[DEPRECATED] React Compiler compatibility module for codebases unable to use React 19

babel.config.js

module.exports = function(api) {
  return {
    plugins: [
      [
        'babel-plugin-react-compiler', {
          runtimeModule: 'react-compiler-runtime'
        }
      ]
    ]
  }
}

package.json

{
  "dependencies": {
    "react-compiler-runtime": "file:./lib/react-compiler-runtime"
  },
  "devDependencies": {
    "babel-plugin-react-compiler": "latest"
  }
}

react-compiler-runtime-index.js

// lib/react-compiler-runtime/index.js

import React from 'react';

const $empty = Symbol.for("react.memo_cache_sentinel");
/**
 * DANGER: this hook is NEVER meant to be called directly!
 *
 * Note that this is a temporary userspace implementation of this function
 * from React 19. It is not as efficient and may invalidate more frequently
 * than the official API. Please upgrade to React 19 as soon as you can.
 **/
export function c(size) {
  return React.useState(() => {
    const $ = new Array(size);
    for (let ii = 0; ii < size; ii++) {
      $[ii] = $empty;
    }
    // @ts-ignore
    $[$empty] = true;
    return $;
  })[0];
}

react-compiler-runtime-package.json

// lib/react-compiler-runtime/package.json
{
  "name": "react-compiler-runtime",
  "version": "0.0.1",
  "license": "MIT",
  "main": "index.js",
  "dependencies": {
    "react": "^18.2.0"
  }
}

nit:

12 export function c(size: number) {

has a : number type annotation, which is not javascript

updated gist to esm and removed type annotations

Please note that you no longer need this gist, you can follow the docs on how to get the compiler to work with React <19.