Difference between how Svelte and JS imports from node_modules are handled

Through #1048, I noticed there is a difference between how JS and Svelte files imported from node_modules are handled:

• Imports from node_modules that have no accompanying type definition (d.ts file) are marked as any which errors on strict mode (no implicit any). This means TS does not attempt to aquire the type structure from the node_modules package and also does not type-check it
• Svelte imports from node_modules are read and treated as a regular file inside the project. This means they don’t need a accompanying type definition and their types are aquired, which can be good or bad depending on the quality of the Svelte file. Some libraries like svelte-loading-spinners take advantage of this and provide TS-versions of Svelte files as types, which is dangerous.

I think in the long run it would be best to align with the behavior of TypeScript here. This would probably a breaking change to some users which do deep imports of Svelte files within libraries which don’t have a .svelte.d.ts next to them. I’m also not sure how to even achieve this as I thought this stuff is handled inside ts.resolveModuleName. As an intermediate step, we definetly need to stop type-checking stuff inside node_modules (also see #1100) @jasonlyu123 thoughts?

[dummdidumm]

The diagnostics you get from node_modules are from real TypeScript files. These files will be type-checked by TypeScript/tsc, too. You can try yourself by doing import { emit } from '@tauri-apps/api/event' in a .ts file and then running tsc --noEmit. There’s also an issue about this in the TypeScript repo, with the current conclusion that this is “works as designed”: https://github.com/microsoft/TypeScript/issues/40426. This sounds more like a misconfiguration of the build step of the library (why are .ts files deployed?) or a misuse of the library (avoid importing the .ts files).

[dummdidumm]

Yes. You could check .ts files with tsc --noEmit however. But that might produce some false positives, depending on whether or not you have named imports from Svelte files inside TS files.