feat(core): defer AsyncSignal errors during render#8757
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🦋 Changeset detectedLatest commit: c40e4b6 The changes in this PR will be included in the next version bump. This PR includes changesets to release 5 packages
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Varixo
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Jun 21, 2026
maiieul
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Jun 21, 2026
| Read `.value` when you need the result. If the result is not ready yet, that part of the UI can wait and a [`<Suspense>`](/docs/labs/suspense/index.mdx) boundary can show fallback UI. | ||
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| Note: If the function errored, reading from `.value` will throw the error. This is intentional, so you can handle errors with a `<ErrorBoundary>`. To avoid this, check `.error` before reading `.value`. | ||
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Pull request overview
This PR changes AsyncSignal error semantics during component rendering so that reading an errored async signal’s .value can be deferred until after render, allowing patterns like {signal.value && ...} and {signal.error && ...} without .value throwing mid-render.
Changes:
- Add render-only error deferral tracking to the invoke context and enable it during
executeComponent(). - Defer
AsyncSignalImpl.untrackedValuethrowing during a render and rethrow after render if.errorwas not read. - Update API/runtime docs and add a regression test for the “read
.valuethen.error” render pattern, plus a changeset.
Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| packages/qwik/src/core/use/use-core.ts | Adds per-render context field to track deferred async-signal errors. |
| packages/qwik/src/core/shared/component-execution.ts | Enables/reset tracking during component execution and rethrows unread async-signal errors post-render. |
| packages/qwik/src/core/reactive-primitives/impl/async-signal-impl.ts | Defers throwing from .value during render and marks .error reads as handled. |
| packages/qwik/src/core/reactive-primitives/signal.public.ts | Documents the new render-only deferred-throw behavior for AsyncSignal. |
| packages/qwik/src/core/tests/use-async.spec.tsx | Adds a test ensuring separate .value/.error reads in render don’t throw. |
| packages/docs/src/routes/docs/(qwik)/core/state/index.mdx | Updates state docs around useAsync$() error behavior. |
| packages/docs/src/routes/api/qwik/index.mdx | Updates API docs text for AsyncSignal to mention render deferral. |
| packages/docs/src/routes/api/qwik/api.json | Regenerates API docs JSON content to include the updated AsyncSignal docs. |
| .changeset/async-signal-defer-error-read.md | Declares a minor release for the new AsyncSignal render behavior. |
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| Read `.value` when you need the result. If the result is not ready yet, that part of the UI can wait and a [`<Suspense>`](/docs/labs/suspense/index.mdx) boundary can show fallback UI. | ||
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| Note: If the function errored, reading from `.value` will throw the error. This is intentional, so you can handle errors with a `<ErrorBoundary>`. To avoid this, check `.error` before reading `.value`. |
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| it('does not throw when .value and .error are read separately in a render', async () => { | ||
| const Counter = component$(() => { | ||
| const doubleCount = useAsync$(() => Promise.reject(new Error('boom'))); | ||
| // Reading .value first must not throw, because the render also handles .error. | ||
| const value = doubleCount.value; | ||
| const error = doubleCount.error; | ||
| return <div>{error ? `error: ${error.message}` : value}</div>; | ||
| }); | ||
| let threw = false; | ||
| let container; | ||
| try { | ||
| ({ container } = await render(<Counter />, { debug })); | ||
| } catch { | ||
| threw = true; | ||
| } | ||
| // Reading .value of the errored signal did not throw, because .error was also read. | ||
| expect(threw).toBe(false); | ||
| expect(container!.element.querySelector('div')?.textContent).toBe('error: boom'); | ||
| }); | ||
| }); |
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this allows writing
Note that setting error does not clear .value so the stale value can still be shown.