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feat: reduce number of js updates when editing component css #26

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Merged
merged 2 commits into from
Apr 5, 2021
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feat: reduce number of js updates when editing component css #26

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dc7f7be
feat: reduce number of js updates when editing component css
dominikg Apr 5, 2021
0504907
add changeset
dominikg Apr 5, 2021
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5 changes: 5 additions & 0 deletions .changeset/flat-books-kick.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'@sveltejs/vite-plugin-svelte': minor
---

improved css hmr
20 changes: 20 additions & 0 deletions packages/vite-plugin-svelte/src/utils/preprocess.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,22 @@ export function createVitePreprocessorGroup(
} as PreprocessorGroup;
}

/**
* this appends a *{} rule to component styles to force the svelte compiler to add style classes to all nodes
* That means adding/removing class rules from <style> node won't trigger js updates as the scope classes are not changed
*
* only used during dev with enabled css hmr
*/
function createInjectScopeEverythingRulePreprocessorGroup(): PreprocessorGroup {
return {
style({ content }) {
return {
code: `${content} *{}`
};
}
};
}

export function buildExtraPreprocessors(options: ResolvedOptions, config: ResolvedConfig) {
const extraPreprocessors = [];
if (options.useVitePreprocess) {
Expand All @@ -77,5 +93,9 @@ export function buildExtraPreprocessors(options: ResolvedOptions, config: Resolv
);
}

if (options.hot && !options.disableCssHmr) {
extraPreprocessors.push(createInjectScopeEverythingRulePreprocessorGroup());
}

return extraPreprocessors;
}