Cache Read Failure in List with Nullable Items When Null Present

[mlarandeau]

Summary

We have various fields in our schema whose types are a nullable List containing nullable items (someField: [SomeType]) where the item type is a Union of a handful of other types. When parsing the live response there are no problems. However, when reading from the local cache, the read fails with JSONDecodingError.wrongType when one of the items within the list is null.

Version

1.15.2

Steps to reproduce the behavior

Setting some breakpoints within the Apollo SDK, I found that the error was being thrown from here. When inspecting the types, value was a CacheReference which that guard is trying to cast to a Record. Interestingly, when comparing the success and failure situations, I found that on success, when the list itself reaches that same line and is subsequently passed to executeChildSelections, the records for the items within the list are retrieved from the cache before circling back to the GraphQLExecuter. However, in the failure case, the item records never appear to be queried from the cache which presumably is how the CacheReferences end up getting passed back to the GraphQLExecutor.

I have only looked at this within the context of the memory cache and the data appears to write to the cache successfully.

So far we have verified this with two different fields/types in our schema but have heard additional reports that the "cache is not working".

Logs

Anything else?

Is there anything on our end that we should verify that we have configured properly?

[BobaFetters]

Thanks for the report, we will take a look into this

[mlarandeau]

Any updates on this? We are trying to decide how to move forward on our end and mostly curious at this point whether or not you agree that this seems to be an issue with the SDK that would require an update or if there is something on our end we should be doing differently. We are working on something that relies on caching and would prefer not to introduce our own caching layer in the interim.

[BobaFetters]

@mlarandeau sorry for the delayed response, it seems like this may be a bug on our end. Wondering if you would be able to provide a unit test or sample project that reproduces the issue to make this easier to track down, fix, and verify?