@studnicky/v8/delete-property

Reports delete object.property, optional-chain deletion, and Reflect.deleteProperty(object, key). With TypeScript type services, it permits a target only when every meaningful non-nullish type constituent has a string or number index signature, or is the bare object type. Those shapes make no fixed-property guarantee for deletion to violate. Without type services, every supported deletion is reported.

The exemption is evidence about the type contract, not a claim that deletion is free. Across 2,000,000 objects, deleting from a fixed-shape class instance made reads 9.6× slower (155.0 ms versus 16.2 ms); a dynamically keyed record was still 2.3× slower (49.0 ms versus 20.9 ms). Use an index-signature or bare-object deletion only when removal is the required operation.

Fixable: No · Options: No · Suggested severity: error

✗ Incorrect

class Session {
  public token = 'secret';

  public clear(): void {
    delete this.token;
  }
}

const account: { id: string; temporary: boolean } = { 'id': '1', 'temporary': true };
delete account.temporary;

✓ Correct

const cache: Record<string, string> = { 'token': 'secret' };
delete cache.token;

function removeMember(target: object): boolean {
  return Reflect.deleteProperty(target, 'temporary');
}