@apollo/client@4.3.0-alpha.3

Minor Changes

• #13324 0abd8de Thanks @jerelmiller! - Fix the accuracy of dataState in complex incremental streaming scenarios, especially when combined with returnPartialData: true.

  Prior to this change, all intermediate chunks used for both @defer and @stream directives returned a dataState of streaming, regardless of whether the actual data shape fit the definition of the streaming data state. The streaming data state represents an incomplete incremental response where the only holes in the data occur at @defer boundaries.

  Let's use the following example of where the previous dataState fell down when combined with returnPartialData.

  query GreetingQuery {
    greeting {
      message
      ... @defer {
        recipient {
          name
          email
        }
      }
    }
  }

  1. Scenario 1: partial data inside a @defer boundary written to the cache

  Let's say the cache contained the following partial data:

  {
    greeting: {
      __typename: "Greeting",
      recipient: {
        __typename: "Person",
        name: "John Doe",
      },
    },
  };

  After the first chunk arrives from the server, the data looks like the following:

  {
    greeting: {
      __typename: "Greeting",
      message: "Hello, John",
      recipient: {
        __typename: "Person",
        name: "John Doe",
      },
    },
  };

  This data is not complete because recipient.email is missing. This data is also not streaming because the data requirements in the @defer boundary are partially fulfilled due to the existence of recipient. This could lead to runtime crashes on recipient.email if you use the existence of recipient to detect whether data in the @defer boundary has streamed in or not. This change now accurately reports this as partial to ensure the field is marked as a partial field in recipient.

  2. Scenario 2: partial data written to the cache that fulfills the data requirements of the @defer boundary

  Let's say the cache contained the following partial data:

  {
    greeting: {
      __typename: "Greeting",
      recipient: {
        __typename: "Person",
        name: "John Doe",
        email: "john@example.com",
      },
    },
  };

  After the first chunk arrives from the server, the data looks like the following:

  {
    greeting: {
      __typename: "Greeting",
      message: "Hello, John",
      recipient: {
        __typename: "Person",
        name: "John Doe",
        email: "john@example.com",
      },
    },
  };

  In this case, the combination of the first chunk and the partial data in the cache now fulfills the data requirements of the query. Even though the server is still streaming data (NetworkStatus.streaming), we can report this as dataState: "complete" since it is safe to access data on all fields.

  This change also means @stream queries by definition fulfill the data requirements of the query after the first chunk arrives since @stream operates on lists and contains no data holes. @stream queries now accurately report dataState as complete or partial, depending on whether the list mixes partial data with streamed list items.

  As a result of this change, some cases where you'd previously see dataState reported as "streaming" are now reported as partial or complete.

  If you use dataState to determine whether an incremental request is still in-flight, please use networkStatus instead to check for NetworkStatus.streaming. dataState is type narrowing feature and not intended to report the network status.

Patch Changes

• #13324 0abd8de Thanks @jerelmiller! - Fix an issue where field read functions were not applied to intermediate results while streaming @defer responses. cache.diff ran the read functions, but the transformed values were only applied to the emitted result when the updated cache result was considered complete. Intermediate chunks whose only holes were at @defer boundaries now correctly return the result of field read functions.

  new InMemoryCache({
    typePolicies: {
      Greeting: {
        fields: {
          message: {
            read: (message) => message.toUpperCase(),
          },
        },
      },
    },
  });
  
  // query GreetingQuery {
  //   greeting {
  //     message
  //     ... @defer {
  //       recipient { name }
  //     }
  //   }
  // }
  
  // First chunk previously returned:
  // { greeting: { message: "Hello world" } }
  //
  // Now correctly returns while still streaming:
  // { greeting: { message: "HELLO WORLD" } }

• #13324 0abd8de Thanks @jerelmiller! - Fix an issue with @stream queries when using returnPartialData: true where the streamed list was truncated after the first incremental chunk when the list contained partial cache data. The list is no longer truncated and partial list items are now retained as incremental chunks arrive. The dataState is now reported as partial until the server has streamed enough of the list so that each list item fully satisfies the query.

  This change also updates @stream queries so that they reported with dataState: "complete instead of "streaming" since it is safe to access all fields in the response.