Tooling to prevent writing code in legacy mode

[wilsonowilson]

Describe the problem

I've been using Svelte 5 for a few weeks now and I love it!

As someone who's been writing in the legacy syntax for years now though, I occasionally slip up and use legacy APIs when creating components.

It's also a problem working with teammates who are new to Svelte 5, as they fallback constantly to legacy APIs, and we only catch them during code reviews.

Describe the proposed solution

I've searched and I'm not sure if it exists already, but isn't there some lint rule or editor setting that creates an error warning when writing components in the legacy syntax?

VSCode has a setting to highlight when a component is written in the legacy syntax, but AFAIK there's no way to enforce that components are written in runes mode.

On an aside, it's also mildly annoying that this feature defaults to legacy mode instead of runes mode.

Importance

would make my life easier

[adiguba]

Hello,

You can use runes: true on the compiler options : https://svelte.dev/docs/svelte/svelte-compiler#CompileOptions

Note that will impact external library, and could be set dynamically via Vite config.

[wilsonowilson]

@adiguba This is almost perfect.

• For this to work for our use case we'd need dynamicCompileOptions so we can use legacy deps.
• https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/config.md#dynamiccompileoptions
• but I can't find a way to use this in a sveltekit project?

[paoloricciuti]

• but I can't find a way to use this in a sveltekit project?

You can specify it in the svelte.config.js on kit.vitePlugin.dynamicCompileOption

Here's an example of how I did it on sveltelab.

[rodrigocfd]

You can use runes: true on the compiler options : https://svelte.dev/docs/svelte/svelte-compiler#CompileOptions

Note that will impact external library, and could be set dynamically via Vite config.

I have a Vite project (no SvelteKit), can you give an example of how to set this option?

[paoloricciuti]

You can use runes: true on the compiler options : https://svelte.dev/docs/svelte/svelte-compiler#CompileOptions
Note that will impact external library, and could be set dynamically via Vite config.

I have a Vite project (no SvelteKit), can you give an example of how to set this option?

The svelte config should work the same

[paoloricciuti]

Since this seem what the OP wanted I'm gonna close this issue, thanks for reporting