noComponentHookFactories (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.4.12
Diagnostic Category: lint/nursery/noComponentHookFactories
This rule doesn’t have a fix.
The default severity of this rule is error.
This rule belongs to the following domains:
- react
Sources:
- Same as react-hooks/component-hook-factories
- Same as react-x/component-hook-factories
- Same as @eslint-react/component-hook-factories

How to configure

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{
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  "linter": {
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    "rules": {
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      "nursery": {
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        "noComponentHookFactories": "error"
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      }
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    }
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  }
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}

Description

Disallows defining React components or custom hooks inside other functions.

Defining components or hooks inside other functions creates new instances on every call. React treats each new instance as a completely different component, which destroys and recreates the entire component subtree on each render and causes all state to be lost.

Examples

Invalid

A component is defined inside a factory function:

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function makeComponent(label) {
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  function MyComponent() {
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    return <div>{label}</div>;
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  }
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  return MyComponent;
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}

code-block.jsx:2:12 lint/nursery/noComponentHookFactories ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Do not define component MyComponent inside a function.
  
    1 │ function makeComponent(label) {
  > 2 │   function MyComponent() {
      │            ^^^^^^^^^^^
    3 │     return <div>{label}</div>;
    4 │   }
  
  ℹ React treats components defined inside functions as completely different on each call, destroying the entire subtree and losing all state. Move it to the module level.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

A hook is defined inside a factory function:

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function makeHook(key) {
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  function useMyHook() {
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    return useState(key);
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  }
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  return useMyHook;
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}

code-block.jsx:2:12 lint/nursery/noComponentHookFactories ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Do not define hook useMyHook inside a function.
  
    1 │ function makeHook(key) {
  > 2 │   function useMyHook() {
      │            ^^^^^^^^^
    3 │     return useState(key);
    4 │   }
  
  ℹ Each call creates a new hook identity, causing React to lose its state across renders. Move it to the module level.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

Valid

Components and hooks defined at the module level:

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function MyComponent() {
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  return <div>Hello</div>;
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}
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function useMyHook() {
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  return useState(0);
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}

Higher-order components that receive a component as a parameter are allowed:

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function withAuth(WrappedComponent) {
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  function AuthenticatedComponent(props) {
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    return <WrappedComponent {...props} />;
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  }
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  return AuthenticatedComponent;
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}