jarle/Bun Overrides and resolutions

Overrides and resolutions

Control metadependency versions with npm overrides and Yarn resolutions

Bun supports npm's "overrides" and Yarn's "resolutions" in package.json. These are mechanisms for specifying a version range for metadependencies—the dependencies of your dependencies.

{
  "name": "my-app",
  "dependencies": {
    "foo": "^2.0.0"
  },
  "overrides": { // [!code ++]
    "bar": "~4.4.0" // [!code ++]
  } // [!code ++]
}

By default, Bun will install the latest version of all dependencies and metadependencies, according to the ranges specified in each package's package.json. Let's say you have a project with one dependency, foo, which in turn has a dependency on bar. This means bar is a metadependency of our project.

{
  "name": "my-app",
  "dependencies": {
    "foo": "^2.0.0"
  }
}

When you run bun install, Bun will install the latest versions of each package.

node_modules
├── [email protected]
└── [email protected]

But what if a security vulnerability was introduced in [email protected]? We may want a way to pin bar to an older version that doesn't have the vulnerability. This is where "overrides"/"resolutions" come in.

---

"overrides"

Add bar to the "overrides" field in package.json. Bun will defer to the specified version range when determining which version of bar to install, whether it's a dependency or a metadependency.

<Note> Bun currently only supports top-level `"overrides"`. [Nested overrides](https://docs.npmjs.com/cli/v9/configuring-npm/package-json#overrides) are not supported. </Note>

{
  "name": "my-app",
  "dependencies": {
    "foo": "^2.0.0"
  },
  "overrides": { // [!code ++]
    "bar": "~4.4.0" // [!code ++]
  } // [!code ++]
}

"resolutions"

The syntax is similar for "resolutions", which is Yarn's alternative to "overrides". Bun supports this feature to make migration from Yarn easier.

As with "overrides", nested resolutions are not currently supported.

{
  "name": "my-app",
  "dependencies": {
    "foo": "^2.0.0"
  },
  "resolutions": { // [!code ++]
    "bar": "~4.4.0" // [!code ++]
  } // [!code ++]
}