Function isLikelyComponentType

packages/react-refresh/src/ReactFreshRuntime.js:659–710

(type: any)

}

export function isLikelyComponentType(type: any): boolean {
  if (__DEV__) {
    switch (typeof type) {
      case 'function': {
        // First, deal with classes.
        if (type.prototype != null) {
          if (type.prototype.isReactComponent) {
            // React class.
            return true;
          }
          const ownNames = Object.getOwnPropertyNames(type.prototype);
          if (ownNames.length > 1 || ownNames[0] !== 'constructor') {
            // This looks like a class.
            return false;
          }
          if (
            // $FlowFixMe[prop-missing]
            type.prototype.__proto__ !== Object.prototype // eslint-disable-line no-proto
          ) {
            // It has a superclass.
            return false;
          }
          // Pass through.
          // This looks like a regular function with empty prototype.
        }
        // For plain functions and arrows, use name as a heuristic.
        const name = type.name || type.displayName;
        return typeof name === 'string' && /^[A-Z]/.test(name);
      }
      case 'object': {
        if (type != null) {
          switch (getProperty(type, '$$typeof')) {
            case REACT_FORWARD_REF_TYPE:
            case REACT_MEMO_TYPE:
              // Definitely React components.
              return true;
            default:
              return false;
          }
        }
        return false;
      }
      default: {
        return false;
      }
    }
  } else {
    throw new Error(
      'Unexpected call to React Refresh in a production environment.',
    );
  }
}