---
title: "async"
description: "Review promise-array ownership, effect timers, and request cancellation."
---

> Documentation Index
> Fetch the complete documentation index at: https://anydoctor.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# async

The Async doctor uses shared expression and lexical-binding facts. Its findings
are review inputs, not authorization to rewrite concurrency or request lifetimes.
All three checks use semantic revision 2 and report individual occurrences with
zero-based columns and full expression evidence ranges.

| Severity | Check | Supported observation |
| -------- | ----- | --------------------- |
| info | `fetch-calls-without-abortsignal` | Native fetch with known input/options that establish no caller cancellation signal |
| warning | `unawaited-async-map` | Known array map with an async callback and no supported consumer or ownership transfer |
| warning | `uncleared-settimeout-in-effect` | Native timer reached from a React effect with no supported matching cancellation in returned cleanup |

## What the checks establish

Fetch analysis recognizes global calls and immutable aliases, Request constructors,
known options, comments, static computed properties, and ordered object spreads.
An unknown Request or forwarded options can carry a signal, so the check abstains.
A later property can replace an earlier signal; null disconnects an inherited
Request signal, while undefined follows the platform's optional dictionary behavior.
Signal presence does not prove that the caller will abort. Cancellation and deadline
requirements differ across servers, extensions and UIs; no universal unmount fix
is prescribed.

Promise-array analysis distinguishes the actual result from its source container.
`Promise.all(tasks)` and `Promise.all([...tasks])` consume elements;
`Promise.all([tasks])`, `Promise.all([tasks.length])`, or awaiting `{task}` do not.
Aliases, returned arrays, supported local helpers and per-element awaits preserve
ownership. Returning an array transfers responsibility; it does not certify the
caller. Unrelated map methods and unresolved receivers or transfers abstain.
For sequential processing use an explicit loop with await inside; removing `async`
from a callback does not make its asynchronous operations sequential.

Timer analysis resolves React imports and native timer APIs, including aliases,
namespace/default React imports and qualified calls. Cleanup must be returned and
refer to the actual handle. Same-named bindings and uncalled helpers are insufficient.
Directly invoked local scheduling and cleanup helpers are supported. A timer
observation still needs a lifetime decision: some completion work is intentional.

## Limits and unavailable analysis

All checks need call analysis. Without it, they abstain and the report lists all
three checks as narrowed. There is no name-based fallback. An unavailable scan is
not a clean result, even when its numeric score is high.

The analysis is bounded: arbitrary interprocedural execution, cross-file wrappers,
custom thenables, monkey-patched globals, general property mutation and runtime type
inference are not interpreted. Array identity uses literals, declared array types
and supported array-producing chains. Unknown string-or-Request inputs may lose
useful fetch candidates. Conditional execution, cancellation through opaque
factories, and multiple outstanding timers in one mutable handle need manual review.
A supported consumer relationship is not proof of settlement on every runtime path.

Default diagnostic extension limits (`.mts`, `.cts`, `.cjs`), generated/test scope
and fixture-file exclusion remain separate from these repairs. Use the doctor for
supervised review; independent acceptance and broader precision evidence are still
needed before treating it as a trusted source of automatic fixes.

Source: https://anydoctor.dev/doctors/async/index.mdx