tsup.config.ts

// tsup.config.ts
//
// Note: this deliberately does not `import { defineConfig } from 'tsup'`.
// Doing so makes tsup bundle itself into the config module, which then fails
// with "Dynamic require of \"fs\" is not supported". A plain object works and
// is type-checked structurally by tsup all the same.

export default {
  // Named entries so the output filenames are stable and match package.json's
  // "exports" map:
  //   .       -> dist/npm-main.js  / dist/npm-main.mjs  / dist/npm-main.d.ts
  //   ./wasm  -> dist/wasm.js      / dist/wasm.mjs      / dist/wasm.d.ts
  entry: {
    'npm-main': 'src/npm-main.ts',
    wasm: 'src/wasm.ts',
  },
  outDir: 'dist',

  format: ['cjs', 'esm'] as ('cjs' | 'esm')[],
  target: 'es2020',

  dts: true,
  clean: true,

  // Single-file outputs per entry.
  splitting: false,
  sourcemap: true,

  // .cjs -> .js, .esm -> .mjs
  outExtension({ format }: { format: string }) {
    if (format === 'esm') return { js: '.mjs' };
    return { js: '.js' };
  },
};