Support declaring @types as the supported route for typings dependencies in the package.json

Search Terms

package json types field types types module

Suggestion

Allow libraries written in JavaScript to be able to declare that they have types in DT (or other modules), and that they support a certain version of it.

For example:

Express does not support TypeScript but trusts that the DefinitelyTyped express maintainers know what they are doing generally. They want to declare that DT is the way for TypeScript users to get types out of the box. Today that's not really possible.

Examples

Two potential routes:

1. Override the "types" parameter to support: "types": "@types/express:^3.0" in a package.json

2. Recommend a new field in the package.json: "typesModule": "@types/express:^3.0" - then when TypeScript normally offers a 'no types found', then it can offer the command to install with the correct semver range.

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.

/cc @wesleytodd @isaacs @ljharb

Start by reviewing how TypeScript reads package.json metadata and the existing “no types found” path; the issue names no source files or tests. The design must first choose and specify how a package declares an external typings module and its supported semver range, then verify that TypeScript can use that declaration to guide installation.