# `react-doctor/no-mutating-array-method-on-prop-or-hook-result`

In-place array mutation on a prop or hook result

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

## Validate the diagnostic

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

Confirm the reported code matches `react-doctor/no-mutating-array-method-on-prop-or-hook-result`. 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
function useTrim(items) {
  const rows = useContext(RowsContext);
  useEffect(() => {
    return () => {
      rows.splice(0, 1);
    };
  }, [rows]);
}
```

### Corrected pattern

```ts
function useTrim() {
  const setRows = useContext(RowsDispatchContext);
  useEffect(() => {
    return () => {
      setRows((currentRows) => currentRows.slice(1));
    };
  }, [setRows]);
}
```

## 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-mutating-array-method-on-prop-or-hook-result` diagnostic in the current repository.

Required change:
- `sort`, `reverse`, and `splice` mutate in place, so calling them on a prop or hook result corrupts shared state. Use the immutable `toSorted`/`toReversed`/`toSpliced`, or copy the array first (`[...array].sort()`) when targeting pre-ES2023 runtimes.

Reference transformation:

Before:
```ts
function useTrim(items) {
  const rows = useContext(RowsContext);
  useEffect(() => {
    return () => {
      rows.splice(0, 1);
    };
  }, [rows]);
}
```

After:
```ts
function useTrim() {
  const setRows = useContext(RowsDispatchContext);
  useEffect(() => {
    return () => {
      setRows((currentRows) => currentRows.slice(1));
    };
  }, [setRows]);
}
```

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.
````