[intellix]

Fixes #9301

Since #9280, a child of a parent that can rerender has its props serialized. A prop like label={item.meta.label} compiles to _fnSignal((p0) => p0.meta.label, [item]), so the serializer wrote item, and SSR threw Q34 when item held a function (e.g. a TanStack column's accessorFn).

A wrapped signal that has computed without reading any reactive source can never change. It is now serialized as an identity sync fn over its current value ((p0)=>p0, [value]) instead of its function and captured args. It stays a WrappedSignal with the same effects, so resume is unchanged. Signals that are not yet computed, or that read a signal, store, or prop, serialize as before.

Tests

• component.spec.tsx: the issue's component (signal read in the parent body, deep prop over an object holding a function). Renders over SSR and client render, then rerenders the parent after resume.
• serdes.unit.ts: snapshot that only the value is serialized.

Both fail with Q34 without the fix.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Fixed server-side rendering failures when deeply nested props included an object containing a function.
  • Preserved nested prop values when child components read them alongside function-valued fields.
  • Ensured nested props backed by a store reflect store updates, and signal-driven content continues to update after user interactions.
  • Improved handling of wrapped signals with constant values while retaining existing behavior for signals whose results are functions.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3ab6dd0

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

This PR includes changesets to release 8 packages

Name	Type
@qwik.dev/core	Patch
@qwik.dev/devtools	Patch
eslint-plugin-qwik	Patch
@qwik.dev/mcp	Patch
@qwik.dev/react	Patch
@qwik.dev/router	Patch
@qwik.dev/utils	Patch
create-qwik	Patch

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• packages/qwik/src/core/tests/component.spec.tsx

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Walkthrough

The serializer now records the current value of qualifying wrapped signals instead of their original function and captured arguments. Added tests cover serialization and component behavior with nested props.

Changes: Wrapped-signal serialization

Layer / File(s)	Summary
Serialize constant wrapped signals packages/qwik/src/core/shared/serdes/serialize.ts	serializeWrappingFn checks whether a wrapped signal is valid and has no VNODE back-reference effects. If its untracked value is serializable, it serializes that value with an identity function. Other wrapped signals use the existing function-and-arguments path.
Serialization and deep-prop regression coverage packages/qwik/src/core/shared/serdes/serdes.unit.ts, packages/qwik/src/core/tests/component.spec.tsx, .changeset/constant-deep-prop-signal.md	Added serialization tests for source-free wrapped signals whose functions return a string or a function. Added component tests for nested props containing a function, local signal updates, and store-backed prop updates. Added a patch changeset describing the SSR case.

Priority: Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Possibly related issues

• QwikDev/qwik 9267 reports Q34 when an out-of-order segment serializes a derived signal over non-reactive data containing a function. This change covers source-free wrapped signals when their current value is serializable.

Suggested reviewers: maiieul, varixo

Merge Risk: Minimal · up to 3ab6d

The reported deep-prop rendering case is covered across server rendering and resume. No unresolved merge-blocking issue is established.

Security architecture risk: Low · up to 3ab6d

The change is narrowly scoped and preserves the existing serialized structure and resume mechanism. No introduced security vulnerability was established. Residual uncertainty concerns less common signal-forwarding behavior and application-specific data placed in client-visible state.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — Exposure is bounded to client-visible state for qualifying wrapped signals in applications using this serializer. The inspected change introduces no tenant-selection or privilege-granting mechanism, and no concrete sensitive producer was identified. Application-specific confidentiality consequences remain unverified.

Trust Boundaries and Controls

• observed — Constant folding is gated by computation state, absence of tracked sources, and serializability. Ordinary function-valued outputs fail the serializability gate and retain the original function-and-arguments path; the regression test explicitly covers this fallback.

Resilience and Maintainability Implications

• inferred — A resumed constant wrapper has different function/argument identity from its original representation. The unchanged prop-diff logic also compares unwrapped values, providing counterevidence to an immediate stale-value failure. Subscription ownership in every nested forwarding scenario is not established, but no security-relevant failure was demonstrated.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title names the primary change: source-free wrapped signals are now serialized as their current value. The raw summary confirms this change in serialize.ts, with supporting tests in serdes.unit.ts…
Linked Issues check		Issue #9301 requires SSR to avoid Q34 for a deep prop from a non-reactive object that contains a function. serializeWrappingFn now serializes a valid source-free wrapped signal as an identity functi…
Out of Scope Changes check		The serializer change directly implements issue #9301. The component and serdes tests verify the affected behavior and protect reactive deep props. The changeset documents the patch release for the af…

Full details: Title check

Explanation

The title names the primary change: source-free wrapped signals are now serialized as their current value. The raw summary confirms this change in serialize.ts, with supporting tests in serdes.unit.ts and component.spec.tsx. The title follows the conventional commit format and is specific enough for a teammate to understand the change.

Full details: Linked Issues check

Explanation

Issue #9301 requires SSR to avoid Q34 for a deep prop from a non-reactive object that contains a function. serializeWrappingFn now serializes a valid source-free wrapped signal as an identity function over its current serializable value. This avoids serializing the captured object and its function. The component tests cover the deep prop, parent rerender, child rerender, and reactive store behavior. The serdes tests cover value-only serialization and preservation of function-valued results.

Full details: Out of Scope Changes check

Explanation

The serializer change directly implements issue #9301. The component and serdes tests verify the affected behavior and protect reactive deep props. The changeset documents the patch release for the affected package. No unrelated change is demonstrated.

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@qwik.dev/core

npm i https://pkg.pr.new/QwikDev/qwik/@qwik.dev/core@9302

@qwik.dev/router

npm i https://pkg.pr.new/QwikDev/qwik/@qwik.dev/router@9302

@qwik.dev/utils

npm i https://pkg.pr.new/QwikDev/qwik/@qwik.dev/utils@9302

eslint-plugin-qwik

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create-qwik

npm i https://pkg.pr.new/QwikDev/qwik/create-qwik@9302

@qwik.dev/optimizer

npm i https://pkg.pr.new/QwikDev/qwik/@qwik.dev/optimizer@9302

@qwik.dev/devtools

npm i https://pkg.pr.new/QwikDev/qwik/@qwik.dev/devtools@9302

@qwik.dev/mcp

npm i https://pkg.pr.new/QwikDev/qwik/@qwik.dev/mcp@9302

commit: 3ab6dd0

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Actionable comments posted: 1

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Inline comments:
Review comments at @packages/qwik/src/core/shared/serdes/serialize.ts:
- Around line 1163-1166: Update the isConstantWrappedSignal handling to use the
function-and-args serialization path when its arguments are serializable, and
fall back to sending only $untrackedValue$ when they are not. Ensure the
fallback never passes an unserializable computed function through returnArg or
writeValue.

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• .changeset/constant-deep-prop-signal.md
• packages/qwik/src/core/shared/serdes/serdes.unit.ts
• packages/qwik/src/core/shared/serdes/serialize.ts
• packages/qwik/src/core/tests/component.spec.tsx

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[Varixo]

Could you add these tests?

it('should render a deep prop in a child that can rerender', async () => {
  const Counter = component$((props: { label: string }) => {
    const count = useSignal(0);
    if (count.value < 0) {
      return null;
    }
    return <button onClick$={() => count.value++}>{`${props.label}${count.value}`}</button>;
  });
  const Parent = component$(() => {
    const item = { meta: { label: 'hello' }, format: () => 'x' };
    return <Counter label={item.meta.label} />;
  });

  const { document } = await render(<Parent />, { debug });
  await trigger(document.body, 'button', 'click');
  expect(document.querySelector('button')!.textContent).toBe('hello1');
});

it('should still update a deep prop that reads a store', async () => {
  const Parent = component$(() => {
    const store = useStore({ label: 'a' });
    const item = { meta: store };
    return (
      <div>
        <button onClick$={() => (store.label = 'b')} />
        <DeepPropLabel label={item.meta.label} />
      </div>
    );
  });

  const { document } = await render(<Parent />, { debug });
  expect(document.querySelector('span')!.textContent).toBe('a');
  await trigger(document.body, 'button', 'click');
  expect(document.querySelector('span')!.textContent).toBe('b');
});

[intellix]

@Varixo Added both tests in 3ab6dd0. They run under SSR and client render. Without the fix, the rerendering-child test fails with Q34 under SSR. The store test passes either way, so it guards that reactive deep props keep updating.

[Varixo]

LGTM