Add option to include default typeRoots when overriding typeRoots

Search Terms

default typeRoots

Suggestion

By default, when typeRoots is unspecified, TypeScript looks for node_modules/@types in the project's directory and all ancestor directories, similar to Node's module resolution algorithm. This is covered in the tsconfig.json docs and is implemented here.

When specifying typeRoots in tsconfig.json, this overrides the default typeRoots entirely. You can include "node_modules/@types" in your typeRoots array, but that does not include ancestor directories.

This is a feature request to provide a way, such as a new option, to include the default type roots in addition to the overridden values.

Use Cases

The primary use case is within a repository using Yarn workspaces. Yarn hoists npm packages to the workspace root. This means you can end up with a directory hierarchy like this:

.
├── node_modules
│   └── @types
│       └── dependency
└── packages
    └── example
        ├── example.ts
        ├── package.json
        └── tsconfig.json

If tsconfig.json wants to include node_modules/@types in the workspace root (in addition to other type declaration directories specified in typeRoots), it needs to look like this:

{
  "compilerOptions": {
    "typeRoots": ["../../node_modules/@types", ...]
  }
}

Examples

This feature request is a quality-of-life improvement to instead allow for:

{
  "compilerOptions": {
    "typeRoots": [...],
    "includeDefaultTypeRoots": true
  }
}

The default value of this option would be false and would not be a breaking change.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Bắt đầu với src/compiler/moduleNameResolver.ts quanh các dòng được liên kết và xem lại tài liệu tsconfig.json mô tả việc phân giải typeRoots mặc định. Xác định cách một thiết lập opt-in kết hợp các root được liệt kê rõ ràng với các thư mục node_modules/@types của các thư mục tổ tiên, sau đó bổ sung coverage cho hệ thống phân cấp workspace và xác nhận rằng hành vi mặc định vẫn không thay đổi.