Handling errors with ErrorPolicy all in Observable subscriptions?

[KeithGillette]

How do the various ApolloClient ErrorPolicy options interact with Apollo Angular's use of RxJS Observable subscriptions? I know that default none strips any returned data and calls the error subscription handler when an error is returned. But what happens with an error under ErrorPolicy all and none? The Apollo Angular documentation indicates it should be possible to render partial results since the response data is not discarded with ErrorPolicy all, but wouldn't that require calling both the next and error handlers, a seeming violation of the Observable contract?

[KeithGillette]

In testing, I found that setting errorPolicy: 'all' results in only the next and complete but never the error handler of the Observable subscription being called (and likewise, never the catchError operator in an Observable pipe). So that leads me to conclude that the next handler in the subscription would need to include any error-handling logic after explicitly testing for length in the errors array property of its FetchResult parameter. Alternatively, I suppose one could perform that errors array test in a map or other RxJS operator in a pipe from the Observable subscription, and then decide whether to return partial data or the error using the RxJS throwError operator.