fix(async-queuer): use nullish check in #tick to handle falsy queue items by simonmeyerrr · Pull Request #201 · TanStack/pacer

simonmeyerrr · 2026-04-17T13:59:23Z

🎯 Changes

Fixes #200

AsyncQueuer#tick() used if (!nextItem) to check whether the queue was empty, which caused falsy items (0, "", false) to be silently skipped. Changed to if (nextItem === undefined) to match the sentinel already used by getNextItem() and execute().

Added tests verifying that items with values 0, "", and false are processed correctly.

The issue is actually deeper than this, but this PR aim to make the minimal fix for this cases. A better fix would be to refactor some methods signature from TValue | undefined to something like { hasItem: false } | { hasItem: true, item: TValue } in order to also allow undefined as a value (as nothing in addItem or TValue prevent having an undefined item), but it would require a major version change.

Note: I didn't add a test for null, because this value makes other part of the code crash (priority computing) which should be fixed in other issues/PRs.

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

Bug Fixes

Fixed an issue where queued items with falsy values (0, empty string, false) were incorrectly excluded from processing, ensuring they are now properly handled and processed as intended.

Tests

Added test coverage for falsy item handling to verify correct processing of items with falsy values.

…tems

coderabbitai · 2026-04-17T14:00:02Z

📝 Walkthrough

Walkthrough

This pull request fixes AsyncQueuer#tick to properly handle falsy item values. The loop break condition was changed from a generic falsy check to an explicit undefined check, allowing items with values like 0, false, and '' to proceed through processing instead of being silently excluded.

Changes

Cohort / File(s)	Summary
Falsy Item Handling Fix `packages/pacer/src/async-queuer.ts`, `packages/pacer/tests/async-queuer.test.ts`	Fixed loop condition to explicitly check for `undefined` instead of falsy values, and added comprehensive test suite with three cases validating correct handling of `0`, `''`, and `false` items during queue processing.
Changelog `.changeset/young-planes-clap.md`	Documented patch-level fix for `@tanstack/pacer` addressing falsy item exclusion in `AsyncQueuer#tick`.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Once falsy values were cast away,
But now they hop and skip and play,
In AsyncQueuer's gentle queue,
Zeros, empties—all ring true! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and specifically describes the main change: using a nullish check instead of a falsy check to handle falsy queue items, which is the core fix in this PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The PR description fully addresses all required template sections with clear details, complete checklist, and comprehensive context.

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coderabbitai

🧹 Nitpick comments (1)

packages/pacer/tests/async-queuer.test.ts (1)
1099-1163: Good targeted coverage for the fix.

All three JS falsy primitives (0, '', false) are exercised with mixed orderings, and both processed order and successCount are asserted — this locks in the regression well.

Optional: consider also adding null and NaN cases for completeness (both are falsy; null !== undefined so they should also now pass through correctly). Not required for this patch.
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@packages/pacer/tests/async-queuer.test.ts` around lines 1099 - 1163, Add
tests to cover the remaining falsy values null and NaN: create new it blocks
that instantiate AsyncQueuer<T> (use AsyncQueuer<any> for NaN/null), push null
and NaN items via addItem in mixed order with truthy values, call start() and
advance timers with vi.advanceTimersByTimeAsync, then assert the processed array
contains the original values in order and asyncQueuer.store.state.successCount
equals the number of items; reference AsyncQueuer, addItem, start,
store.state.successCount and vi.advanceTimersByTimeAsync when locating where to
add these tests.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@packages/pacer/tests/async-queuer.test.ts`:
- Around line 1099-1163: Add tests to cover the remaining falsy values null and
NaN: create new it blocks that instantiate AsyncQueuer<T> (use AsyncQueuer<any>
for NaN/null), push null and NaN items via addItem in mixed order with truthy
values, call start() and advance timers with vi.advanceTimersByTimeAsync, then
assert the processed array contains the original values in order and
asyncQueuer.store.state.successCount equals the number of items; reference
AsyncQueuer, addItem, start, store.state.successCount and
vi.advanceTimersByTimeAsync when locating where to add these tests.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 4978d571-e33c-4562-a615-b2f695d26dcf

📥 Commits

Reviewing files that changed from the base of the PR and between afc958f and b2e8e24.

📒 Files selected for processing (3)

.changeset/young-planes-clap.md
packages/pacer/src/async-queuer.ts
packages/pacer/tests/async-queuer.test.ts

Copilot

Pull request overview

Fixes TanStack/pacer issue #200 by ensuring AsyncQueuer#tick() doesn’t treat falsy queued items as “no item”, so values like 0, "", and false are processed instead of silently skipped.

Changes:

Changed #tick()’s queue-empty check from a falsy check to an explicit undefined sentinel check.
Added tests covering processing of falsy items (0, "", false).
Added a changeset for a patch release.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/pacer/src/async-queuer.ts	Updates `#tick()` to stop only when the next item is `undefined`, not when it’s merely falsy.
packages/pacer/tests/async-queuer.test.ts	Adds regression tests ensuring falsy items are processed.
.changeset/young-planes-clap.md	Declares a patch release for the falsy-item handling fix.

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simonmeyerrr · 2026-08-06T10:06:59Z

🧹 Nitpick comments (1)

Skipping null here, because it still blows up in priority handling on add ((item as any).priority), which is a separate issue. 0/""/false already lock the #tick sentinel fix. NaN isn’t needed for this patch.

KevinVandy · 2026-08-07T02:09:10Z

gave you co-auther credit in a larger PR that fixed this and even more issues at all once

simonmeyerrr added 2 commits April 17, 2026 15:42

fix(async-queuer): use nullish check in #tick to handle falsy queue i…

aaf562e

…tems

chore: add changeset

b2e8e24

coderabbitai Bot reviewed Apr 17, 2026

View reviewed changes

Merge branch 'main' into fix-async-queuer-falsy-items

91b5be4

Copilot AI lite review requested due to automatic review settings August 6, 2026 09:46

Copilot started reviewing on behalf of simonmeyerrr August 6, 2026 09:47 View session

Copilot AI reviewed Aug 6, 2026

View reviewed changes

Comment thread packages/pacer/src/async-queuer.ts

Comment thread packages/pacer/tests/async-queuer.test.ts

KevinVandy mentioned this pull request Aug 6, 2026

fix: falsy queue items, AsyncRetryer memory leak, wait bypass, and Awaited return types #246

Merged

KevinVandy closed this Aug 7, 2026

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fix(async-queuer): use nullish check in #tick to handle falsy queue items - #201

fix(async-queuer): use nullish check in #tick to handle falsy queue items#201
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simonmeyerrr:fix-async-queuer-falsy-items

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