WarnIfLegacyBackendDetected() — react Function Reference

Source Code

packages/react-devtools-shared/src/devtools/views/WarnIfLegacyBackendDetected.js lines 17–76

export default function WarnIfLegacyBackendDetected(_: {}): null {
  const bridge = useContext(BridgeContext);
  const {dispatch} = useContext(ModalDialogContext);

  // Detect pairing with legacy v3 backend.
  // We do this by listening to a message that it broadcasts but the v4 backend doesn't.
  // In this case the frontend should show upgrade instructions.
  useEffect(() => {
    // Wall.listen returns a cleanup function
    let unlisten: $FlowFixMe = bridge.wall.listen(message => {
      switch (message.type) {
        case 'call':
        case 'event':
        case 'many-events':
          // Any of these types indicate the v3 backend.
          dispatch({
            canBeDismissed: false,
            id: 'WarnIfLegacyBackendDetected',
            type: 'SHOW',
            title: 'DevTools v4 is incompatible with this version of React',
            content: <InvalidBackendDetected />,
          });

          // Once we've identified the backend version, it's safe to unsubscribe.
          if (typeof unlisten === 'function') {
            unlisten();
            unlisten = null;
          }
          break;
        default:
          break;
      }

      switch (message.event) {
        case 'isBackendStorageAPISupported':
        case 'isNativeStyleEditorSupported':
        case 'operations':
        case 'overrideComponentFilters':
          // Any of these is sufficient to indicate a v4 backend.
          // Once we've identified the backend version, it's safe to unsubscribe.
          if (typeof unlisten === 'function') {
            unlisten();
            unlisten = null;
          }
          break;
        default:
          break;
      }
    });

    return () => {
      if (typeof unlisten === 'function') {
        unlisten();
        unlisten = null;
      }
    };
  }, [bridge, dispatch]);

  return null;
}