[Lit] TanStackFormController types don't work when used in a library repo (tsconfig moduleResolution set to "nodenext" or "node16")

[lirobinxc]

Describe the bug

Issue

If you try to import TanStackFormController in a Lit component project where tsconfig moduleResolution is set to "nodenext" or "node16", the types don't work.

Cause

This is because in the index.ts of lit-form, TanStackFormController is exported using a relative file path:

export { TanStackFormController } from './tanstack-form-controller'

Relative (extension-less) file paths often have downstream issues in consuming repos. For widest compatibility, libraries should use explicit file path export/imports. TS recommends setting moduleResolution to "nodenext" or "node16" for libraries, which will also enable compiler checking to ensure .js file extensions are present.

Suggested solution

Add the .js file extension to library exports. In this case:

export { TanStackFormController } from './tanstack-form-controller.js'

Your minimal, reproducible example

https://codesandbox.io/p/devbox/lucid-christian-mn2vg6?file=%2Fsrc%2Findex.ts%3A4%2C49

Steps to reproduce

See this forked Lit form example: https://codesandbox.io/p/devbox/lucid-christian-mn2vg6?file=%2Fsrc%2Findex.ts%3A4%2C49

tsconfig.json moduleResolution and module have been set to "NodeNext". Notice that in index.ts, #form is now typed as any.

Expected behavior

  #form = new TanStackFormController(this, {
    defaultValues: {
      employees: [] as Employee[],
    },
  })

#form should be properly typed.

How often does this bug happen?

Every time

Screenshots or Videos

No response

Platform

• OS: MacOS

TanStack Form adapter

lit-form

TanStack Form version

v1.3.2

TypeScript version

v5.6.2

Additional context

No response