Typescript in .ts files throws error

[zookini]

When I try to build with a .ts file containing typescript I get an error e.g.:

src/main.ts → public/build/bundle.js...
[!] Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
src\main.ts (10:5)
 8: });
 9:
10: let x: string = "oops";
         ^
11:
12: export default app;
Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
    at error (C:\Users\kl730355\Code\threat-intel\node_modules\rollup\dist\shared\rollup.js:5309:30)
    at Module.error (C:\Users\kl730355\Code\threat-intel\node_modules\rollup\dist\shared\rollup.js:9765:16)
    at Module.tryParse (C:\Users\kl730355\Code\threat-intel\node_modules\rollup\dist\shared\rollup.js:10169:25)
    at Module.setSource (C:\Users\kl730355\Code\threat-intel\node_modules\rollup\dist\shared\rollup.js:10068:24)
    at ModuleLoader.addModuleSource (C:\Users\kl730355\Code\threat-intel\node_modules\rollup\dist\shared\rollup.js:18451:20)
    at ModuleLoader.fetchModule (C:\Users\kl730355\Code\threat-intel\node_modules\rollup\dist\shared\rollup.js:18507:9)
    at async Promise.all (index 0)

This does not seem to happen when I remove resolve from plugins, but that obviously introduces an unresolved dependencies issue

Reproduction

1. Run node scripts/setupTypeScript.js as suggested in docs
2. Add any typescript to src/main.ts
3. npm run build

Environment

• Windows 10
• Node 14.16.1

[lukasdiegelmann]

Do you have any solution for this error @zookini or maybe a workaround? If so please share. I need this error to be gone to properly make progress.

[VeselovAlex]

Try to add extensions: ['.ts', '.mjs', '.js', '.json', '.node'] to resolve options in rollup.config.js

resolve({
  browser: true,
  dedupe: ['svelte'],
  extensions: ['.ts', '.mjs', '.js', '.json', '.node']
}),

[KiKiKi-KiKi]

I was in the same error, when import .ts in .svelte file.

• "svelte": "^3.0.0"
• "rollup": "^2.3.4"
• "typescript": "^4.0.0"

// /src/Component.svelte
<script lang="ts">
  import { myScript } from './myScript';
</script>

=> [!] Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)

I resolve the error by add rootDir to rollup.config's typescript plugin.

rollup.config.js

export default {
  // …
  plugins: [
    // … 
    typescript({
      sourceMap: !production,
      inlineSources: !production,
+     rootDir: "./src",
    }),

But I can't decide its good way or not. Thank you 🙏

[Azarattum]

Can confirm the issue. This really is needed to be fixed!

[austinwitherspoon]

Having the same exact issue. Unfortunately adding rootDir: "./src" doesn't fix it for me.

Removing the resolve plugin as suggested at the top does seem to fix the issue, but I'm too new to javascript to understand the implications of doing that.
Edit: Nope, removing the resolve plugin makes this error go away but breaks svelte.