Cannot ready property 'readContext' of undefined

[kevinwolfcr]

Do you want to request a feature or report a bug?
Report a bug

What is the current behavior?
react-cache is not working with Suspense.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Your bug will get fixed much faster if we can run your code and it doesn't have dependencies other than React. Paste the link to your JSFiddle (https://jsfiddle.net/Luktwrdm/) or CodeSandbox
https://codesandbox.io/s/3jw6y3ww6

What is the expected behavior?
To show the loading screen, or at least not to fail

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?
react: 16.8.0-alpha.0
react-dom: 16.8.0-alpha.0
react-cache: 2.0.0-alpha.1

[498628255]

If you just want to run the program in the development env, you can modify the code in 'react-cache/cjs/react-cache.development.js' by yourself:
old:

var currentOwner = React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED.ReactCurrentOwner;

function readContext(Context, observedBits) {
  var dispatcher = currentOwner.currentDispatcher;
  if (dispatcher === null) {
    throw new Error('react-cache: read and preload may only be called from within a ' + "component's render. They are not supported in event handlers or " + 'lifecycle methods.');
  }
  return dispatcher.readContext(Context, observedBits);
}

'currentOwner' is no use except in function readContext. so here is the new:

var currentDispatcher = React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED.ReactCurrentDispatcher;

function readContext(Context, observedBits) {
  var dispatcher = currentDispatcher.current;
  if (dispatcher === null) {
    throw new Error('react-cache: read and preload may only be called from within a ' + "component's render. They are not supported in event handlers or " + 'lifecycle methods.');
  }
  return dispatcher.readContext(Context, observedBits);
}

And that work in my code.

[threepointone]

Did you delete your codesandbox repro? Please add it so I can have a look. also, can you try with the newer alpha? (16.8.0-alpha.1)

[gaearon]

(This is expected to not work until we release an update to react-cache that uses the new dispatcher field)

[gaearon]

See #14780 (comment).