react/packages/react-dom/src/__tests__/ReactFunctionComponent-test.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.
 *
 * @emails react-core
 */

'use strict';

let PropTypes;
let React;
let ReactDOMClient;
let act;

function FunctionComponent(props) {
  return <div>{props.name}</div>;
}

describe('ReactFunctionComponent', () => {
  beforeEach(() => {
    jest.resetModules();
    PropTypes = require('prop-types');
    React = require('react');
    ReactDOMClient = require('react-dom/client');
    act = require('internal-test-utils').act;
  });

  it('should render stateless component', async () => {
    const el = document.createElement('div');

    const root = ReactDOMClient.createRoot(el);
    await act(() => {
      root.render(<FunctionComponent name="A" />);
    });

    expect(el.textContent).toBe('A');
  });

  it('should update stateless component', async () => {
    class Parent extends React.Component {
      render() {
        return <FunctionComponent {...this.props} />;
      }
    }

    const el = document.createElement('div');

    const root = ReactDOMClient.createRoot(el);
    await act(() => {
      root.render(<Parent name="A" />);
    });
    expect(el.textContent).toBe('A');

    await act(() => {
      root.render(<Parent name="B" />);
    });
    expect(el.textContent).toBe('B');
  });

  it('should unmount stateless component', async () => {
    const container = document.createElement('div');

    const root = ReactDOMClient.createRoot(container);
    await act(() => {
      root.render(<FunctionComponent name="A" />);
    });
    expect(container.textContent).toBe('A');

    root.unmount();
    expect(container.textContent).toBe('');
  });

  // @gate !disableLegacyContext
  it('should pass context thru stateless component', async () => {
    class Child extends React.Component {
      static contextTypes = {
        test: PropTypes.string.isRequired,
      };

      render() {
        return <div>{this.context.test}</div>;
      }
    }

    function Parent() {
      return <Child />;
    }

    class GrandParent extends React.Component {
      static childContextTypes = {
        test: PropTypes.string.isRequired,
      };

      getChildContext() {
        return {test: this.props.test};
      }

      render() {
        return <Parent />;
      }
    }

    const el = document.createElement('div');

    const root = ReactDOMClient.createRoot(el);
    await act(() => {
      root.render(<GrandParent test="test" />);
    });

    expect(el.textContent).toBe('test');

    await act(() => {
      root.render(<GrandParent test="mest" />);
    });

    expect(el.textContent).toBe('mest');
  });

  it('should warn for getDerivedStateFromProps on a function component', async () => {
    function FunctionComponentWithChildContext() {
      return null;
    }
    FunctionComponentWithChildContext.getDerivedStateFromProps = function () {};

    const container = document.createElement('div');

    await expect(async () => {
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<FunctionComponentWithChildContext />);
      });
    }).toErrorDev(
      'FunctionComponentWithChildContext: Function ' +
        'components do not support getDerivedStateFromProps.',
    );
  });

  it('should warn for childContextTypes on a function component', async () => {
    function FunctionComponentWithChildContext(props) {
      return <div>{props.name}</div>;
    }

    FunctionComponentWithChildContext.childContextTypes = {
      foo: PropTypes.string,
    };

    const container = document.createElement('div');

    await expect(async () => {
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<FunctionComponentWithChildContext name="A" />);
      });
    }).toErrorDev(
      'childContextTypes cannot ' + 'be defined on a function component.',
    );
  });

  it('should not throw when stateless component returns undefined', async () => {
    function NotAComponent() {}
    const container = document.createElement('div');
    const root = ReactDOMClient.createRoot(container);
    await expect(
      act(() => {
        root.render(
          <div>
            <NotAComponent />
          </div>,
        );
      }),
    ).resolves.not.toThrowError();
  });

  it('should throw on string refs in pure functions', async () => {
    function Child() {
      return <div ref="me" />;
    }

    const container = document.createElement('div');
    const root = ReactDOMClient.createRoot(container);
    await expect(
      act(() => {
        root.render(<Child test="test" />);
      }),
    ).rejects.toThrowError(
      __DEV__
        ? 'Function components cannot have string refs. We recommend using useRef() instead.'
        : // It happens because we don't save _owner in production for
          // function components.
          'Element ref was specified as a string (me) but no owner was set. This could happen for one of' +
            ' the following reasons:\n' +
            '1. You may be adding a ref to a function component\n' +
            "2. You may be adding a ref to a component that was not created inside a component's render method\n" +
            '3. You have multiple copies of React loaded\n' +
            'See https://reactjs.org/link/refs-must-have-owner for more information.',
    );
  });

  // @gate !enableRefAsProp || !__DEV__
  it('should warn when given a string ref', async () => {
    function Indirection(props) {
      return <div>{props.children}</div>;
    }

    class ParentUsingStringRef extends React.Component {
      render() {
        return (
          <Indirection>
            <FunctionComponent name="A" ref="stateless" />
          </Indirection>
        );
      }
    }

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<ParentUsingStringRef />);
      });
    }).toErrorDev(
      'Warning: Function components cannot be given refs. ' +
        'Attempts to access this ref will fail. ' +
        'Did you mean to use React.forwardRef()?\n\n' +
        'Check the render method ' +
        'of `ParentUsingStringRef`.\n' +
        '    in FunctionComponent (at **)\n' +
        '    in div (at **)\n' +
        '    in Indirection (at **)\n' +
        '    in ParentUsingStringRef (at **)',
    );

    // No additional warnings should be logged
    const container = document.createElement('div');
    const root = ReactDOMClient.createRoot(container);
    await act(() => {
      root.render(<ParentUsingStringRef />);
    });
  });

  // @gate !enableRefAsProp || !__DEV__
  it('should warn when given a function ref', async () => {
    function Indirection(props) {
      return <div>{props.children}</div>;
    }

    const ref = jest.fn();
    class ParentUsingFunctionRef extends React.Component {
      render() {
        return (
          <Indirection>
            <FunctionComponent name="A" ref={ref} />
          </Indirection>
        );
      }
    }

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<ParentUsingFunctionRef />);
      });
    }).toErrorDev(
      'Warning: Function components cannot be given refs. ' +
        'Attempts to access this ref will fail. ' +
        'Did you mean to use React.forwardRef()?\n\n' +
        'Check the render method ' +
        'of `ParentUsingFunctionRef`.\n' +
        '    in FunctionComponent (at **)\n' +
        '    in div (at **)\n' +
        '    in Indirection (at **)\n' +
        '    in ParentUsingFunctionRef (at **)',
    );
    expect(ref).not.toHaveBeenCalled();

    // No additional warnings should be logged
    const container = document.createElement('div');
    const root = ReactDOMClient.createRoot(container);
    await act(() => {
      root.render(<ParentUsingFunctionRef />);
    });
  });

  // @gate !enableRefAsProp || !__DEV__
  it('deduplicates ref warnings based on element or owner', async () => {
    // When owner uses JSX, we can use exact line location to dedupe warnings
    class AnonymousParentUsingJSX extends React.Component {
      render() {
        return <FunctionComponent name="A" ref={() => {}} />;
      }
    }

    let instance1;

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);

      await act(() => {
        root.render(
          <AnonymousParentUsingJSX ref={current => (instance1 = current)} />,
        );
      });
    }).toErrorDev('Warning: Function components cannot be given refs.');
    // Should be deduped (offending element is on the same line):
    instance1.forceUpdate();
    // Should also be deduped (offending element is on the same line):
    let container = document.createElement('div');
    let root = ReactDOMClient.createRoot(container);
    await act(() => {
      root.render(<AnonymousParentUsingJSX />);
    });

    // When owner doesn't use JSX, and is anonymous, we warn once per internal instance.
    class AnonymousParentNotUsingJSX extends React.Component {
      render() {
        return React.createElement(FunctionComponent, {
          name: 'A',
          ref: () => {},
        });
      }
    }

    let instance2;
    await expect(async () => {
      container = document.createElement('div');
      root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(
          <AnonymousParentNotUsingJSX ref={current => (instance2 = current)} />,
        );
      });
    }).toErrorDev('Warning: Function components cannot be given refs.');
    // Should be deduped (same internal instance, no additional warnings)
    instance2.forceUpdate();
    // Could not be differentiated (since owner is anonymous and no source location)
    container = document.createElement('div');
    root = ReactDOMClient.createRoot(container);
    await act(() => {
      root.render(<AnonymousParentNotUsingJSX />);
    });

    // When owner doesn't use JSX, but is named, we warn once per owner name
    class NamedParentNotUsingJSX extends React.Component {
      render() {
        return React.createElement(FunctionComponent, {
          name: 'A',
          ref: () => {},
        });
      }
    }
    let instance3;
    await expect(async () => {
      container = document.createElement('div');
      root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(
          <NamedParentNotUsingJSX ref={current => (instance3 = current)} />,
        );
      });
    }).toErrorDev('Warning: Function components cannot be given refs.');
    // Should be deduped (same owner name, no additional warnings):
    instance3.forceUpdate();
    // Should also be deduped (same owner name, no additional warnings):
    container = document.createElement('div');
    root = ReactDOMClient.createRoot(container);
    await act(() => {
      root.render(<NamedParentNotUsingJSX />);
    });
  });

  // This guards against a regression caused by clearing the current debug fiber.
  // https://github.com/facebook/react/issues/10831
  // @gate !disableLegacyContext || !__DEV__
  // @gate !enableRefAsProp || !__DEV__
  it('should warn when giving a function ref with context', async () => {
    function Child() {
      return null;
    }
    Child.contextTypes = {
      foo: PropTypes.string,
    };

    class Parent extends React.Component {
      static childContextTypes = {
        foo: PropTypes.string,
      };
      getChildContext() {
        return {
          foo: 'bar',
        };
      }
      render() {
        return <Child ref={function () {}} />;
      }
    }

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<Parent />);
      });
    }).toErrorDev(
      'Warning: Function components cannot be given refs. ' +
        'Attempts to access this ref will fail. ' +
        'Did you mean to use React.forwardRef()?\n\n' +
        'Check the render method ' +
        'of `Parent`.\n' +
        '    in Child (at **)\n' +
        '    in Parent (at **)',
    );
  });

  it('should use correct name in key warning', async () => {
    function Child() {
      return <div>{[<span />]}</div>;
    }

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<Child />);
      });
    }).toErrorDev(
      'Each child in a list should have a unique "key" prop.\n\n' +
        'Check the render method of `Child`.',
    );
  });

  it('should support default props', async () => {
    function Child(props) {
      return <div>{props.test}</div>;
    }
    Child.defaultProps = {test: 2};

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);

      await act(() => {
        root.render(<Child />);
      });
    }).toErrorDev([
      'Warning: Child: Support for defaultProps will be removed from function components in a future major release. Use JavaScript default parameters instead.',
    ]);
  });

  // @gate !disableLegacyContext
  it('should receive context', async () => {
    class Parent extends React.Component {
      static childContextTypes = {
        lang: PropTypes.string,
      };

      getChildContext() {
        return {lang: 'en'};
      }

      render() {
        return <Child />;
      }
    }

    function Child(props, context) {
      return <div>{context.lang}</div>;
    }
    Child.contextTypes = {lang: PropTypes.string};

    const el = document.createElement('div');

    const root = ReactDOMClient.createRoot(el);
    await act(() => {
      root.render(<Parent />);
    });
    expect(el.textContent).toBe('en');
  });

  it('should work with arrow functions', async () => {
    let Child = function () {
      return <div />;
    };
    // Will create a new bound function without a prototype, much like a native
    // arrow function.
    Child = Child.bind(this);

    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<Child />);
      });
    }).not.toThrow();
  });

  it('should allow simple functions to return null', async () => {
    const Child = function () {
      return null;
    };
    await expect(async () => {
      const container = document.createElement('div');
      const root = ReactDOMClient.createRoot(container);
      await act(() => {
        root.render(<Child />);
      });
    }).not.toThrow();
  });

  it('should allow simple functions to return false', async () => {
    function Child() {
      return false;
    }
    const container = document.createElement('div');
    const root = ReactDOMClient.createRoot(container);
    await expect(
      act(() => {
        root.render(<Child />);
      }),
    ).resolves.not.toThrow();
  });
});