# `react-doctor/no-spread-props-over-defaults-clobbers-with-undefined`

Spread props over defaults can clobber with undefined

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

## Validate the diagnostic

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

Confirm the reported code matches `react-doctor/no-spread-props-over-defaults-clobbers-with-undefined`. 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

```ts
interface Props {
  width?: number;
}
const defaults = { width: 100 };
const Panel = (props: Props) => {
  const merged = { ...theme, ...defaults, ...props };
  return merged.width * 2;
};
```

### Corrected pattern

```ts
interface Props {
  width?: number;
}
const defaults = { width: 100 };
const Panel = (props: Props) => {
  const merged = { ...theme, ...defaults, ...props };
  return (merged.width ?? 100) * 2;
};
```

## 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.

````text
Fix every confirmed `react-doctor/no-spread-props-over-defaults-clobbers-with-undefined` diagnostic in the current repository.

Required change:
- An explicit undefined prop can overwrite a default. Reapply defaults with ?? at the merge or use site, or remove undefined keys before spreading props.

Reference transformation:

Before:
```ts
interface Props {
  width?: number;
}
const defaults = { width: 100 };
const Panel = (props: Props) => {
  const merged = { ...theme, ...defaults, ...props };
  return merged.width * 2;
};
```

After:
```ts
interface Props {
  width?: number;
}
const defaults = { width: 100 };
const Panel = (props: Props) => {
  const merged = { ...theme, ...defaults, ...props };
  return (merged.width ?? 100) * 2;
};
```

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.
- Confirm this rule is enabled for the project: `react`.

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.
````