# `react-doctor/no-direct-mutation-state`

Disallow mutating this.state directly in class components: use setState so React schedules a re-render.

- **Status:** Active
- **Category:** Correctness
- **Assessment:** Evidence-required risk
- **Required evidence:** source code
- **Default configuration:** Enabled
- **Default severity:** error
- **Scope:** All supported frameworks
- **Active when:** always (unless customRulesOnly=true)
- **Requirements:** react
- **Priority:** 47 (P3)
- **Source:** oxlint-plugin-react-doctor
- **Rule set:** oxlint-plugin-react-doctor 0.9.3 (prompt schema 2)
- **Documentation:** [Official documentation](https://oxc.rs/docs/guide/usage/linter/rules/react/no-direct-mutation-state.html)

## Validation prompt

Confirm the detector match and collect the required evidence before deciding whether an edit is warranted.

Fires on this.state.foo = value (or this.state = value outside the constructor) inside React class components: subclasses of React.Component / Component / PureComponent, or createReactClass factories. The mutation bypasses React's scheduler, so a subsequent setState() can silently overwrite it and no re-render is queued. False positive (non-trigger): constructor assignments (this.state = { foo: 'bar' } inside the constructor) are intentionally allowed.

## Evidence boundary

The diagnostic proves only that the detector's modeled source pattern matched. It does not prove runtime impact, product intent, rendered failure, or that one remediation is correct.

Establish the environment, explicit repository policy, relevant exceptions, and required rendered or runtime evidence before deciding the occurrence. This page’s Assessment and Required evidence fields define the review contract.

Default severity is registry metadata. Use the occurrence's JSON severity after repository configuration when ordering real findings.

Record one outcome:

- **Confirmed failure:** The required evidence establishes the violation.
- **Rejected:** A documented exception or false-positive predicate applies.
- **Needs evidence:** Named evidence can still be collected.
- **Unavailable:** Required evidence cannot be collected in this run.
- **Waived with evidence:** An authorized, scoped exception applies to an established failure.
- **Observation:** The review records an optional tradeoff without claiming a defect.

A waiver records its scope, authority, evidence, and review or expiry condition. It is not a pass or false positive.

## Fix prompt

Apply this candidate correction only after the required evidence confirms the risk.

Replace mutations with this.setState({ foo: nextValue }), or the updater form this.setState(prev => ({ foo: derive(prev.foo) })) when the next value depends on the previous one. Initialize defaults only in the constructor or via a class field (state = { foo: 'bar' }). Better, port the class to a function component with useState. See https://oxc.rs/docs/guide/usage/linter/rules/react/no-direct-mutation-state.html and https://react.dev/reference/react/Component#setstate

## Repository-wide copy prompt

Use this only for a repository-wide pass after validating each occurrence. For one occurrence, use the occurrence-level guidance above.

````text
Fix every confirmed `react-doctor/no-direct-mutation-state` diagnostic in the current repository.

Required change:
- Replace mutations with this.setState({ foo: nextValue }), or the updater form this.setState(prev => ({ foo: derive(prev.foo) })) when the next value depends on the previous one. Initialize defaults only in the constructor or via a class field (state = { foo: 'bar' }). Better, port the class to a function component with useState. See https://oxc.rs/docs/guide/usage/linter/rules/react/no-direct-mutation-state.html and https://react.dev/reference/react/Component#setstate.

Validation before editing:
Fires on this.state.foo = value (or this.state = value outside the constructor) inside React class components: subclasses of React.Component / Component / PureComponent, or createReactClass factories. The mutation bypasses React's scheduler, so a subsequent setState() can silently overwrite it and no re-render is queued. False positive (non-trigger): constructor assignments (this.state = { foo: 'bar' } inside the constructor) are intentionally allowed.

Constraints:
- 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: `always (unless customRulesOnly=true)`.

Assessment:
- Record detector evidence, applicability facts, assumptions, missing evidence, and the rule class for this occurrence.
- Return one outcome: Confirmed failure, Rejected, Needs evidence, Unavailable, Waived with evidence, or Observation.
- A waiver records the established failure, scope, authority, evidence, and review or expiry condition. It is not a pass or false positive.

Verification:
- Run focused tests for the changed behavior.
- Run React Doctor and confirm this diagnostic no longer appears from changed code.
- Run an unfiltered scan of the affected scope before claiming no cross-category regression.
- Report the files changed and any checks you could not run.
````