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fix: process style modules at the end during HMR #1257

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fix: process style modules at the end during HMR #1257

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17 changes: 15 additions & 2 deletions packages/vite-plugin-svelte/src/plugins/hot-update.js
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Expand Up @@ -81,16 +81,29 @@ export function hotUpdate(api) {
const svelteRequest = idParser(ctx.file, false, ctx.timestamp);
if (svelteRequest) {
const { modules } = ctx;
const svelteModules = [];
const svelteJsModules = [];

@ocavue ocavue Jan 7, 2026

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I'm not sure if svelteJsModules is a good variable name or not.

@ghost ghost Jan 7, 2026 •
edited by ghost
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its ok. technically could be a little confusing with .svelte.js files but they are not processed by the hot-update plugin at all so its fine.

an alternative would be to simply sort svelteModules instead of throwing them into 2 different buckets first. the number of modules in here is super low, usually its exactly 2, so perf really isn't an issue

@ocavue ocavue Jan 7, 2026

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an alternative would be to simply sort svelteModules

I feel that the following code is a bit hard to read.

svelteModules.sort((a, b) => {
    const numA = SVELTE_VIRTUAL_STYLE_ID_REGEX.test(a.id || '') ? 2 : 1;
    const numB = SVELTE_VIRTUAL_STYLE_ID_REGEX.test(b.id || '') ? 2 : 1;
    return numA - numB
})

@ghost ghost Jan 7, 2026 •
edited by ghost
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you don't need a custom comparator in this case, the css module id is constructed with a suffix, so svelteModules.sort() ensures that Foo.svelte?... comes after Foo.svelte.

edit: do'h, you need to map by id

svelteModules.sort((a,b)=> a.id > b.id ? 1 : a.id===b.id ? 0 : -1)

const svelteCssModules = [];
const nonSvelteModules = [];
for (const mod of modules) {
if (transformResultCache.has(mod.id)) {
svelteModules.push(mod);
if (mod.id && SVELTE_VIRTUAL_STYLE_ID_REGEX.test(mod.id)) {
svelteCssModules.push(mod);
} else {
svelteJsModules.push(mod);
}
} else {
nonSvelteModules.push(mod);
}
}

// Always process Svelte components first, then styles. This
// ensures that when we call
// `this.environment.transformRequest(mod.url)` later for
// style modules in this function, the Svelte components
// have already been processed and the cached styles are up
// to date.
const svelteModules = [...svelteJsModules, ...svelteCssModules];

if (svelteModules.length === 0) {
return; // nothing to do for us
}
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