codemod-replace-react-fc-typescript

A codemod using jscodeshift to remove React.FC and React.SFC from your codebase

(It's recommended to run your favorite formatting tool after the codemod 😉 )

👨‍🏫 Motivation

IF you use React and Typescript, you might have come across this GitHub PR in Create React App's repo about removing React.FC from their base template of a Typescript project.

The three main points that made me buy this was the fact that:

There's an implicit definition of children - all your components will have children typed!
They don't support generics
It does not correctly work with defaultProps

as well as other downsides (check out the PR description for that)

Motivated by that PR, and a lot of blog posts who also shared similar conclusions (and this ADR from Spotify's team in which they recorded the decision of removing React.FC from they codebase too), I wrote this little codemod that drops React.FC, React.FunctionComponent and React.SFC (which was also deprecated) and replaces the Props as the type of the unique argument in the component definition.

Let's see it with code

// before codemod runs
type Props2 = { id: number };
export const MyComponent2: React.FC<Props2> = (props) => {
  return <span>{props.id}</span>
}

// after codemod runs
type Props2 = { id: number };
export const MyComponent2 = (props: Props2) => {
  return <span>{props.id}</span>
}

It also works if the Props are defined inline

// before codemod runs
export const MyComponent4: React.FC<{ inlineProp: number, disabled?: boolean }> = (props) => <span>foo</span>

// after codemod runs
export const MyComponent4 = (
  props: {
    inlineProp: number,
    disabled?: boolean
  }
) => <span>foo</span>

It works with generics too!

// before codemod runs
type GenericsProps<T extends any> = { config: T }
export const MyComponentWithGenerics: React.FC<GenericsProps<string>> = (props) => <span>{props.config}</span>
export const MyComponentWithGenerics2: React.FC<GenericsProps<{ text: string }>> = ({ config: { text }}) => <span>{text}</span>

// after codemod runs
type GenericsProps<T extends any> = { config: T }
export const MyComponentWithGenerics = (props: GenericsProps<string>) => <span>{props.config}</span>
export const MyComponentWithGenerics2 = (
  {
    config: { text }
  }: GenericsProps<{ text: string }>
) => <span>{text}</span>

and with props defined with intersection

// before codemod runs
const WithIntersection: React.FC<Props1 & Props2> = ({ id, ...restProps }) => <span>{id}</span>

// after codemod runs
const WithIntersection = ( { id, ...restProps }: Props1 & Props2 ) => <span>{id}</span>

and with component modules defined using intersection

// before codemod runs
import React from 'react';
import { OtherComponent } from "./other-component";

interface Props { text: string }
const WithComponentIntersection: React.FC<Props> & {
  OtherComponent: typeof OtherComponent;
} = (props) => {
  return <span>{props.text}</span>
}
WithComponentIntersection.OtherComponent = OtherComponent;

// after codemod runs
import React from 'react';
import { OtherComponent } from "./other-component";

interface Props { text: string }
const WithComponentIntersection = (props: Props) => {
  return <span>{props.text}</span>
}
WithComponentIntersection.OtherComponent = OtherComponent;

Even with no Props!

// before codemod runs
const NoPropsComponent: React.FC = () => <span>foo</span>

// after codemod runs
const NoPropsComponent = () => <span>foo</span>

You don't have to stick with arrow functions only; all the previous scenarios work with regular named functions as well

// before codemod runs
import React from 'react'

interface Props { text: string }
const HelloWorld: React.SFC<Props> = function HelloWorld(props) {
  return <div>Hi {props.someValue}</div>
}

// after codemod runs
import React from 'react'

interface Props { text: string }
const HelloWorld = function HelloWorld(props: Props) {
  return <div>Hi {props.someValue}</div>
}

It also works when you use a function that accepts a component definition

// before codemod runs
import React from 'react';
import { observer } from "mobx-react-lite";

type Props = { id: number };
const functionAcceptsComponent: React.FC<Props> = observer((props) => {
  return <span>{props.id}</span>
})

// after codemod runs
import React from 'react';
import { observer } from "mobx-react-lite";

type Props = { id: number };
export const functionAcceptsComponent = observer((props: Props) => {
  return <span>{props.id}</span>
})

This codemod also works when using FC, FunctionComponent and SFC as a named export

// before codemod runs
import React, { FC } from 'react'

const NamedExportComponent: FC<Props> = (props) => <span>foo</span>

// after codemod runs
import React, { FC } from 'react'

const NamedExportComponent = (props: Props) => <span>foo</span>

🧰 How to use

1- Install jscodeshift

npm install -g jscodeshift

2- Run the following command

jscodeshift -t https://raw.githubusercontent.com/gndelia/codemod-replace-react-fc-typescript/main/dist/index.js --extensions=tsx --verbose=2 <FOLDER-YOU-WANT-TO-TRANSFORM>

There are other options you can read in the jscodeshift's Readme.

jscodeshift only accepts local transform files, or remote self-contained files. That's why I compiled the transform file into one distributable file using @vercel/ncc. If you don't want to run this remote file (because you might not trust, although you can read the source - it is totally safe), you can download this repo and run

jscodeshift -t Path/To/Repo/transform.ts --extensions=tsx --verbose=2 <FOLDER-YOU-WANT-TO-TRANSFORM>

📓 Notes

The codemod focuses in replacing the nodes but does not do styling. You might want to run Prettier or your favorite formatting tool after the code has been modified. For example, in the following code

import React from 'react'

interface Props { id: number, text: string }
const Component: React.FC<Props> = (props) => (
  <div>
    <span>{props.id}</span>
  </div>
)

after running the codemod, you might lose the parenthesis

import React from 'react'

interface Props { id: number, text: string }
const Component = (props: Props) => <div>
  <span>{props.id}</span>
</div>

this is because those parenthesis are not strictly required for the code to work. You can fix this by running Prettier (or whatever tool you're using to format your code) easily, as the code is still valid

If your component was using the implicit definition of children provided by React.FC, you will have to add the explicit definition or the code won't compile. For example, the following code

import React from 'react'

type Props = { title: string }
const Component: React.FC<Props> = ({ title, children }) => <div title={title}>{children}</div>

will be transformed into this after running the codemod

import React from 'react'

type Props = { title: string }
const Component = ({ title, children }: Props) => <div title={title}>{children}</div>

However, it won't compile because children is not part of your Props definition anymore. You can solve this by manually adding the type of children again.

The value that React.FC provides (that accepts anything you would accept in js as children) is { children?: ReactNode }. I'm intentionally not automatically adding it because you can restrict it to what you only want to accept (for instance, just a string, a number, only one component, and so on), and you know better than I do what you need.