MiddlewareManager only decorates the first field encountered

[patrys]

get_middleware_resolvers is implemented as a generator:

https://github.com/graphql-python/graphql-core-next/blob/f6b078bddae4dd8a48ebf878a6fd5fbbac52bd1b/graphql/execution/middleware.py#L56-L58

The generator object is then assigned to self._middleware_resolvers:

https://github.com/graphql-python/graphql-core-next/blob/f6b078bddae4dd8a48ebf878a6fd5fbbac52bd1b/graphql/execution/middleware.py#L30-L32

As the generator is not consumed and unrolled into a list at this point, it is exhausted during the reduce() call of the first field construction:

https://github.com/graphql-python/graphql-core-next/blob/f6b078bddae4dd8a48ebf878a6fd5fbbac52bd1b/graphql/execution/middleware.py#L46-L50

As the generator is now exhausted, all other calls to reduce() will immediately receive StopIteration so no other field is wrapped.

[Cito]

Thanks @patrys - I can confirm the issue and your fix, and added a regression test for this.