React - Functional error boundaries

_readme.md

React - Functional error boundaries

Thanks to React hooks you have now happily turned all your classes into functional components.

Wait, all your components? Not quite. There is one thing that can still only be implemented using classes: Error boundaries.

There is just no functional equivalent for componentDidCatch and deriveStateFromError yet.

Proposed solution

The proposed solution is greatly inspired by the new React.memo() API.

import Catch from "./functional-error-boundary"

type Props = {
  children: React.ReactNode
}

const MyErrorBoundary = Catch(function MyErrorBoundary(props: Props, error?: Error) {
  if (error) {
    return (
      <div className="error-screen">
        <h2>An error has occured</h2>
        <h4>{error.message}</h4>
      </div>
    )
  } else {
    return <React.Fragment>{props.children}</React.Fragment>
  }
})

API

type ErrorHandler = (error: Error, info: React.ErrorInfo) => void

Catch(component: React.ComponentType)

Catch(component: React.ComponentType, errorHandler: ErrorHandler)

Wraps the functional component component to make it an error boundary. The caught error is passed to the component function as a second parameter.

The optional second argument to Catch() (errorHandler) is a function that acts as componentDidCatch(). Use it to handle side effects like error logging.

Implementation

Find the code below.

Outlook

Would be great to see something like this integrated into the React.js core library:

import React from "react"

type Props = {
  children: React.ReactNode
}

const MyErrorBoundary = React.Catch(function MyErrorBoundary(props: Props, error?: Error) {
  if (error) {
    return (
      <div className="error-screen">
        <h2>An error has occured</h2>
        <h4>{error.message}</h4>
      </div>
    )
  } else {
    return <React.Fragment>{props.children}</React.Fragment>
  }
})

functional-error-boundary.tsx

import React from "react"

type ErrorHandler = (error: Error, info: React.ErrorInfo) => void
type ErrorHandlingComponent<Props> = (props: Props, error?: Error) => React.ReactNode

type ErrorState = { error?: Error }

export default function Catch<Props extends {}>(
  component: ErrorHandlingComponent<Props>,
  errorHandler?: ErrorHandler
): React.ComponentType<Props> {
  return class extends React.Component<Props, ErrorState> {
    state: ErrorState = {
      error: undefined
    }
    
    static getDerivedStateFromError(error: Error) {
      return { error }
    }
    
    componentDidCatch(error: Error, info: React.ErrorInfo) {
      if (errorHandler) {
        errorHandler(error, info)
      }
    }
    
    render() {
      return component(this.props, this.state.error)
    }
  }
}