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fix: prevent deep_set crash on nullish nested values#15600

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elliott-with-the-longest-name-on-github merged 4 commits into
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RazinShafayet2007:fix/deep-set-nullish-clean
Apr 15, 2026
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fix: prevent deep_set crash on nullish nested values#15600
elliott-with-the-longest-name-on-github merged 4 commits into
sveltejs:mainfrom
RazinShafayet2007:fix/deep-set-nullish-clean

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@RazinShafayet2007

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Fixes #15599

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changeset-bot Bot commented Mar 25, 2026

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🦋 Changeset detected

Latest commit: f48283c

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

This PR includes changesets to release 1 package
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@sveltejs/kit Patch

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@RazinShafayet2007 RazinShafayet2007 force-pushed the fix/deep-set-nullish-clean branch 2 times, most recently from 74a5fd7 to 98521b2 Compare March 25, 2026 18:06
Comment thread packages/kit/src/runtime/form-utils.js Outdated
const inner = current[key];

if (exists && is_array !== Array.isArray(inner)) {
if (exists && inner != null && is_array !== Array.isArray(inner)) {

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We should probably add the null check after Object.hasOwn as a ternary -- then we can just check !exists or exists

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Done!

@RazinShafayet2007 RazinShafayet2007 force-pushed the fix/deep-set-nullish-clean branch from 209307e to 7d4b46a Compare April 8, 2026 05:16

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adjusted the tests a little and made a couple of drive-by fixes -- thank you!

@elliott-with-the-longest-name-on-github elliott-with-the-longest-name-on-github merged commit 2a5ad53 into sveltejs:main Apr 15, 2026
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@github-actions github-actions Bot mentioned this pull request Apr 15, 2026
@RazinShafayet2007 RazinShafayet2007 deleted the fix/deep-set-nullish-clean branch April 15, 2026 21:10
elliott-with-the-longest-name-on-github pushed a commit that referenced this pull request Apr 23, 2026
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
## @sveltejs/kit@2.58.0

### Minor Changes

- breaking: require `limit` in `requested` (as originally intended)
([#15739](#15739))


- feat: `RemoteQueryFunction` gains an optional third generic parameter
`Validated` (defaulting to `Input`) that represents the argument type
after schema validation/transformation
([#15739](#15739))


- breaking: `requested` now yields `{ arg, query }` entries instead of
the validated argument
([#15739](#15739))

### Patch Changes

- fix: allow `query().current`, `.error`, `.loading`, and `.ready` to
work in non-reactive contexts
([#15699](#15699))


- fix: prevent `deep_set` crash on nullish nested values
([#15600](#15600))


- fix: restore correct `RemoteFormFields` typing for nullable array
fields (e.g. when a schema uses `.default([])`), so `.as('checkbox')`
and friends work again
([#15723](#15723))


- fix: don't warn about removed SSI comments in `transformPageChunk`
([#15695](#15695))

Server-side include (SSI) directives like `<!--#include virtual="..."
-->` are HTML comments that are replaced by servers such as nginx.
Previously, removing them in `transformPageChunk` would trigger a false
positive warning about breaking Svelte's hydration. Since SSI comments
always start with `<!--#` and Svelte's hydration comments never do, they
can be safely excluded from the check.

- Change enhance function return type from void to MaybePromise<void>.
([#15710](#15710))


- fix: throw an error when `resolve` is called with an external URL
([#15733](#15733))


- fix: avoid FOUC for CSR-only pages by loading styles and fonts before
CSR starts ([#15718](#15718))


- fix: reset form result on redirect
([#15724](#15724))

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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deep_set crashes when setting a nested property on an existing key with value undefined or null

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