PR: UppyContextProvider.svelte generates https://svelte.dev/e/state_referenced_locally warning

[Alexander-Jordan]

Update UppyContextProvider.svelte: : use $derived() instead of $state() when dealing with $props() value since it's reactive, to avoid https://svelte.dev/e/state_referenced_locally warning.

Issue: #6140

[changeset-bot]

🦋 Changeset detected

Latest commit: 39c347b

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

This PR includes changesets to release 1 package

Name	Type
@uppy/svelte	Patch

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[Murderlon]

Thanks for making a PR immediately. Did you run yarn build && yarn workspace example-sveltekit dev to confirm yourself it works as expected?

[Alexander-Jordan]

Thanks for making a PR immediately. Did you run yarn build && yarn workspace example-sveltekit dev to confirm yourself it works as expected?

Yes, now I did that, and I found that the warning was transferred down to line 43:

setContext(UppyContextKey, contextValue)

So I fixed it now and tested it as you described, and it works well :)

[Copilot]

Pull request overview

This PR attempts to fix a Svelte 5 state_referenced_locally warning in UppyContextProvider.svelte by wrapping the uppy prop value in an IIFE when assigning it to the reactive $state object.

Changes:

• Modified how the uppy prop is assigned within the $state object using an IIFE pattern
• Added changeset documenting the fix

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/@uppy/svelte/src/lib/components/headless/UppyContextProvider.svelte	Modified uppy assignment in $state object to use IIFE pattern
.changeset/nice-jeans-sniff.md	Added changeset documenting the fix for capturing initial value of uppy

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[Copilot]

The IIFE pattern (() => uppy)() is functionally equivalent to just uppy - it still captures only the initial value and doesn't maintain reactivity. To properly track changes to the uppy prop from $props(), you should use $derived(uppy) instead: uppy: $derived(uppy). This will ensure the contextValue.uppy updates when the prop changes.

Suggested change

	uppy: (() => uppy)(),
	uppy: $derived(uppy),

[Alexander-Jordan]

$derived() can't be used this way, and yes this works as before but without the warning

[Murderlon]

I'm worried Copilot is correct and the only reason you didn't get a warning anymore is because the build linter no longer matches on this code usage, which wouldn't mean this is actually fixed.

I would find it very odd if using a IIFE like this inside state is a Svelte best practice.

[Alexander-Jordan]

Hmm, I had a thought about it again, and as you say even if I get rid of the warning, technically the issue is still there...

So I tried another method: separating status and progress props so they can be declared as $state()'s, and then instead used getters/setters to get the reactive values (and I didn't give the uppy prop a setter, since it is read-only).

Honestly experimenting a lot here, I think these warnings are a bit vaguely explained in the svelte docs.

Let me know what you think about it 👍🏻

[Murderlon]

I tried reproducing this error on the main branch and I can't get it to show up? Do you have a reproducible example?