import assertion get removed from output

[ivanhofer]

When bundling an 'esm' file that include import assertions, they are missing in the generated output.

Repo with reproduction: https://github.com/ivanhofer/tsup-import-assertion-bug

In /esbuild/index.js the import assertion are here, but in /tsup/index.mjs they are missing.

I would expect tsup to also include the import assertions in the generated output.

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[await-ovo]

Hi, since tsup's default target is node14, so import assertions will finally be transformed. you can specify target to esnext according to esbuild's syntax features in tsup.config.ts:

import { defineConfig } from 'tsup'

export default defineConfig([
  {
    name: 'main',
    entry: ['./src/index.ts'],
    outDir: './tsup',
    format: ['esm'],
    target: 'esnext'
  }
])

Or config target in tsconfig.json(supported in v6.4.0)