapp.com/Orange_Typemark_7958cfa790.svg" height="55px">
  </picture>
</a>