fix: correctly configure module and noEmit tsconfig and jsconfig properties

[eltigerchino]

fixes #11023
fixes #9552

This PR fixes the errors found in tsconfig.json when scaffolding a typescript library project then running pnpm check.

Cannot write file '/src/lib/index.js' because it would overwrite input file.

This one is fixed by providing a index.ts file instead of .js in the example lib folder. EDIT: and adding noEmit to tsconfig

Option 'module' must be set to 'NodeNext' when option 'moduleResolution' is set to 'NodeNext'.

This one is fixed by adding the module: NodeNext to the library project tsconfig.json and jsconfig.json files. EDIT: setting module: bundler

Thanks to @hyunbinseo

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[dummdidumm]

This one is fixed by providing a index.ts file instead of .js in the example lib folder.

This won't help though if you're creating a library using JSDoc, you won't have a .ts file then. This is related to #9552 and the fix is something like this: #9552 (comment)

[eltigerchino]

This won't help though if you're creating a library using JSDoc, you won't have a .ts file then. This is related to #9552 and the fix is something like this: #9552 (comment)

Based on https://vitejs.dev/guide/features.html#transpile-only and https://www.typescriptlang.org/tsconfig#noEmit it would seem that noEmit is the right option here as per your comment in #9552 . I don't think it will affect Vite as they use esbuild instead of tsc to transpile to Javascript. This comment #9552 (comment) also suggests that other Vite based templates are using noEmit.

A bit off-topic: reading Vite's docs about tsc --noEmit makes me wonder if we should have type checking as part of the default npm build script before vite build.

[eltigerchino]

I've added noEmit to the templates but wonder what's the difference between putting it there and putting it in the generated one in .svelte-kit

[dummdidumm]

The generated one means that people updating SvelteKit get the fix, while putting it in create-svelte means people only get it when starting a new project (or they manually update their tsconfig).
I think in this instance it makes sense to have it in the generated tsconfig. I can't imagine a case where someone would use that same tsconfig to start a completely different build where the setting actually makes a difference. If Vite ignores it in all instances that matter, then it's probably fine. If we're paranoid/unsure if there couldn't be a case for not wanting it, then it should go into create-svelte like you did now.

[benmccann]

Setting noEmit in the generated file makes sense to me assuming we can do it just for JS projects.

I'm not sure about "moduleResolution": "NodeNext" though. Won't that start requiring users to have a .js extension? In SvelteKit 2, I think we'd like to set it to bundler and require TypeScript 5

[eltigerchino]

Setting noEmit in the generated file makes sense to me assuming we can do it just for JS projects.

I think it might be needed for TS projects too for whatever reason someone wants to have JS files in their TS project.

I'm not sure about "moduleResolution": "NodeNext" though. Won't that start requiring users to have a .js extension? In SvelteKit 2, I think we'd like to set it to bundler and require TypeScript 5

"moduleResolution": "NodeNext" is only being set for library projects at the moment. I don't much about what module and moduleResolution do.

EDIT: the generated file seems to be exporting moduleResolution: node which apparently means node10? https://www.typescriptlang.org/tsconfig#moduleResolution

[dummdidumm]

Yeah it is. While we're at it, I think it makes sense to set "moduleResolution": "bundler" in create-svelte for new projects, too. In SvelteKit 2 we can make that the generated default, but to not break things we shouldn't change that in 1.x

[eltigerchino]

While we're at it, I think it makes sense to set "moduleResolution": "bundler" in create-svelte for new projects, too.

Is that for all projects or just the library skeleton?

[benmccann]

"moduleResolution": "NodeNext" is only being set for library projects at the moment.

Ah, thanks. I missed that. That sounds good to me.

Is that for all projects or just the library skeleton?

I think libraries should be nodenext and applications should be bundler. (I usually see these written all lowercase as the TypeScript docs have them that way). nodenext is stricter and bundler is more permissive. It's best to be strict with libraries so that apps have the easiest time consuming them and permissive with apps so that they can consume the widest range of libraries

[hyunbinseo]

This one is fixed by providing a index.ts file instead of .js in the example lib folder.

This won't help though if you're creating a library using JSDoc, you won't have a .ts file then. This is related to #9552 and the fix is something like this: #9552 (comment)

The reason for proposing index.ts is to make it match the Skeleton project template.

As of create-svelte@5.2.0 there is this inconsistency.

src/lib	JSDoc	TypeScript
Library	index.js	index.js *
Skeleton	index.js	index.ts

The noEmit related issue is mentioned in the o.g. issue.

• Library project tsconfig errors - module value, overwrite input file #11023
• Svelte kit demo project tsconfig errors #9552 (comment)