### Motivation:
Follow up PR for https://github.com/apple/swift-nio/pull/2399
We currently still return `nil` if the current `Task` is canceled before the first call to `NIOThrowingAsyncSequenceProducer.AsyncIterator.next()` but it should throw `CancellationError` too.
In addition, the generic `Failure` type turns out to be a problem. Just throwing a `CancellationError` without checking that `Failure` type is `any Swift.Error` or `CancellationError` introduced a type safety violation as we throw an unrelated type.
### Modifications:
- throw `CancellationError` on eager cancellation
- deprecates the generic `Failure` type of `NIOThrowingAsyncSequenceProducer`. It now must always be `any Swift.Error`. For backward compatibility we will still return nil if `Failure` is not `any Swift.Error` or `CancellationError`.
### Result:
`CancellationError` is now correctly thrown instead of returning `nil` on eager cancelation. Generic `Failure` type is deprecated.
Motivation:
Up until recently, it has not been possible to regression check our
documentation. However, in recent releases of the DocC plugin it has
become possible to make warnings into errors, making it possible for us
to CI our docs.
This patch adds support for doing that, and also cleans up our
documentation so that it successfully passes the check.
Along the way I accidentally wrote an `index.md` for `NIOCore` so I
figure we may as well keep it.
Modifications:
- Structure the documentation for NIOCore
- Fix up DocC issues
- Add `check-docs.sh` script to check the docs cleanly build
- Wire things up to our docker-compose scripts.
Result:
We can CI our docs.
Co-authored-by: George Barnett <gbarnett@apple.com>
# Motivation
Our `NIOAsyncSequenceProducer` is a unicast `AsyncSequence`; therefor, we must ensure that only a single iterator is every created. Our failure mode in the case another iterator is created is to `fatalError`. Currently, this `fatalError` is not produced if the sequence is in the `finished` state. This results in hard to debug behaviour since the user will get a basically useless iterator.
# Modification
Ensure that the `finished` state also keeps track of if an iterator was initialised and produces the correct `fatalError`.
# Result
We are now consistent in how many iterators can be created for every state.
* Call finish once the Source is deinited
# Motivation
We **MUST** call `finish()` when the `Source` deinits otherwise we can have a suspended continuation that never gets resumed.
# Modification
Introduce an internal class to both `Source`s and call `finish()` in their `deinit`s.
# Result
We are now resuming all continuations.
* Remove @unchecked
* Small changes for the `NIOAsyncSequenceProducer`
# Motivation
In the PR for the `NIOAsyncWriter`, a couple of comments around naming of `private` properties that needed to be `internal` due to inlinability and other smaller nits came up.
# Modification
This PR includes two things:
1. Fixing up of the small nits like using `_` or getting the imports inside the `#if` checks
2. Changing the public API of the `makeSequence` to be aligned across the throwing and non-throwing one.
# Result
Cleaner code and alinged APIs.
* Fix refactoring left-overs
* Add throwing version of `NIOAsyncSequenceProducer`
# Motivation
We recently introduced a `NIOAsyncSequenceProducer` to bridge a stream of elements from the NIO world into the async world. The introduced type was a non-throwing `AsyncSequence`. To support all use-cases we also need to offer a throwing variant of the type.
# Modification
- Introduce a new `NIOThrowingAsyncSequenceProducer` that is identical to the `NIOAsyncSequenceProducer` except that it has a `Failure` generic parameter and that the `next()` method is throwing.
- Extract the `StateMachine` from both `AsyncSequenceProducer`s and unify them.
- There is one modification in behaviour: `didTerminate` is now only called after `nil` or the error has been consumed from the sequence.
# Result
We now have a throwing variant of the `NIOAsyncSequenceProducer`.
* Code review and fix CI
* Remove duplicated code
Co-authored-by: Cory Benfield <lukasa@apple.com>
Fabian Fett