Promise.reject Without an Error

ID

javascript.prefer_promise_reject_errors

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

JavaScript

Tags

best-practice, reliability

Description

Reports Promise.reject(value) calls whose argument is not an Error instance — a string, number, null, an object literal, etc. Rejecting with a non-Error value loses the stack trace and breaks the standard instanceof Error discrimination in catch handlers.

Rationale

  • Without a stack trace, the catch handler has no clue where the rejection originated.

  • instanceof Error discrimination — common in centralized error middleware — silently fails for non-Error rejections.

  • Unhandled-rejection logs become much less informative (often just [object Object]).

This is the Promise sibling of javascript.no_throw_literal.

// Bad
return Promise.reject("not found");
return Promise.reject({ code: 404 });

Remediation

Reject with a real Error (or a domain-specific subclass).

// Good
return Promise.reject(new NotFoundError("not found", { code: 404 }));
return Promise.reject(new Error("not found"));

References