[GauBen]

Hi!

This is what I believe is a fix for the following runtime error:

TypeError: can't access property "f", signal is undefined

This happens in very simple scenarios, e.g.:

<script>
  const foo = $derived(await "foo");
</script>

<custom-element {foo}>Hello World!</custom-element>

Reproduction: https://svelte.dev/playground/274f0e1224f0440fba0d2a590cd402fb?version=latest

I noticed it happened because elements and custom elements do not produce the same code when async is at stake:

// Custom element, broken
$.template_effect(() => $.set_custom_element_data(custom_element, 'foo', $.get(foo)));

// HTML element, ok
$.template_effect(() => $.set_attribute(p, 'foo', $.get(foo)), void 0, void 0, [$$promises[0]]);

I tried to have the same sync/async/blockers parameters produced for $.set_custom_element_data

(It's fun to realize I'm probably the first person to combine async and custom elements)

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.
• If this PR changes code within packages/svelte/src, add a changeset (npx changeset).

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[pkg-svelte-dev]

Install the latest version of svelte from 7199b4b:

pnpm add https://pkg.svelte.dev/svelte/c/7199b4b276757d95ec8e2ca825af35b71441a846

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/svelte/pr/18661

Note

This PR is from a fork. A maintainer must approve approve each commit before it can be built and installed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 7199b4b

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

This PR includes changesets to release 1 package

Name	Type
svelte	Patch

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[dummdidumm]

thank you!