[@rollup/plugin-typescript]: sourceMap file generated by rollup references compiled sources rather than original sources

[bcoe]

• Rollup Plugin Name: @rollup/plugin-typescript
• Rollup Plugin Version: 12.1.2
• Rollup Version: 4.30.0
• Operating System (or Browser): OSX
• Node Version: v22.5.1
• Link to reproduction: https://stackblitz.com/edit/rollup-repro-jpncfvkh?file=build%2Findex.cjs.map

Expected Behavior

The content of build/index.cjs.map should reference the original .ts files that rollup has built build/index.cjs from, i.e.,

• sourcesContent contains the original .ts source files.
• the ranges in mappings reference character positions in the original .ts files.

Actual Behavior

• sourcesContent contains the transpiled JavaScript code, with TypeScript annotations removed.
• mappings appears to also reference the transpiled positions in code, rather than the original positions.

Additional Information

[cristian-eriomenco]

I have tried to setup a gazillion times sourcemapping with rollup + ts but never had luck. There's always a bug somewhere. It would help a lot if the author provided a full working example that is maintained which is a realistic use case with tree shaking working. terser, commonjs and preserveModules: true, and paths in tsconfig defined.

Our team can't debug code efficiently, I've reached a point where I feel like searching for an alternative due to lack of simple working demo. Lots of repeated github issues on this, SO questions from 2020 yet no solution or help.

A simple integration example aka:

const core = {
  input: ['./src/index.ts'],
  output: ['esm', 'cjs'].map((name) => ({
    dir: `dist/${name}`,
    format: name,
    preserveModules: true,
    preserveModulesRoot: 'src',
    sourcemap: true,
    exports: 'named',
  })),
  plugins: [
    peerDepsExternal(),
    resolve(),
    commonjs({ include: ['node_modules/**'] }),
    json(),
    typescript({
      tsconfig: './tsconfig.rollup.json',
      sourceMap: true,
      inlineSources: true,
    }),
    terser(),
  ],
};

That guarantees:

1. Typescript intellisense works.
2. Source map works
3. Tree shaking works
4. Path aliases work
5. preserveModules: true