100% JavaScript Project

Jordan Hairband chooses to not include TypeScript definitions in Tape:

No. Typings should never be packaged with individual repos, especially because maintainers who don't use typescript have no friendly way to keep the typings in sync.

DT or similar is the proper place for types, until JavaScript has them natively.

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The tape codebase will not be written in anything but JavaScript.

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I would encourage you, however, to submit accurate typings for all the tape versions to DT, to benefit all TypeScript users - and if there’s anything short of using TS that i can do to make it easier for TS users to use tape, I’d be happy to.

Mentioning TypeScript in README is also refused:

I don’t think that’s necessary. A typescript user should already know how to use ts-node with everything if needed, and the advice isn’t different with tape than with anything else. It’s not incumbent on “every individual non-typescript package” to make typescript easy to use; that’s typescript’s task.

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...an alternative without ts-node is to transpile first and test the output.

This is just the sort of thing that you open yourself to by making the choice to use “not JavaScript”, and it’s not practical for millions of individual JS packages to try to document all the caveats you need to know when making that choice.

Besides, strictly speaking, if a library includes .d.ts, then it needs to add typescript as its dependency not dev dependency. Otherwise, if the type definitions include features not available on old versions of TypeScript, or not compatible with breaking changes from future versions of TypeScript, it will not work for the library users, at least causing problems on their IDEs or editors.

If types are published under @types/foo, users of the library need to install an additional package. Also, this separation requires extra configuration for the package maintainers.

To be honest, TypeScript may be considered as a special case. TypeScript is not added to the dependencies list, assuming the type definitions of the library will work with all recent TypeScript versions. And the users of the library can install the right TypeScript version manually specified in the dev dependencies, as a last resort, if they encountered problems, which should be a rare condition. Although this dependency specification is not rigid, it should work well in practical.