Uncaught Error: Your custom UI reducer at path X must return some state

[economysizegeek]

I have two components that are nested Issues -> IssueCard. They each have their own customer reducers defined. When I unmount them - I get this error on the IssueCard path for the custom reducer.

The problem seems to be in action-reducer.js line ~144
var newState = func(mut.getIn(path), action);
if (newState === undefined) {
throw new Error('Your custom UI reducer at path ' + path.join('.') + ' must return some state');
}

The parent Issues gets unmounted this seems to wipe out the UI state for the child. Then it runs a second UI_UMOUNT_UI_STATE - it tries to run the custom reducer on a IssueCard (The state is undefined) and it returns undefined so the error trips.

This seems corrected by confirming that the existing state isn't already undefined before complaining:
if (newState === undefined && mut.getIn(path) !== undefined) {
throw new Error('Your custom UI reducer at path ' + path.join('.') + ' must return some state');
}

[tpinne]

I'm having the same problem. But in my case the nested component doesn't get unmounted. It only runs one @@redux-ui/UPDATE_UI_STATE action setting one value and then the console prints the error message.
As long as I can trust the redux dev tools in this case.