Restore API does not retain ROOT_QUERY, ROOT_MUTATION

Intended outcome:

Calling cache.gc() after the cache is restored using a tool like https://github.com/apollographql/apollo-cache-persist should not remove all entities in the cache and only remove unreachable entities.

Actual outcome:

Calling cache.gc() after the cache is restored using a tool like https://github.com/apollographql/apollo-cache-persist removes all entities in the cache.

Explanation

It looks like this happens because when you call cache.restore(data) as defined here: https://github.com/apollographql/apollo-client/blob/master/src/cache/inmemory/inMemoryCache.ts#L99

and subsequently call EntityStore replace: https://github.com/apollographql/apollo-client/blob/master/src/cache/inmemory/entityStore.ts#L238

it hydrates the cache, but never calls retain on any ID. Normally, the ROOT_QUERY is retained by a write to the store: https://github.com/apollographql/apollo-client/blob/master/src/cache/inmemory/writeToStore.ts#L114:L114

but if nothing has been written to the store yet, and gc is called immediately after a cache.restore using a tool like cache-persist, then there are no rootIds retained and the entire cache will get garbage collected.

I think the solution would be to either:

1. Default the rootIds to include ROOT_QUERY and ROOT_MUTATION on cache instantiation so that they are not lazily retained on a call to writeToStore but assumed to be desired to be retained by default
2. Retain ROOT_QUERY and ROOT_MUTATION if a call to cache.restore includes those keys at the time restore is called
3. Have downstream tools like cache-persist know that after doing a restore, they will need to retain IDs they care about like ROOT_QUERY and ROOT_MUTATION. I think this is a riskier approach, because as a user I would assume that ROOT_QUERY should be retained by default based on the documentation of cache.gc():

I think rootIds is not a familiar term to most folks in these docs and they’d assume that unreachable would mean that there are things like dangling normalized entities, not potentially the ROOT_QUERY itself.

Let me know what your thoughts are, thanks!

[loteoo]

@benjamn Genius, I was indeed importing getDataFromTree from @apollo/react-ssr. I switched the import to @apollo/client/react/ssr and it’s working properly with newer versions (now 3.3.6)

Thanks so much and sorry for the distraction!

[benjamn]

@loteoo If you’re not calling cache.gc() in that code, this issue (#7323) probably isn’t the cause of your problems, but getting an empty object is definitely strange/worrisome!

A couple more questions:

1. Are you importing getDataFromTree from @apollo/client/react/ssr?
2. Are you importing ApolloProvider from @apollo/client (or @apollo/client/react/context)?

The older @apollo/react-* packages should no longer be used.