feat: narrow page param types using matchers in $app/types (non-ambient.d.ts) by Stadly · Pull Request #15502 · sveltejs/kit

Stadly · 2026-03-06T23:28:11Z

Without this PR, page and layout params are always typed as string in $app/types, $app/state, and hooks, even when having matchers narrowing the type.

If we have this matcher and a route like src/routes/fruits/[page=fruit]:

// src/params/fruit.ts
import type { ParamMatcher } from '@sveltejs/kit';

export const match = ((param: string): param is ('apple' | 'orange') => {
	return param === 'apple' || param === 'orange';
}) satisfies ParamMatcher;

The parameter will now be typed as 'apple' | 'orange' instead of string in $app/types.

Note that this is similar to what we already have when working with page and layout params in src/routes/fruits/[page=fruit]/$types.js and in load functions. The exception is that in load functions and $types.js we know the exact route. In $app/state and hooks we don't so all parameters will be optional and their type a union of the type of all parameters with the same name.

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…t.d.ts)

changeset-bot · 2026-03-06T23:28:20Z

🦋 Changeset detected

Latest commit: bebc152

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

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.changeset/shaky-pandas-fold.md

elliott-with-the-longest-name-on-github

still going through, here are a few other comments

packages/kit/src/core/sync/write_types/test/app-types/matcher-test/no-matcher/[locale]/+page.js

packages/kit/src/core/sync/write_types/test/app-types/+page.js

…t.d.ts)

…y/kit into fix/narrow-param-types-to-matchers

elliott-with-the-longest-name-on-github · 2026-03-07T00:28:16Z

Pushed some refactors for performance (some of the stuff we were doing was O(n^2)) and to get rid of the ts-ignores we had in there

Should be good to go now, but I'll let another maintainer take a look at it since I changed a bunch of stuff

Thank you!

svelte-docs-bot · 2026-03-07T16:55:28Z

Preview: https://svelte-dev-git-preview-kit-15502-svelte.vercel.app/

packages/kit/src/core/sync/write_non_ambient.js

teemingc

LGTM. Just added a few comments to suggest making the if/elses easier to read

Stadly · 2026-03-09T12:04:28Z

Thanks, @teemingc! I think you're best equipped to respond to the comments, @elliott-with-the-longest-name-on-github, but let me know if you want me to do anything :)

Co-authored-by: Tee Ming <chewteeming01@gmail.com>

elliott-with-the-longest-name-on-github · 2026-03-09T18:35:37Z

@teemingc thank you! Should be addressed now

teemingc

Thanks!

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [@sveltejs/kit](https://svelte.dev) ([source](https://github.com/sveltejs/kit/tree/HEAD/packages/kit)) | [`2.53.4` → `2.55.0`](https://renovatebot.com/diffs/npm/@sveltejs%2fkit/2.53.4/2.55.0) | ![age](https://developer.mend.io/api/mc/badges/age/npm/@sveltejs%2fkit/2.55.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/@sveltejs%2fkit/2.53.4/2.55.0?slim=true) | --- ### Release Notes <details> <summary>sveltejs/kit (@sveltejs/kit)</summary> ### [`v2.55.0`](https://github.com/sveltejs/kit/blob/HEAD/packages/kit/CHANGELOG.md#2550) [Compare Source](https://github.com/sveltejs/kit/compare/@sveltejs/kit@2.54.0...@sveltejs/kit@2.55.0) ##### Minor Changes - feat: page and layout params with matchers are now type narrowed in `$app/types`, leading to better type safety when working with params in `$app/types`, `$app/state`, and hooks. ([#15502](sveltejs/kit#15502)) ### [`v2.54.0`](https://github.com/sveltejs/kit/blob/HEAD/packages/kit/CHANGELOG.md#2540) [Compare Source](https://github.com/sveltejs/kit/compare/@sveltejs/kit@2.53.4...@sveltejs/kit@2.54.0) ##### Minor Changes - feat: allow error boundaries to catch errors on the server ([#15308](sveltejs/kit#15308)) ##### Patch Changes - chore: upgrade `devalue` ([#15535](sveltejs/kit#15535)) - fix: don't wait for remote functions that are not awaited in the template ([#15280](sveltejs/kit#15280)) - feat: allow `resolve()` to accept pathnames with a search string and/or hash ([#15458](sveltejs/kit#15458)) - chore: remove deprecation warnings for `config.kit.files.*` options when validating the Svelte config file ([#15482](sveltejs/kit#15482)) - fix: handles form target attribute in remote form redirects ([#15457](sveltejs/kit#15457)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about these updates again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://forgejo.tail5a98.ts.net/gooilers123/monolith/pulls/45

fix: narrow page param types using matchers in $app/types (non-ambien…

db35574

…t.d.ts)

This was referenced Mar 6, 2026

fix: use MatcherParam for param matchers in $app/types (non-ambient.d.ts) Stadly/kit#1

Closed

Route params incorrectly typed in $app/state #15471

Closed

elliott-with-the-longest-name-on-github reviewed Mar 6, 2026

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Stadly force-pushed the fix/narrow-param-types-to-matchers branch from db35574 to bcab3d4 Compare March 6, 2026 23:41

fix: narrow page param types using matchers in $app/types (non-ambien…

cadf6de

…t.d.ts)

Stadly force-pushed the fix/narrow-param-types-to-matchers branch from bcab3d4 to cadf6de Compare March 6, 2026 23:50

elliott-with-the-longest-name-on-github added 2 commits March 6, 2026 17:25

chore: refactor for perf / correctness

9623b93

Merge branch 'fix/narrow-param-types-to-matchers' of github.com:Stadl…

7401fa2

…y/kit into fix/narrow-param-types-to-matchers

teemingc added the types / typescript label Mar 7, 2026

Merge branch 'main' into fix/narrow-param-types-to-matchers

e5cf0ce

fix eslint

720033a

Stadly changed the title ~~fix: narrow page param types using matchers in $app/types (non-ambient.d.ts)~~ feat: narrow page param types using matchers in $app/types (non-ambient.d.ts) Mar 7, 2026