Using typescript from external module results in parsing error

[vigenere23]

Describe the bug

Using typescript inside a Svelte component is fine, except when that file comes from an external module. This bug happens either when an external component using a Typescript file is imported and used or when the external Typescript file itself is directly imported and used.

Additional infos :

1. the web app project was setup using the provided script
2. the component library (external package) project was setup using a similar config, although such config is not provided by Svelte
3. the usage of the component library (external package) is done wither via npm link or by installing from npmjs.

Logs

See stacktraces

To Reproduce

1. clone app project and install dependencies : https://github.com/vigenere23/svelte-issue-5503
2. clone component library project and install dependencies : https://github.com/vigenere23/svelte-component-issue-5503
3. to locally link dependencies :
   1. inside component project, run yarn link
   2. inside app project, run yarn link svelte-component

Expected behavior

I would expect one of the following:

1. the library component would use an inlined compiled version of the used typescript file
2. the app project would directly import the typescript file and compile it itself, just like it does for local typescript files

Stacktraces

Stack trace for locally linking dependencies

bundles src/main.ts → public/build/bundle.js...
[!] Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
../gabio-design-svelte/src/utils/url.ts (1:7)
1: export type RelativeUrlResolver = (relativeUrl: string) => string
        ^
2:
3: export function resolveURL(
Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
  at error (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:5210:30)
  at Module.error (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:9725:16)
  at tryParse (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:9639:23)
  at Module.setSource (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:10036:30)
  at ModuleLoader.addModuleSource (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:18178:20)
  at ModuleLoader.fetchModule (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:18232:9)
  at async Promise.all (index 1)
  at ModuleLoader.fetchStaticDependencies (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:18256:34)
  at async Promise.all (index 0)
  at ModuleLoader.fetchModule (/home/gabio/Documents/projects/gabio-web-svelte/node_modules/rollup/dist/shared/rollup.js:18233:9)

Stack trace for remotely linking dependencies

src/main.ts → public/build/bundle.js...
[!] (plugin typescript) Error: Could not load /home/gabio/Documents/svelte-typescript-test/node_modules/@vigenere23/svelte-component/src/index.ts (imported by src/App.svelte): Debug Failure. False expression: Expected fileName to be present in command line
Error: Could not load /home/gabio/Documents/svelte-typescript-test/node_modules/@vigenere23/svelte-component/src/index.ts (imported by src/App.svelte): Debug Failure. False expression: Expected fileName to be present in command line
    at Object.getOutputFileNames (/home/gabio/Documents/svelte-typescript-test/node_modules/typescript/lib/typescript.js:94573:18)
    at findTypescriptOutput (/home/gabio/Documents/svelte-typescript-test/node_modules/@rollup/plugin-typescript/dist/index.js:391:33)
    at Object.load (/home/gabio/Documents/svelte-typescript-test/node_modules/@rollup/plugin-typescript/dist/index.js:592:28)

Information about your Svelte project:

• Browser: agnostic
• OS: Linux Ubuntu-based 20.04
• Svelte: 3.29.0 (latest from the time of writing)
• Rollup (from the given template)

Severity

It is currently blocking my project, and probably any other project that uses typescript component libraries. Starting from scratch in pain JS is possible but that's not the goal.

Additional context

More infos about the bug and temporary fixes here : sveltejs/component-template#29 (comment)

[stefanovualto]

@vigenere23 were you able to find a solution?

[vigenere23]

@stefanovualto Yes, my template has a working fix inspired from this discussion.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[dummdidumm]

Closing as this is unrelated to language-tools, this sounds more like a limitation with how the Rollup plugin handles files. In general, you should avoid having typescript files or Svelte files which require preprocessors in your node_modules and instead provide transpiled files along with type definitions. More info: https://github.com/sveltejs/language-tools/blob/master/docs/preprocessors/typescript.md#typing-components-authoring-packages