⚡ serverless-rspack

Serverless Framework plugin for zero-config JavaScript and TypeScript code bundling using the high performance Rust-based JavaScript bundler rspack

Look for the plugin under the /libs directory.

Example serverless projects are under the /examples directory.

For Developers - DEVELOPER.MD

Features

• From zero to hero: configuration possibilities range from zero-config to fully customizable
• Build and runtime performance at its core
• Supports sls package, sls deploy, sls deploy function
• Integrates with Serverless Invoke Local & serverless-offline

Table of Contents

• Install
  • Serverless V4
• Plugin Options
  • Examples
  • Options
    • Read-only default Rspack Options
• Supported Runtimes
• Advanced Configuration
  • Config File
    • Config File Merge Strategies
  • External Dependencies
  • Scripts
    • Function Scripts
    • Global Scripts
  • Doctor
• Integrations
  • Serverless Offline
• Known Issues

Install

# install `serverless-rspack`
yarn add --dev @kitchenshelf/serverless-rspack
# or
npm install -D @kitchenshelf/serverless-rspack
# or
pnpm install -D @kitchenshelf/serverless-rspack

Add the following plugin to your serverless.yml:

plugins:
  - @kitchenshelf/serverless-rspack

Serverless v4 requirement

If you are using Serverless v4 you must disable the default builtin ESBuild support in your serverless.yml

build:
  esbuild: false

Plugin Options

By default, no plugin options is required, but you can override the reasonable defaults via the custom.rspack section in the serverless.yml file.

custom:
  rspack:
    mode: 'production'
    esm: true

Examples

See example folder for example plugin option configuration.

Options

Option	Description	Default
zipConcurrency	The number of concurrent zip operations to run at once. eg. 8. NOTE: This can be memory intensive and could produce slower builds.	Infinity
keepOutputDirectory	Keeps the .rspack output folder. Useful for debugging.	false
stats	Generate packaging information that can be used to analyze module dependencies and optimize compilation speed.	false
config	rspack config options.	undefined
config.path	Relative rspack config path.	undefined
config.strategy	Strategy to use when a rspack config is provided.	override
esm	Output format will be ESM (experimental).	false
mode	Used to set the build mode of Rspack to enable the default optimization strategy (https://www.rspack.dev/config/mode).	production
tsConfig	Relative path to your tsconfig.	undefined
sourcemap	Configure rspack sourcemaps.	false
externals	Provides a way of excluding dependencies from the output bundles.	undefined
scripts	Array of scripts to execute after your code has been bundled by rspack.	undefined
doctor	Enable the Rsdoctor plugin.	undefined

Read-only default Rspack Options

The following rspack options are automatically set and cannot be overwritten.

Option	Notes
entry	Handler entries are determined by the plugin
output.path	The plugin needs to have full control over where bundles are output to, so it can correctly create zip artifacts

Function Options

Option	Description	Default
rspack	Set this property on a function definition to force the handler to be processed by the plugin	undefined

Supported Runtimes

This plugin will automatically process any function that has a runtime that starts with node i.e nodejs20.x

Non-Node functions

If you wish to use this plugin alongside non Node functions like Python or functions with images, this plugin will automatically ignore any function which does not match the supported runtimes.

If you wish to force a function to be process set rspack: true on a function definition. This is handy when using custom provided node runtimes i.e runtime: 'provided.al2023'

⚠️ Note: this will only work if your custom runtime and function are written in JavaScript/Typescript. Make sure you know what you are doing when this option is set to true

Advanced Configuration

Config file

Rspack configuration can be defined by a config file.

custom:
  esbuild:
    config:
      path: './rspack.config.js'

// rspack.config.js
module.exports = (serverless) => {
  external: ['lodash'],
  // etc
};

You can also return an async function.

module.exports = async (serverless) => {
  const getExternals = new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(['lodash']);
    }, 250);
  });

  const externals = await getExternals;
  
  return {
    external: externals,
    // etc
  };
};

Config file merge strategies

You can change how the plugin uses a provided config via the strategy option:

custom:
  esbuild:
    config:
      path: './rspack.config.js'
      strategy: combine

1. override: Default - Enables power users to provided their own complete Rspack configuration: rspack.config.js -> PluginReadOnlyDefaults
2. combine: Enables providing partial configuration. Merges all configuration together: PluginDefaults -> PluginOptions -> rspack.config.js -> PluginReadOnlyDefaults.

⚠️ **Note: Pay attention to the order in which configuration is combined. Each time the right take precedence. **

External Dependencies

By providing a regex you can mark packages as external and they will be excluded from the output bundles.

custom:
  rspack:
    externals:
      - "^@aws-sdk\/.*$"
      - "^@smithy\/.*$"
      - '^isin-validator$'

Scripts

Run custom shell commands after your code has been bundled by rspack. This is useful for modifying the output of the build before it is packaged.

There are two types of scripts:

1. Function: Executed once per defining function after the bundle step.
2. Global: Executed once before the package step.

Order: bundle -> function scripts -> global scripts -> package

⚠️ Note: Scripts run sequentially and will fail the build if any errors occur in any of the scripts.

The following environment variables are available to all your scripts:

• process.env: All system environment variables.
• KS_SERVICE_DIR: The absolute path to the service directory (e.g. /Users/user/code/my-service).
• KS_BUILD_OUTPUT_FOLDER: The name of the build output folder (e.g. .rspack).
• KS_PACKAGE_OUTPUT_FOLDER: The name of the package output folder (e.g. .serverless).

Function Scripts

Scripts are executed from the function directory in the output folder i.e .rspack/<function-name>.

Usage

functions:
  app3:
    handler: src/App3.handler
    runtime: nodejs20.x
    rspack:
      enable: true
      scripts:
        - 'echo "First function script"'
        - 'npx npm init -y && npm install --force --os=linux --cpu=x64 --include=optional sharp @img/sharp-linux-x64'
        - 'cp $KS_SERVICE_DIR/src/my-image.jpeg ./'
        - 'echo "Last function script"'

The following extra environment variables are available to your function scripts:

• KS_FUNCTION_NAME: The name of the function being processed.

Global Scripts

Scripts are executed from the root of the service directory.

Usage

custom:
  rspack:
    externals: ['^@aws-sdk/.*$'],
    scripts:
      - 'echo "First global script"'
      - 'echo "Last global script"'

Doctor

Rsdoctor is a one-stop tool for diagnosing and analyzing the build process and build artifacts.

The serverless-rspack plugin will automatically enable the Rsdoctor plugin when the doctor option is provided.

custom:
  rspack:
    doctor: true

You can also provide an outputDirectory to specify where the report should be saved. By default, the report will be saved in the .rspack folder.

custom:
  rspack:
    doctor:
      enable: true
      outputDirectory: ./doctor-report

⚠️ Note: Rsdoctor is configured to run in brief mode. If you want to use another mode, you can register RsdoctorRspackPlugin manually using the rspack config option.

Integrations

Serverless Offline

The plugin has first class support for serverless-offline.

Add the plugins to your serverless.yml file and make sure that serverless-rspack precedes serverless-offline as the order is important:

plugins: ...
  - serverless-rspack
  ...
  - serverless-offline
  ...

Run serverless offline start to start the Lambda/API simulation.

⚠️ Note: The plugin will automatically set sourcemap to source-map when running in offline mode and change the devtoolModuleFilenameTemplate to [absolute-resource-path].

⚠️ Note: If you are using a custom rspack config, then the serverless plugin passed to your config function will have offlineMode set to true.

Known Issues

• Invoke Local does not work with ESM enabled when using serverless V3: ISSUE-11308

---

---

---

Inspired by serverless-plugin-typescript, serverless-webpack and serverless-esbuild