Specifying supported TypeScript versions #32166

Search Terms

version
minimal version
minimum version
typesVersions

Suggestion

Specifying the minimal TypeScript version supported by a project.

With typesVersions, fallbacks can be specified for earlier versions. But we cannot specify which earlier versions are not supported.

Use Cases

Better error reporting for users using older TypeScript versions.

Examples

execa types only support TypeScript >= 3.4 because of how the readonly keyword is used.

There should be a way for us to specify this. One way would be to extend the typesVersions field to add this feature.

Our users would then get a clear error message similar to the one produced by the engines.node field for Node.js versions. Instead at the moment, we get GitHub issues from users using older TypeScript versions.

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.