`react-doctor/zustand-no-mutating-state`

Zustand state mutated in place

Category: Bugs
Severity: error
Source: oxlint-plugin-react-doctor
Framework: global
Enabled when: react, zustand, zustand:1
Default: Enabled

Validate the diagnostic

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

Confirm the reported code matches react-doctor/zustand-no-mutating-state. 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

import { create } from "zustand";

interface Todo {
  id: string;
}

interface TodoStore {
  todos: Todo[];
  addTodo: (todo: Todo) => void;
}

const useTodoStore = create<TodoStore>((set) => ({
  todos: [],
  addTodo: (todo) =>
    set((state) => {
      state.todos.push(todo);
      return { todos: state.todos };
    }),
}));

Corrected pattern

import { create } from "zustand";

interface Todo {
  id: string;
}

interface TodoStore {
  todos: Todo[];
  addTodo: (todo: Todo) => void;
}

const useTodoStore = create<TodoStore>((set) => ({
  todos: [],
  addTodo: (todo) =>
    set((state) => ({
      todos: [...state.todos, todo],
    })),
}));

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/zustand-no-mutating-state diagnostic in the current repository. Required change: - Create a new object, array, Map, or Set before passing the updated value to Zustand.

Reference transformation:Before:

import { create } from "zustand";

interface Todo {
  id: string;
}

interface TodoStore {
  todos: Todo[];
  addTodo: (todo: Todo) => void;
}

const useTodoStore = create<TodoStore>((set) => ({
  todos: [],
  addTodo: (todo) =>
    set((state) => {
      state.todos.push(todo);
      return { todos: state.todos };
    }),
}));

After:

import { create } from "zustand";

interface Todo {
  id: string;
}

interface TodoStore {
  todos: Todo[];
  addTodo: (todo: Todo) => void;
}

const useTodoStore = create<TodoStore>((set) => ({
  todos: [],
  addTodo: (todo) =>
    set((state) => ({
      todos: [...state.todos, todo],
    })),
}));

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, zustand, zustand:1. 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/zustand-no-whole-store-destructure: Whole Zustand store subscribed during render
react-doctor/activity-wraps-effect-heavy-subtree: Audit the `<Activity>` subtree: every hide/show cycle tears down and recreates every `useEffect`/`useLayoutEffect` inside, so move subscriptions and effect-driven setState chains outside the boundary or pre-resolve the data above it.
react-doctor/button-has-type: Set type="button" (or "submit"/"reset") explicitly on every <button> so it never defaults to submit.
react-doctor/checked-requires-onchange-or-readonly: Pair `checked` with `onChange={…}` (controlled) or `readOnly` (display-only), and never combine `checked` with `defaultChecked`.
react-doctor/class-component-missing-component-will-unmount-teardown: Class component acquires a resource with no teardown

react-doctor/zustand-no-mutating-state