#12923 94ea3e3 Thanks @jerelmiller! - Fix an issue where deferred payloads that returned arrays with fewer items than the original cached array would retain items from the cached array. This change includes @stream arrays where stream arrays replace the cached arrays.

#12927 96b531f Thanks @jerelmiller! - Don't set the fallback value of a @client field to null when a read function is defined. Instead the read function will be called with an existing value of undefined to allow default arguments to be used to set the returned value.

When a read function is not defined nor is there a defined resolver for the field, warn and set the value to null only in that instance.

#12927 45ebb52 Thanks @jerelmiller! - Add support for from: null in client.watchFragment and cache.watchFragment. When from is null, the emitted result is:

{
  data: null,
  dataState: "complete",
  complete: true,
}

#12926 2b7f2c1 Thanks @jerelmiller! - Support the newer incremental delivery format for the @defer directive implemented in graphql@17.0.0-alpha.9. Import the GraphQL17Alpha9Handler to use the newer incremental delivery format with @defer.

import { GraphQL17Alpha9Handler } from "@apollo/client/incremental";

const client = new ApolloClient({
  // ...
  incrementalHandler: new GraphQL17Alpha9Handler(),
});

[!NOTE] In order to use the GraphQL17Alpha9Handler, the GraphQL server MUST implement the newer incremental delivery format. You may see errors or unusual behavior if you use the wrong handler. If you are using Apollo Router, continue to use the Defer20220824Handler because Apollo Router does not yet support the newer incremental delivery format.

#12927 45ebb52 Thanks @jerelmiller! - Add support for arrays with useFragment, useSuspenseFragment, and client.watchFragment. This allows the ability to use a fragment to watch multiple entities in the cache. Passing an array to from will return data as an array where each array index corresponds to the index in the from array.

function MyComponent() {
  const result = useFragment({
    fragment,
    from: [item1, item2, item3],
  });

  // `data` is an array with 3 items
  console.log(result); // { data: [{...}, {...}, {...}], dataState: "complete", complete: true }
}

#12927 45ebb52 Thanks @jerelmiller! - Add a getCurrentResult function to the observable returned by client.watchFragment and cache.watchFragment that returns the current value for the watched fragment.

const observable = client.watchFragment({
  fragment,
  from: { __typename: "Item", id: 1 },
});

console.log(observable.getCurrentResult());
// {
//   data: {...},
//   dataState: "complete",
//   complete: true,
// }

#13038 109efe7 Thanks @jerelmiller! - Add the from option to readFragment, watchFragment, and updateFragment.

#12918 2e224b9 Thanks @jerelmiller! - Add support for the @stream directive on both the Defer20220824Handler and the GraphQL17Alpha2Handler.

[!NOTE] The implementations of @stream differ in the delivery of incremental results between the different GraphQL spec versions. If you upgrading from the older format to the newer format, expect the timing of some incremental results to change.

#13056 b224efc Thanks @jerelmiller! - InMemoryCache no longer filters out explicitly returned undefined items from read functions for array fields. This now makes it possible to create read functions on array fields that return partial data and trigger a fetch for the full list.

#13058 121a2cb Thanks @jerelmiller! - Add an extensions option to cache.write, cache.writeQuery, and client.writeQuery. This makes extensions available in cache merge functions which can be accessed with the other merge function options.

As a result of this change, any extensions returned in GraphQL operations are now available in merge in the cache writes for these operations.

#12927 96b531f Thanks @jerelmiller! - Add an abstract resolvesClientField function to ApolloCache that can be used by caches to tell LocalState if it can resolve a @client field when a local resolver is not defined.

LocalState will emit a warning and set a fallback value of null when no local resolver is defined and resolvesClientField returns false, or isn't defined. Returning true from resolvesClientField signals that a mechanism in the cache will set the field value. In this case, LocalState won't set the field value.

#13078 bf1e0dc Thanks @phryneas! - Use the default stream merge function for @stream fields only if stream info is present. This change means that using the older Defer20220824Handler will not use the default stream merge function and will instead truncate the streamed array on the first chunk.