react/packages/react-dom/src/__tests__/ReactDOMRoot-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 React = require('react');
let ReactDOM = require('react-dom');
let ReactDOMClient = require('react-dom/client');
let ReactDOMServer = require('react-dom/server');
let Scheduler = require('scheduler');
let act;
let useEffect;

describe('ReactDOMRoot', () => {
  let container;

  beforeEach(() => {
    jest.resetModules();
    container = document.createElement('div');
    React = require('react');
    ReactDOM = require('react-dom');
    ReactDOMClient = require('react-dom/client');
    ReactDOMServer = require('react-dom/server');
    Scheduler = require('scheduler');
    act = require('jest-react').act;
    useEffect = React.useEffect;
  });

  it('renders children', () => {
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
  });

  it('warns if you import createRoot from react-dom', async () => {
    expect(() => ReactDOM.createRoot(container)).toErrorDev(
      'You are importing createRoot from "react-dom" which is not supported. ' +
        'You should instead import it from "react-dom/client".',
      {
        withoutStack: true,
      },
    );
  });

  it('warns if you import hydrateRoot from react-dom', async () => {
    expect(() => ReactDOM.hydrateRoot(container, null)).toErrorDev(
      'You are importing hydrateRoot from "react-dom" which is not supported. ' +
        'You should instead import it from "react-dom/client".',
      {
        withoutStack: true,
      },
    );
  });

  it('warns if a callback parameter is provided to render', () => {
    const callback = jest.fn();
    const root = ReactDOMClient.createRoot(container);
    expect(() => root.render(<div>Hi</div>, callback)).toErrorDev(
      'render(...): does not support the second callback argument. ' +
        'To execute a side effect after rendering, declare it in a component body with useEffect().',
      {withoutStack: true},
    );
    Scheduler.unstable_flushAll();
    expect(callback).not.toHaveBeenCalled();
  });

  it('warn if a container is passed to root.render(...)', async () => {
    function App() {
      return 'Child';
    }

    const root = ReactDOMClient.createRoot(container);
    expect(() => root.render(<App />, {})).toErrorDev(
      'You passed a second argument to root.render(...) but it only accepts ' +
        'one argument.',
      {
        withoutStack: true,
      },
    );
  });

  it('warn if a container is passed to root.render(...)', async () => {
    function App() {
      return 'Child';
    }

    const root = ReactDOMClient.createRoot(container);
    expect(() => root.render(<App />, container)).toErrorDev(
      'You passed a container to the second argument of root.render(...). ' +
        "You don't need to pass it again since you already passed it to create " +
        'the root.',
      {
        withoutStack: true,
      },
    );
  });

  it('warns if a callback parameter is provided to unmount', () => {
    const callback = jest.fn();
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    expect(() => root.unmount(callback)).toErrorDev(
      'unmount(...): does not support a callback argument. ' +
        'To execute a side effect after rendering, declare it in a component body with useEffect().',
      {withoutStack: true},
    );
    Scheduler.unstable_flushAll();
    expect(callback).not.toHaveBeenCalled();
  });

  it('unmounts children', () => {
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    root.unmount();
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('');
  });

  it('supports hydration', async () => {
    const markup = await new Promise(resolve =>
      resolve(
        ReactDOMServer.renderToString(
          <div>
            <span className="extra" />
          </div>,
        ),
      ),
    );

    // Does not hydrate by default
    const container1 = document.createElement('div');
    container1.innerHTML = markup;
    const root1 = ReactDOMClient.createRoot(container1);
    root1.render(
      <div>
        <span />
      </div>,
    );
    Scheduler.unstable_flushAll();

    const container2 = document.createElement('div');
    container2.innerHTML = markup;
    ReactDOMClient.hydrateRoot(
      container2,
      <div>
        <span />
      </div>,
    );
    expect(() => Scheduler.unstable_flushAll()).toErrorDev('Extra attributes');
  });

  it('clears existing children with legacy API', async () => {
    container.innerHTML = '<div>a</div><div>b</div>';
    ReactDOM.render(
      <div>
        <span>c</span>
        <span>d</span>
      </div>,
      container,
    );
    expect(container.textContent).toEqual('cd');
    ReactDOM.render(
      <div>
        <span>d</span>
        <span>c</span>
      </div>,
      container,
    );
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('dc');
  });

  it('clears existing children', async () => {
    container.innerHTML = '<div>a</div><div>b</div>';
    const root = ReactDOMClient.createRoot(container);
    root.render(
      <div>
        <span>c</span>
        <span>d</span>
      </div>,
    );
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('cd');
    root.render(
      <div>
        <span>d</span>
        <span>c</span>
      </div>,
    );
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('dc');
  });

  it('throws a good message on invalid containers', () => {
    expect(() => {
      ReactDOMClient.createRoot(<div>Hi</div>);
    }).toThrow('createRoot(...): Target container is not a DOM element.');
  });

  it('warns when rendering with legacy API into createRoot() container', () => {
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    expect(() => {
      ReactDOM.render(<div>Bye</div>, container);
    }).toErrorDev(
      [
        // We care about this warning:
        'You are calling ReactDOM.render() on a container that was previously ' +
          'passed to ReactDOMClient.createRoot(). This is not supported. ' +
          'Did you mean to call root.render(element)?',
        // This is more of a symptom but restructuring the code to avoid it isn't worth it:
        'Replacing React-rendered children with a new root component.',
      ],
      {withoutStack: true},
    );
    Scheduler.unstable_flushAll();
    // This works now but we could disallow it:
    expect(container.textContent).toEqual('Bye');
  });

  it('warns when hydrating with legacy API into createRoot() container', () => {
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    expect(() => {
      ReactDOM.hydrate(<div>Hi</div>, container);
    }).toErrorDev(
      [
        // We care about this warning:
        'You are calling ReactDOM.hydrate() on a container that was previously ' +
          'passed to ReactDOMClient.createRoot(). This is not supported. ' +
          'Did you mean to call hydrateRoot(container, element)?',
        // This is more of a symptom but restructuring the code to avoid it isn't worth it:
        'Replacing React-rendered children with a new root component.',
      ],
      {withoutStack: true},
    );
  });

  it('callback passed to legacy hydrate() API', () => {
    container.innerHTML = '<div>Hi</div>';
    ReactDOM.hydrate(<div>Hi</div>, container, () => {
      Scheduler.unstable_yieldValue('callback');
    });
    expect(container.textContent).toEqual('Hi');
    expect(Scheduler).toHaveYielded(['callback']);
  });

  it('warns when unmounting with legacy API (no previous content)', () => {
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    let unmounted = false;
    expect(() => {
      unmounted = ReactDOM.unmountComponentAtNode(container);
    }).toErrorDev(
      [
        // We care about this warning:
        'You are calling ReactDOM.unmountComponentAtNode() on a container that was previously ' +
          'passed to ReactDOMClient.createRoot(). This is not supported. Did you mean to call root.unmount()?',
        // This is more of a symptom but restructuring the code to avoid it isn't worth it:
        "The node you're attempting to unmount was rendered by React and is not a top-level container.",
      ],
      {withoutStack: true},
    );
    expect(unmounted).toBe(false);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    root.unmount();
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('');
  });

  it('warns when unmounting with legacy API (has previous content)', () => {
    // Currently createRoot().render() doesn't clear this.
    container.appendChild(document.createElement('div'));
    // The rest is the same as test above.
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    let unmounted = false;
    expect(() => {
      unmounted = ReactDOM.unmountComponentAtNode(container);
    }).toErrorDev(
      [
        'Did you mean to call root.unmount()?',
        // This is more of a symptom but restructuring the code to avoid it isn't worth it:
        "The node you're attempting to unmount was rendered by React and is not a top-level container.",
      ],
      {withoutStack: true},
    );
    expect(unmounted).toBe(false);
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('Hi');
    root.unmount();
    Scheduler.unstable_flushAll();
    expect(container.textContent).toEqual('');
  });

  it('warns when passing legacy container to createRoot()', () => {
    ReactDOM.render(<div>Hi</div>, container);
    expect(() => {
      ReactDOMClient.createRoot(container);
    }).toErrorDev(
      'You are calling ReactDOMClient.createRoot() on a container that was previously ' +
        'passed to ReactDOM.render(). This is not supported.',
      {withoutStack: true},
    );
  });

  it('warns when creating two roots managing the same container', () => {
    ReactDOMClient.createRoot(container);
    expect(() => {
      ReactDOMClient.createRoot(container);
    }).toErrorDev(
      'You are calling ReactDOMClient.createRoot() on a container that ' +
        'has already been passed to createRoot() before. Instead, call ' +
        'root.render() on the existing root instead if you want to update it.',
      {withoutStack: true},
    );
  });

  it('does not warn when creating second root after first one is unmounted', () => {
    const root = ReactDOMClient.createRoot(container);
    root.unmount();
    Scheduler.unstable_flushAll();
    ReactDOMClient.createRoot(container); // No warning
  });

  it('warns if creating a root on the document.body', async () => {
    if (gate(flags => flags.enableFloat)) {
      // we no longer expect an error for this if float is enabled
      ReactDOMClient.createRoot(document.body);
    } else {
      expect(() => {
        ReactDOMClient.createRoot(document.body);
      }).toErrorDev(
        'createRoot(): Creating roots directly with document.body is ' +
          'discouraged, since its children are often manipulated by third-party ' +
          'scripts and browser extensions. This may lead to subtle ' +
          'reconciliation issues. Try using a container element created ' +
          'for your app.',
        {withoutStack: true},
      );
    }
  });

  it('warns if updating a root that has had its contents removed', async () => {
    const root = ReactDOMClient.createRoot(container);
    root.render(<div>Hi</div>);
    Scheduler.unstable_flushAll();
    container.innerHTML = '';

    if (gate(flags => flags.enableFloat || flags.enableHostSingletons)) {
      // When either of these flags are on this validation is turned off so we
      // expect there to be no warnings
      root.render(<div>Hi</div>);
    } else {
      expect(() => {
        root.render(<div>Hi</div>);
      }).toErrorDev(
        'render(...): It looks like the React-rendered content of the ' +
          'root container was removed without using React. This is not ' +
          'supported and will cause errors. Instead, call ' +
          "root.unmount() to empty a root's container.",
        {withoutStack: true},
      );
    }
  });

  it('opts-in to concurrent default updates', async () => {
    const root = ReactDOMClient.createRoot(container, {
      unstable_concurrentUpdatesByDefault: true,
    });

    function Foo({value}) {
      Scheduler.unstable_yieldValue(value);
      return <div>{value}</div>;
    }

    await act(async () => {
      root.render(<Foo value="a" />);
    });

    expect(container.textContent).toEqual('a');

    await act(async () => {
      root.render(<Foo value="b" />);

      expect(Scheduler).toHaveYielded(['a']);
      expect(container.textContent).toEqual('a');

      expect(Scheduler).toFlushAndYieldThrough(['b']);
      if (gate(flags => flags.allowConcurrentByDefault)) {
        expect(container.textContent).toEqual('a');
      } else {
        expect(container.textContent).toEqual('b');
      }
    });
    expect(container.textContent).toEqual('b');
  });

  it('unmount is synchronous', async () => {
    const root = ReactDOMClient.createRoot(container);
    await act(async () => {
      root.render('Hi');
    });
    expect(container.textContent).toEqual('Hi');

    await act(async () => {
      root.unmount();
      // Should have already unmounted
      expect(container.textContent).toEqual('');
    });
  });

  it('throws if an unmounted root is updated', async () => {
    const root = ReactDOMClient.createRoot(container);
    await act(async () => {
      root.render('Hi');
    });
    expect(container.textContent).toEqual('Hi');

    root.unmount();

    expect(() => root.render("I'm back")).toThrow(
      'Cannot update an unmounted root.',
    );
  });

  it('warns if root is unmounted inside an effect', async () => {
    const container1 = document.createElement('div');
    const root1 = ReactDOMClient.createRoot(container1);
    const container2 = document.createElement('div');
    const root2 = ReactDOMClient.createRoot(container2);

    function App({step}) {
      useEffect(() => {
        if (step === 2) {
          root2.unmount();
        }
      }, [step]);
      return 'Hi';
    }

    await act(async () => {
      root1.render(<App step={1} />);
    });
    expect(container1.textContent).toEqual('Hi');

    expect(() => {
      ReactDOM.flushSync(() => {
        root1.render(<App step={2} />);
      });
    }).toErrorDev(
      'Attempted to synchronously unmount a root while React was ' +
        'already rendering.',
    );
  });

  // @gate disableCommentsAsDOMContainers
  it('errors if container is a comment node', () => {
    // This is an old feature used by www. Disabled in the open source build.
    const div = document.createElement('div');
    div.innerHTML = '<!-- react-mount-point-unstable -->';
    const commentNode = div.childNodes[0];

    expect(() => ReactDOMClient.createRoot(commentNode)).toThrow(
      'createRoot(...): Target container is not a DOM element.',
    );
    expect(() => ReactDOMClient.hydrateRoot(commentNode)).toThrow(
      'hydrateRoot(...): Target container is not a DOM element.',
    );

    // Still works in the legacy API
    ReactDOM.render(<div />, commentNode);
  });

  it('warn if no children passed to hydrateRoot', async () => {
    expect(() => ReactDOMClient.hydrateRoot(container)).toErrorDev(
      'Must provide initial children as second argument to hydrateRoot.',
      {withoutStack: true},
    );
  });

  it('warn if JSX passed to createRoot', async () => {
    function App() {
      return 'Child';
    }

    expect(() => ReactDOMClient.createRoot(container, <App />)).toErrorDev(
      'You passed a JSX element to createRoot. You probably meant to call ' +
        'root.render instead',
      {
        withoutStack: true,
      },
    );
  });
});