meteor/packages/react-fast-refresh/server.js

let enabled = !process.env.DISABLE_REACT_FAST_REFRESH;

if (enabled) {
  try {
    // React fast refresh requires react 16.9.0 or newer
    const semver = require('semver');
    const pkg = require('react/package.json');

    enabled = pkg && pkg.version &&
      semver.gte(pkg.version, '16.9.0');
  } catch (e) {
    // If the app doesn't directly depend on react, leave react-refresh
    // enabled in case a package or indirect dependency uses react.
  }
}

const babelPlugin = enabled ?
  require('react-refresh/babel') :
  null;

ReactFastRefresh = {
  babelPlugin,
};