react-native/packages/react-native/jest/mockComponent.js

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 */

'use strict';

module.exports = (moduleName, instanceMethods, isESModule) => {
  const RealComponent = isESModule
    ? jest.requireActual(moduleName).default
    : jest.requireActual(moduleName);
  const React = require('react');

  const SuperClass =
    typeof RealComponent === 'function' ? RealComponent : React.Component;

  const name =
    RealComponent.displayName ||
    RealComponent.name ||
    (RealComponent.render // handle React.forwardRef
      ? RealComponent.render.displayName || RealComponent.render.name
      : 'Unknown');

  const nameWithoutPrefix = name.replace(/^(RCT|RK)/, '');

  const Component = class extends SuperClass {
    static displayName = 'Component';

    render() {
      const props = Object.assign({}, RealComponent.defaultProps);

      if (this.props) {
        Object.keys(this.props).forEach(prop => {
          // We can't just assign props on top of defaultProps
          // because React treats undefined as special and different from null.
          // If a prop is specified but set to undefined it is ignored and the
          // default prop is used instead. If it is set to null, then the
          // null value overwrites the default value.
          if (this.props[prop] !== undefined) {
            props[prop] = this.props[prop];
          }
        });
      }

      return React.createElement(nameWithoutPrefix, props, this.props.children);
    }
  };

  Component.displayName = nameWithoutPrefix;

  Object.keys(RealComponent).forEach(classStatic => {
    Component[classStatic] = RealComponent[classStatic];
  });

  if (instanceMethods != null) {
    Object.assign(Component.prototype, instanceMethods);
  }

  return Component;
};