reactjs / reactjs/react.dev

[Suggestion]: Document that hooks can be called after a conditional `throw`

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type: documentation
Lenguaje dominante
JavaScript
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Descripción

Summary

I don't believe it is documented anywhere that calling a hook after a conditional throw statement is not a violation of the rules of hooks. If this is a valid pattern, it should be documented. If it is not, the Eslint rule rules-of-hooks should warn for it.

Page

Rules of hooks

Details

I realised this is effectively the pattern when using Next.js app router notFound(), which throws an Error in the component render. I had assumed this not being flagged by the rules-of-hooks was a limitation of the Next.js eslint plugin, but actually, this is not flagged as an issue with a standard throw:

const Component = ({ someOtherCondition }) => {
  const [foo, setFoo] = useState();

  if (someOtherCondition) throw new Error();

  const [bar, setBar] = useState();

  return (<>...</>);
};

My assumption is this is a valid pattern as if someOtherCondition becomes true, the error will be thrown up the call stack to the nearest error boundary, and the render that was in-progress will be discarded. There is not a case to have this conditional throw call more hooks than the previous render, only less. The rules of hooks state:

It’s not supported to call Hooks (functions starting with use) in any other cases, for example:

🔴 Do not call Hooks inside conditions or loops.
🔴 Do not call Hooks after a conditional return statement.

In the example above, the second useState call comes after a conditional throw statement. Not quite either of the cases in documentation.

If this is a valid pattern, it should be mentioned in the docs, with potential warnings about it not being a recommended workaround to conditionally call hooks (as there is no way to resume execution of the other path of the conditional once an error is thrown from the component).

If this isn't a valid pattern, it should be flagged by the eslint rule.

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Línea de trabajo

Comienza con la página «Rules of Hooks» y el comportamiento documentado de rules-of-hooks descrito en el issue. Reproduce el ejemplo de throw condicional y determina después si la página necesita una aclaración o si debería cambiar la regla de ESLint; el trabajo está terminado cuando el comportamiento y la orientación prevista para él estén resueltos y reflejados en el lugar adecuado.

Escrito por el modelo de indexación a partir del texto del issue.

Evaluación

Stack tecnológico
eslint, javascript, next.js, react
Área
documentation
Tipo de issue
Documentación
Dificultad
4/5
Tiempo estimado
3-5 días
Estado de actividad
Estancado
Claridad
Necesita aclaración
Aptitud para principiantes
35/100

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