tslib doesn't have file extension

[tu4mo]

• Rollup Plugin Name: @rollup/plugin-typescript
• Rollup Plugin Version: 3.0.0
• Rollup Version: 1.31.1
• Operating System (or Browser): Mac
• Node Version: 12.16.1

How Do We Reproduce?

Run Rollup with preserveModules.

Expected Behavior

_virtual/_tslib has an .js extension.

Actual Behavior

_virtual/_tslib does not have file extension.

[shellscape]

Thanks for opening an issue. Citing the issue template:

Issues without minimal reproductions will be closed! Please provide a link to one by:

1. Using the REPL at https://rollupjs.org/repl/, or
2. Using the REPL.it reproduction template at https://repl.it/@rollup/rollup-repro
   (allows full use of all rollup options and plugins), or
3. Provide a minimal repository link (Read https://git.io/fNzHA for instructions).
   These may take more time to triage than the other options.

Please add a reproduction and we'll be happy to reopen and triage further.

[tu4mo]

@shellscape Here you go: https://repl.it/repls/OrdinaryDefiniteFormula

[shellscape]

@NotWoods I reopened this as OP provided a repro

[NotWoods]

Fixed in version 4.0.0 of the typescript plugin