Use Biome in big projects

Biome can provide some tools that can help you to use it properly in big projects, such as monorepo or workspaces that contain multiple projects.

Use multiple configuration files

When you use Biome’s features - either with the CLI or LSP - the tool looks for the nearest configuration file using the current working directory.

If Biome doesn’t find the configuration file there, it starts walking upwards the directories of the file system, until it finds one.

You can leverage this feature to apply different settings based on the project/folder.

Let’s suppose we have a project that contains a backend app and new frontend app.

app
├── backend
│   ├── biome.json
│   └── package.json
└── frontend
    ├── biome.json
    ├── legacy-app
    │   └── package.json
    └── new-app
        └── package.json

This means that when you run a script from the file app/backend/package.json, Biome will use the configuration file app/backend/biome.json.

When you run a script from app/frontend/legacy-app/package.json or app/frontend/new-app/package.json, Biome will use the configuration file app/frontend/biome.json.

It’s possible to use the extends configuration option to breakdown options across files.

Let’s assume that we have these requirements:

legacy-app have to format using spaces;
backend and new-app have to format using tabs;
all apps have to format using line width 120;
backend app needs some extra linting;

We start by creating a new configuration file at app/biome.json, and put there the shared options:

{
  "formatter": {
    "enabled": true,
    "lineWidth": 120
  }
}

Now let’s move app/frontend/biome.json to app/frontend/legacy-app/, because that’s where we need to use a different formatting.

{
  "formatter": {
    "indentStyle": "space"
  }
}

Then, we tell Biome to inherit all the options from the main app/biome.json file, using the extends property:

{
   "extends": ["../../biome.json"],
   "formatter": {
     "indentStyle": "space"
   }
}

Let’s jump to app/backend/biome.json, where we need to enable the linting:

{
  "extends": ["../biome.json"],
    "linter": {
      "enabled": "true",
      "rules": {
        "recommended": true
      }
   }
}

Use Biome in big projects

Use multiple configuration files

Share the configuration