@rsbuild/plugin-source-build

An Rsbuild plugin to provide support for monorepo source code referencing.

@rsbuild/plugin-source-build allows referencing source code from other subdirectories of monorepo and performs the build and hot updates.

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Usage

Install:

npm add @rsbuild/plugin-source-build -D

Add plugin to your rsbuild.config.ts:

// rsbuild.config.ts
import { pluginSourceBuild } from '@rsbuild/plugin-source-build';

export default {
  plugins: [pluginSourceBuild()],
};

Use Cases

In a monorepo, there are two main ways for projects to reference each other: artifact referencing and source code referencing. Let's use a simple monorepo as an example to illustrate the use case of source code referencing.

For example, the monorepo contains an app application and a lib:

monorepo
├── app
└── lib
    └── src
        └── index.ts

The app is built using Rsbuild and relies on some methods from the lib:

{
  "name": "app",
  "dependencies": {
    "lib": "workspace:*"
  }
}

Artifact Referencing

When using artifact referencing, the current project references the artifacts built from other sub-projects.

In the example above, the lib is written in TypeScript. Typically, we need to build the lib's code in advance to generate JavaScript artifacts so that the app can reference it correctly. When the lib's code is updated, we need to rebuild it (or use tsc --watch) to ensure that the app can use the latest code.

The advantages of this approach are:

• The build processes of each sub-project are completely independent and can have different build configurations.
• Build caching can be applied to individual sub-projects.

The disadvantages are:

• The HMR chain becomes longer during local development.
• The process becomes cumbersome when a project contains multiple lib packages.

Source Code Referencing

When using source code referencing, the current project references the source code of other sub-projects for building.

In the example mentioned earlier, when you register the @rsbuild/plugin-source-build and add the relevant configuration in the lib directory, Rsbuild will automatically reference the src/index.ts source code of the lib. This means that you don't need to build the lib's code in advance, and when the source code of the lib is updated, it can trigger automatic hot updates for the app.

The advantages of this approach are:

• The sub-project does not rely on a build tool and does not require build configurations. The code of the sub-project will be compiled by the build tool of the current project.
• There is no need to execute the build process for the sub-projects in advance.
• HMR is more efficient during local development.

The disadvantages are:

• The current project needs to support syntax features used by sub-projects and follow the same syntax specifications, such as using a consistent version of decorator syntax. If the current project and sub-projects require different build configurations, building from source code may not be suitable.
• The current project requires compiling more code, which may result in longer build times.

Configuring Sub-projects

When the @rsbuild/plugin-source-build is registered, the Rsbuild will prioritize reading the file specified in the source field of the sub-project during the build process. Therefore, you need to configure the source field in the package.json file of the sub-project and point it to the source code file.

For example, in the following example, when the lib package is referenced, the ./src/index.ts file will be read for building:

{
  "name": "lib",
  "main": "./dist/index.js",
  "source": "./src/index.ts"
}

If the sub-project uses the exports field, you also need to add the source field to exports.

Note that the declaration order of keys in exports affects resolution, so it is recommended to place the source field first in each export condition object to ensure the resolver prioritizes the module pointed to by source.

{
  "name": "lib",
  "exports": {
    ".": {
      "source": "./src/index.ts",
      "default": "./dist/index.js"
    },
    "./features": {
      "source": "./src/features/index.ts",
      "default": "./dist/features/index.js"
    }
  }
}

Customizing Source Field

Although the plugin uses the source field by default to specify the source file, we recommend configuring a custom field through the sourceField option (for example, @custom/source, where custom can be replaced with any scope name).

pluginSourceBuild({
  sourceField: '@custom/source',
});

This is because some packages (such as Mobx) also define a source field in their package.json. If not distinguished, Rsbuild may mistakenly resolve the source files of those dependencies, leading to unexpected build results or type issues. By using a custom field, you can avoid such conflicts and ensure that Rsbuild behaves predictably when resolving dependencies.

Configure Project Reference

In a TypeScript project, you need to use the capability provided by TypeScript called Project Reference. It helps you develop source code more effectively.

Introduction

Project reference provides the following capabilities:

• It allows TypeScript to correctly recognize the types of other sub-projects without the need to build them.
• When you navigate the code in VS Code, it automatically takes you to the corresponding source code file of the module.
• Rsbuild reads the project reference configuration and automatically recognizes the tsconfig.compilerOptions.path configuration of the sub-project, so that the use of aliases in the sub-project works correctly.

Example

In the example mentioned earlier, since the app project references the lib sub-project, we need to configure the references options in the app project's tsconfig.json to point to the relative directory of the lib:

{
  "references": [
    {
      "path": "../lib"
    }
  ]
}

At the same time, we need to set composite to true in the lib project's tsconfig.json:

{
  "compilerOptions": {
    "composite": true
  }
}

After adding these two options, the project reference is already configured. You can restart VS Code to see the effects of the configuration.

Note that the above example is a simplified one. In real monorepo projects, there may be more complex dependency relationships. You need to add a complete references configuration for the functionality to work correctly.

If you want to learn more about project reference, please refer to the official documentation on TypeScript - Project References.

Options

sourceField

• Type: string
• Default: 'source'

Used to configure the resolve field of the source code files.

For example, when configured as @custom/source:

pluginSourceBuild({
  sourceField: '@custom/source',
});

In package.json, the source code file path can be specified using @custom/source:

{
  "name": "lib",
  "main": "./dist/index.js",
  "@custom/source": "./src/index.ts",
  "exports": {
    ".": {
      "@custom/source": "./src/index.ts",
      "default": "./dist/index.js"
    }
  }
}

If you use a custom field name configured via sourceField in exports (for example, @custom/source), place that field first in each export condition object, since the key order in exports affects resolution priority.

resolvePriority

• Type: 'source' | 'output'
• Default: 'source'

Used to control the priority of reading the source code or the output code.

By default, @rsbuild/plugin-source-build will reading the source code first, for example, in the following example, it will read the source field.

{
  "name": "lib",
  "main": "./dist/index.js",
  "source": "./src/index.ts"
}

When resolvePriority is set to 'output', @rsbuild/plugin-source-build will read the output code first, i.e., the code from the main or module field.

pluginSourceBuild({
  resolvePriority: 'output',
});

• The exports field in package.json is not affected by resolvePriority.
• The keys order in exports determines the resolving order, earlier declared keys having higher priority.

Caveat

When using @rsbuild/plugin-source-build, there are a few things to keep in mind:

1. Ensure that the current project can compile the syntax or features used in the sub-project. For example, if the sub-project uses Stylus to write CSS, the current app needs to support Stylus compilation.
2. Ensure that the current project has the same code syntax and features as the sub-project, such as consistent syntax versions for decorators.
3. Source code building may have some limitations. When encountering issues, you can remove the source field from the sub-project's package.json and debug using the built artifacts of the sub-project.
4. When composite: true is enabled, TypeScript will generate *.tsbuildinfo temporary files. You need to add these temporary files to the .gitignore file.

*.tsbuildinfo

License

MIT.