`react-doctor/no-arithmetic-on-optional-chained-operand`

Multiplicative math on optional-chained value can be NaN

Category: Bugs
Severity: warn
Source: oxlint-plugin-react-doctor
Framework: global
Enabled when: always
Default: Enabled

Validate the diagnostic

Confirm the reported code matches this rule before you edit it.

Confirm the reported code matches react-doctor/no-arithmetic-on-optional-chained-operand. Compare it with the Before example and verify the same API, framework, and execution context. Treat it as a false positive only when one of those conditions differs.

Compare the code

The corrected pattern shows a focused way to address the diagnostic.

Reported pattern

if (order.discount?.amount * quantity < minimumSubtotal) {
  showDiscountWarning();
}

Corrected pattern

const discount = order.discount?.amount;
if (discount !== undefined && discount * quantity < minimumSubtotal) {
  showDiscountWarning();
}

How to fix

Use the corrected pattern as a reference. Preserve behavior that the rule does not require you to change.

Copyable fix prompt

Copy this self-contained prompt into your coding agent after you confirm the diagnostic.

Fix every confirmed react-doctor/no-arithmetic-on-optional-chained-operand diagnostic in the current repository. Required change: - An optional chain is undefined when it short-circuits, so *///% on it produces NaN, which silently corrupts formatting and comparisons. Provide a ?? fallback or guard the chain root before the arithmetic.

Reference transformation:Before:

if (order.discount?.amount * quantity < minimumSubtotal) {
  showDiscountWarning();
}

After:

const discount = order.discount?.amount;
if (discount !== undefined && discount * quantity < minimumSubtotal) {
  showDiscountWarning();
}

Constraints: - Confirm the reported code matches the Before pattern. - Make the smallest change that fixes the root cause. - Preserve behavior and interfaces unrelated to this diagnostic. - Reuse existing project components, utilities, and conventions. - Do not introduce render-phase side effects, render-phase state updates, or Hooks rule violations. - Adapt identifiers and framework details instead of copying blindly. - Do not disable the rule or suppress matching code. Verification: - Run focused tests for the changed behavior. - Run React Doctor and confirm this diagnostic no longer appears. - Report the files changed and any checks you could not run.

More Bugs rules from the rules reference:

react-doctor/no-array-find-result-member-access-without-guard: Unguarded member access on find() result
react-doctor/no-array-index-as-key: Use a stable unique identifier: `key={item.id}` or `key={item.slug}` — index keys break on reorder/filter
react-doctor/no-array-index-deref-without-bounds-or-empty-guard: Array index result dereferenced without a guard
react-doctor/no-async-effect-callback: Async effect callback
react-doctor/no-async-event-handler-without-reentry-guard: Async mutating handler without re-entry guard

react-doctor/no-arithmetic-on-optional-chained-operand