Fix searchParams.set duplicate updates by jiyujie2006 · Pull Request #18336 · sveltejs/svelte

jiyujie2006 · 2026-05-31T07:41:21Z

Summary

detect SvelteURLSearchParams#set changes by comparing duplicate value lists instead of joined strings
update reactive subscribers when duplicate params collapse to a single value with the same concatenated text
cover both SvelteURLSearchParams and SvelteURL.searchParams synchronization

Tests

pnpm exec vitest run packages/svelte/src/reactivity/url-search-params.test.ts -t "URLSearchParams.set updates when duplicate values collapse to the same joined string"
pnpm exec vitest run packages/svelte/src/reactivity/url-search-params.test.ts packages/svelte/src/reactivity/url.test.ts

changeset-bot · 2026-05-31T07:41:25Z

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Latest commit: a4f62cb

The changes in this PR will be included in the next version bump.

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Rich-Harris · 2026-05-31T15:10:05Z

 	 */
 	set(name, value) {
-		var previous = super.getAll(name).join('');
+		var previous = super.getAll(name);


Suggested change

var previous = super.getAll(name);

var previous = super.getAll(name).join(',');

I think keeping the element-wise comparison avoids another collision case: new URLSearchParams('a=a&a=b') followed by set('a', 'a,b') changes the query string to a=a%2Cb, but both sides of join(',') are a,b. I added a regression test for that case in cb2d87a.

Ah, silly me — I thought the comma would be encoded in that case

Rich-Harris · 2026-05-31T15:10:21Z

+		var current = super.getAll(name);
+		if (previous.length !== current.length || previous.some((value, i) => value !== current[i])) {


Suggested change

var current = super.getAll(name);

if (previous.length !== current.length || previous.some((value, i) => value !== current[i])) {

if (previous !== super.getAll(name).join(',')) {

Same concern here: the comma-joined comparison would miss the a=a&a=b -> a=a%2Cb transition. The added test covers that edge case, so I kept the element-wise comparison.

Rich-Harris

Thanks — I think we can fix this more simply by just joining on "," instead of the empty string?

Rich-Harris

thank you!

This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.56.1 ### Patch Changes - fix: error at compile time on duplicate snippet/declaration tag definitions ([#18351](#18351)) - fix: parse declaration tag contents more robustly ([#18353](#18353)) - fix: correctly transform references to earlier declarators in a declaration tag (e.g. `{let a = $state(0), b = $derived(a * 2)}`) ([#18348](#18348)) - fix: avoid spurious `state_referenced_locally` warnings for `$derived` declarations in declaration tags ([#18348](#18348)) - fix: tolerate whitespace before `let`/`const` in declaration tags ([#18348](#18348)) - fix: prevent infinite loop when a tag's expression ends with a trailing `/` at the end of the input ([#18350](#18350)) - fix: more robust parsing of declaration tags with regards to `type` ([#18330](#18330)) - fix: preserve newlines in spread input values when the `type` attribute is applied after `value` ([#18345](#18345)) - fix: update `SvelteURLSearchParams` when setting duplicate keys to the same joined value ([#18336](#18336)) - fix: check references for blockers on server, too ([#18352](#18352)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [svelte](https://svelte.dev) ([source](https://github.com/sveltejs/svelte/tree/HEAD/packages/svelte)) | [`5.56.0` → `5.56.1`](https://renovatebot.com/diffs/npm/svelte/5.56.0/5.56.1) | ![age](https://developer.mend.io/api/mc/badges/age/npm/svelte/5.56.1?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/svelte/5.56.0/5.56.1?slim=true) | --- ### Release Notes <details> <summary>sveltejs/svelte (svelte)</summary> ### [`v5.56.1`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#5561) [Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.56.0...svelte@5.56.1) ##### Patch Changes - fix: error at compile time on duplicate snippet/declaration tag definitions ([#18351](sveltejs/svelte#18351)) - fix: parse declaration tag contents more robustly ([#18353](sveltejs/svelte#18353)) - fix: correctly transform references to earlier declarators in a declaration tag (e.g. `{let a = $state(0), b = $derived(a * 2)}`) ([#18348](sveltejs/svelte#18348)) - fix: avoid spurious `state_referenced_locally` warnings for `$derived` declarations in declaration tags ([#18348](sveltejs/svelte#18348)) - fix: tolerate whitespace before `let`/`const` in declaration tags ([#18348](sveltejs/svelte#18348)) - fix: prevent infinite loop when a tag's expression ends with a trailing `/` at the end of the input ([#18350](sveltejs/svelte#18350)) - fix: more robust parsing of declaration tags with regards to `type` ([#18330](sveltejs/svelte#18330)) - fix: preserve newlines in spread input values when the `type` attribute is applied after `value` ([#18345](sveltejs/svelte#18345)) - fix: update `SvelteURLSearchParams` when setting duplicate keys to the same joined value ([#18336](sveltejs/svelte#18336)) - fix: check references for blockers on server, too ([#18352](sveltejs/svelte#18352)) </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - At any time (no schedule defined) - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled because a matching PR was automerged previously. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).  Co-authored-by: huskas-2189 <huskas-2189@noreply.codeberg.org> Reviewed-on: https://codeberg.org/huskas-2189/Bookmark/pulls/82

Fix search params duplicate set updates

d26ddf4

Add search params duplicate update changeset

b65de1a

Rich-Harris reviewed May 31, 2026

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Comment thread .changeset/search-params-duplicate-set.md Outdated

Update .changeset/search-params-duplicate-set.md

add8d3f

Rich-Harris reviewed May 31, 2026

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Cover comma-joined duplicate search params

cb2d87a

Rich-Harris approved these changes May 31, 2026

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Merge branch 'main' into fix-search-params-set-duplicates

a4f62cb

Rich-Harris merged commit 2f6307a into sveltejs:main May 31, 2026
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github-actions Bot mentioned this pull request May 31, 2026

Version Packages #18346

Merged

github-actions Bot mentioned this pull request Jun 2, 2026

Upgrade Svelte submodule to 5.56.1 baseballyama/rsvelte#639

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Fix searchParams.set duplicate updates#18336

Fix searchParams.set duplicate updates#18336
Rich-Harris merged 5 commits into
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jiyujie2006:fix-search-params-set-duplicates

jiyujie2006 commented May 31, 2026

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	var previous = super.getAll(name);
	var previous = super.getAll(name).join(',');

		var current = super.getAll(name);
		if (previous.length !== current.length \|\| previous.some((value, i) => value !== current[i])) {

	var current = super.getAll(name);
	if (previous.length !== current.length \|\| previous.some((value, i) => value !== current[i])) {
	if (previous !== super.getAll(name).join(',')) {

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jiyujie2006 commented May 31, 2026

Summary

Tests

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changeset-bot Bot commented May 31, 2026 •

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