Detect svelte.config.mjs for Deno

[yetdragon]

Describe the problem

SvelteKit currently doesn't officially support svelte.config.mjs, and I understand why (as discussed in #12331). However, this becomes a problem when using SvelteKit with Deno because, unlike Node.js, Deno recognizes a file as a module only if it has an .mjs extension. Due to this, the Svelte IntelliSense incorrectly shows an error:

Error in svelte.config.js

SyntaxError: Cannot use import statement outside a module (svelte)

This issue is similar to one faced by Vite, which was resolved by using vite.config.mjs.

Although, Deno is a very niche development runtime for SvelteKit, it would be nice to have support for it in SvelteKit.

Describe the proposed solution

Make SvelteKit detect svelte.config.mjs as a configuration file.

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

[marvinhagemeister]

An alternative solution would be to check for a deno.json or deno.jsonc file and treat the project as ESM by default. It's likely that there is some existing code that checks for package.json and for type: "module" that causes the problem in the first place. Extending that logic for Deno might be the best solution.

[dummdidumm]

What's speaking against adding type: "module" to the package.json? From what I understand it's irrelevant for Deno, but for local tooling it would then know that the file is ESM.

[yetdragon]

What's speaking against adding type: "module" to the package.json? From what I understand it's irrelevant for Deno, but for local tooling it would then know that the file is ESM.

This fixed the issue. I mistakenly assumed this as Deno-related problem but it seems not. I will close the issue. Sorry for bothering.