Connection and collection segment fields lose ParallelExecutable when global field middleware is registered #10563

Product

Hot Chocolate

Version

16.6.7

Link to minimal reproduction

https://github.com/bbarry/graphql-platform/blob/feature/pagination-fields-parallel/src/HotChocolate/Core/test/Types.CursorPagination.Tests/ConnectionTypeTests.cs

Steps to reproduce

1. git clone https://github.com/bbarry/graphql-platform.git && cd graphql-platform
2. git checkout feature/pagination-fields-parallel
3. Restore the unfixed types (the branch's last commit contains the fix):
   git checkout HEAD1 -- src/HotChocolate/Core/src/Types.CursorPagination/ConnectionType.cs "src/HotChocolate/Core/src/Types.OffsetPagination/CollectionSegmentType1.cs"
4. dotnet test src/HotChocolate/Core/test/Types.CursorPagination.Tests -f net11.0 -- --filter-method "ConnectionTypeTests"
   dotnet test src/HotChocolate/Core/test/Types.OffsetPagination.Tests -f net11.0 -- --filter-method "CollectionSegmentTypeTests"

test files:

• https://github.com/bbarry/graphql-platform/blob/feature/pagination-fields-parallel/src/HotChocolate/Core/test/Types.CursorPagination.Tests/ConnectionTypeTests.cs
• https://github.com/bbarry/graphql-platform/blob/feature/pagination-fields-parallel/src/HotChocolate/Core/test/Types.OffsetPagination.Tests/CollectionSegmentTypeTests.cs

What is expected?

Every field of the connection and collection segment types is parallel executable:
pageInfo: True, edges: True, nodes: True, totalCount: True
pageInfo: True, items: True, totalCount: Tru

What is actually happening?

edges, nodes and totalCount (connection) and items and totalCount (collection segment) are
not parallel executable, so their selections get SelectionExecutionStrategy.Serial.

Cause:

• ConnectionType.CreateConfiguration (lines 185, 196, 209 on main) and
  CollectionSegmentType (lines 102, 111) create each field with
  new ObjectFieldConfiguration(..., pureResolver: ...) { Flags = CoreFieldFlags.X }.
• The constructor sets IsParallelExecutable = true, which is a bit in Flags, and the object
  initializer then replaces Flags, clearing the bit.
• ObjectField only restores it when a pure resolver is compiled ("by definition, fields with
  pure resolvers are parallel executable", ObjectField.cs lines 205-209).
• That only happens when IsPureContext() holds (line 258): no global field middleware and no
  field middleware.

So any schema with global field middleware executes these fields serially.

Relevant log output

ConnectionTypeTests (unfixed):
    pageInfo: True
  - edges: True
  - nodes: True
  - totalCount: True
  + edges: False
  + nodes: False
  + totalCount: False

CollectionSegmentTypeTests (unfixed):
  - items: True
  - totalCount: True
  + items: False
  + totalCount: False

Additional context

• Same defect as DataLoader used inside node resolvers do not batch #7635, fixed by Added missing ParallelExecutable flag to node and nodes fields #7661 for the node and nodes fields only. That fix is the
  idiom NodeFieldTypeInterceptor still uses (lines 177 and 236):
  Flags = CoreFieldFlags.ParallelExecutable | CoreFieldFlags.GlobalIdNodeField
• Impact: paged results execute through the serial path. With [UsePaging] + [UseProjection] that includes the internal _combinedSelectionSet selection that resolves nodes. Combined with Request hangs forever when a serial task's id is reassigned before the scheduler waits for it #10561, this made paged queries hang under concurrent load in our services.