[rezonant]

Sure-- the first issue is that NPM is a JavaScript registry, and it's bad form to restrict usage of your library to Typescript projects, or require non TS users to go through hoops to use your code. Additionally, if your own project executes as JavaScript (the vast majority of cases other than sort of Deno), your project will need to do special work to have JS files produced for the TS only library-- by default this won't happen so imports to the library will fail at runtime. When you do add node_modules/some-package to your TS project, this will change the structure of the files emitted into your output directory (assuming you use one, which is highly recommended), creating weird pathing like dist/src/main.js. Also the module would end up in dist/node_modules/some-package, which would be fine as long as the package isn't using non-code files within its module, which it likely is. And of course, you'd be missing all export information within that folder, which is likely to break imports, so you'll need to copy the package.json....

This is all a massive breach of encapsulation.

Is it possible to consume a TS only library distributed via NPM in a Node.js Typescript project? Yes, certainly. Is it ergonomic for consumers? No, certainly not.

Overall, it will be a bad experience for a lot of environments where JS files are expected to be present but aren't. Deno is probably the only environment that can consume NPM packages where it could conceivably work.