[C++] Create AsyncGenerator from Future<AsyncGenerator<T>> #28092
Description
This is useful for doing things like...
Future vec_fut = GetVectorOfThingsAsync();
Future<AsyncGenerator> gen_fut = vec_fut.Then([] (const SomeVector& vec) { return MakeVectorGenerator(vec); };
AsyncGenerator item_gen = MakeFutureFirstGenerator(gen_fut);
The cost of the initial future is just part of the cost of getting the first item from the generator.
Reporter: Weston Pace / @westonpace
Assignee: Weston Pace / @westonpace
PRs and other links:
Note: This issue was originally created as ARROW-12286. Please see the migration documentation for further details.