Provide an option to exclude files from HMR

[IanVS]

Describe the problem

In the storybook vite builder, we have a problem with svelte stories not correctly reloading when changes are made to files. I don't completely understand what's going on, but story files are watched by the manager webpack so that it can HMR the list of files, but that makes them incompatible for vite HMR, it seems. We had the same problem with react stories, and the solution was to exclude stories from HMR, allowing the page to reload instead when changes are made.

However, it seems there's no such option for svelte to control when HMR happens. It's only on or off, as far as I can tell.

Describe the proposed solution

It would be great if you could support an include/exclude set of globs, much like rollup transform plugins or @vitejs/plugin-react: https://github.com/vitejs/vite/tree/main/packages/plugin-react#filter-which-files-use-fast-refresh

Alternatives considered

I can turn off HMR entirely for svelte projects, but that doesn't seem like a great option. HMR is working just fine when editing components, just not stories.

Importance

would make my life the life of storybook users easier

[dominikg]

As far as i am aware storybook is not going to support authoring stories in svelte format going forward, and focuses on their own component story format (csf) instead.

So i'm not really sure how csf stories would end up being processed by vite-plugin-svelte.

As a workaround you could create 2 instances of vite-plugin-svelte that operate on disjunct sets with include/exclude:

const storyPattern = "**/*.story.svelte";
export default {
  plugins:[
    svelte({exclude: storyPattern}),
    {
      ...svelte({include: storyPattern, hot: false}), 
      name: "vite-plugin-svelte-stories" // avoid 2 plugin instances with same name
    }
  ]
}

[IanVS]

Thanks for the workaround suggestion. That looks like it will work.

It sounds like it's a bit uncertain what will happen in storybook 7.0, but I want to make sure everything works correctly in 6.x.

[bluwy]

If the workaround works, I think it is the solution instead of adding another option for this case, as include and exclude options are meant for this usecase.