Promise Result Ignored

ID

javascript.promise_result_ignored

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

JavaScript

Tags

async, error-handling, reliability

Description

Reports an expression statement whose entire content is a bare call to an async function — no await, no .then()/.catch()/.finally() chain:

async function fetchData() { ... }

async function main() {
  fetchData();          // FLAW — returned Promise is dropped on the floor
}

Rationale

The Promise returned by an async call carries the call’s eventual completion and its rejection. Dropping it has two costs:

  • the caller cannot synchronise with the operation — the next line runs while fetchData is still in progress, and the program may exit before it completes,

  • any rejection becomes an unhandled rejection. Modern runtimes log a warning, browsers and Node may even crash the process; older code may silently mask the error.

Remediation

Pick the option that matches the intent:

// Wait for the Promise to settle.
await fetchData();

// Fire-and-forget but handle errors explicitly.
fetchData().catch((err) => log(err));

// Forward the Promise to a caller that does handle it.
return fetchData();

Notes

The rule fires only when the call is the entire value of an ExpressionStatement. Calls used in any larger expression — assignments, returns, arguments, .then() chains — are not reported because the result is being consumed.

The "is async" check resolves the called identifier to its declaration. Calls to functions whose async-ness is hidden behind a layer of indirection (e.g. a method that is async only at runtime via a factory) are not detected.

References