Fixed GRPCCore issues when enabling explicit-sendable rule.

Author: rafaelcepeda

Package.swift

@@ -65,6 +65,7 @@ let defaultSwiftSettings: [SwiftSetting] =
     .enableUpcomingFeature("ExistentialAny"),
     .enableUpcomingFeature("InternalImportsByDefault"),
     .enableUpcomingFeature("MemberImportVisibility"),
+    .unsafeFlags(["-Xfrontend", "-require-explicit-sendable"]),
   ]
 
 // -------------------------------------------------------------------------------------------------

Sources/GRPCCore/Call/Client/Internal/ClientRPCExecutor+HedgingExecutor.swift

@@ -501,7 +501,7 @@ extension ClientRPCExecutor.HedgingExecutor {
   }
 
   @usableFromInline
-  struct ScheduledState {
+  struct ScheduledState: Sendable {
     @usableFromInline
     var _handle: CancellableTaskHandle?
     @usableFromInline

Sources/GRPCCore/Call/Client/Internal/ClientRPCExecutor.swift

@@ -16,7 +16,7 @@
 
 @available(gRPCSwift 2.0, *)
 @usableFromInline
-enum ClientRPCExecutor {
+enum ClientRPCExecutor: Sendable {
   /// Execute the request and handle its response.
   ///
   /// - Parameters:

Sources/GRPCCore/Call/Client/Internal/ClientStreamExecutor.swift

@@ -16,7 +16,7 @@
 
 @available(gRPCSwift 2.0, *)
 @usableFromInline
-internal enum ClientStreamExecutor {
+internal enum ClientStreamExecutor: Sendable {
   /// Execute a request on the stream executor.
   ///
   /// - Parameters:
@@ -250,3 +250,6 @@ internal enum ClientStreamExecutor {
     }
   }
 }
+
+@available(*, unavailable)
+extension ClientStreamExecutor.RawBodyPartToMessageSequence.AsyncIterator: Sendable {}

Sources/GRPCCore/Call/Client/Internal/RetryDelaySequence.swift

@@ -27,7 +27,7 @@ public import Musl  // should be @usableFromInline
 
 @available(gRPCSwift 2.0, *)
 @usableFromInline
-struct RetryDelaySequence: Sequence {
+struct RetryDelaySequence: Sequence, Sendable {
   @usableFromInline
   typealias Element = Duration
 
@@ -45,7 +45,7 @@ struct RetryDelaySequence: Sequence {
   }
 
   @usableFromInline
-  struct Iterator: IteratorProtocol {
+  struct Iterator: IteratorProtocol, Sendable {
     @usableFromInline
     let policy: RetryPolicy
     @usableFromInline

Sources/GRPCCore/Call/Server/Internal/ServerRPCExecutor.swift

@@ -16,7 +16,7 @@
 
 @available(gRPCSwift 2.0, *)
 @usableFromInline
-struct ServerRPCExecutor {
+struct ServerRPCExecutor: Sendable {
   /// Executes an RPC using the provided handler.
   ///
   /// - Parameters:
@@ -272,7 +272,7 @@ struct ServerRPCExecutor {
   }
 
   @usableFromInline
-  enum OnFirstRequestPart<Bytes: GRPCContiguousBytes> {
+  enum OnFirstRequestPart<Bytes: GRPCContiguousBytes>: Sendable {
     case process(
       Metadata,
       UnsafeTransfer<RPCAsyncSequence<RPCRequestPart<Bytes>, any Error>.AsyncIterator>

Sources/GRPCCore/Coding/CompressionAlgorithm.swift

@@ -94,7 +94,7 @@ extension CompressionAlgorithmSet {
   }
 
   /// A sequence of ``CompressionAlgorithm`` values present in a ``CompressionAlgorithmSet``.
-  public struct Elements: Sequence {
+  public struct Elements: Sequence, Sendable {
     public typealias Element = CompressionAlgorithm
 
     private let algorithmSet: CompressionAlgorithmSet
@@ -107,7 +107,7 @@ extension CompressionAlgorithmSet {
       return Iterator(algorithmSet: self.algorithmSet)
     }
 
-    public struct Iterator: IteratorProtocol {
+    public struct Iterator: IteratorProtocol, Sendable {
       private let algorithmSet: CompressionAlgorithmSet
       private var iterator: IndexingIterator<[CompressionAlgorithm.Value]>
 

Sources/GRPCCore/Streaming/Internal/AsyncSequenceOfOne.swift

@@ -49,7 +49,7 @@ struct AsyncSequenceOfOne<Element: Sendable, Failure: Error>: AsyncSequence, Sen
   }
 
   @usableFromInline
-  struct AsyncIterator: AsyncIteratorProtocol {
+  struct AsyncIterator: AsyncIteratorProtocol, Sendable {
     @usableFromInline
     private(set) var result: Result<Element, Failure>?
 

Sources/GRPCCore/Streaming/Internal/BroadcastAsyncSequence.swift

@@ -89,7 +89,7 @@ struct BroadcastAsyncSequence<Element: Sendable>: Sendable, AsyncSequence {
 @available(gRPCSwift 2.0, *)
 extension BroadcastAsyncSequence {
   @usableFromInline
-  struct AsyncIterator: AsyncIteratorProtocol {
+  struct AsyncIterator: AsyncIteratorProtocol, Sendable {
     @usableFromInline
     let _storage: _BroadcastSequenceStorage<Element>
     @usableFromInline
@@ -1204,7 +1204,7 @@ struct _BroadcastSequenceStateMachine<Element: Sendable>: Sendable {
   }
 
   @usableFromInline
-  enum OnCancelSubscription {
+  enum OnCancelSubscription: Sendable {
     case none
     case resume(ConsumerContinuation, Result<Element?, any Error>)
   }
@@ -1244,7 +1244,7 @@ struct _BroadcastSequenceStateMachine<Element: Sendable>: Sendable {
   }
 
   @usableFromInline
-  enum OnSubscribe {
+  enum OnSubscribe: Sendable {
     case subscribed(_BroadcastSequenceStateMachine<Element>.Subscriptions.ID)
   }
 
@@ -1282,7 +1282,7 @@ struct _BroadcastSequenceStateMachine<Element: Sendable>: Sendable {
   }
 
   @usableFromInline
-  enum OnWaitToProduceMore {
+  enum OnWaitToProduceMore: Sendable {
     case none
     case resume(ProducerContinuation, Result<Void, any Error>)
   }
@@ -1498,7 +1498,7 @@ extension _BroadcastSequenceStateMachine {
     }
 
     @usableFromInline
-    enum ElementLookup {
+    enum ElementLookup: Sendable {
       /// The element was found in the collection.
       case found(Element)
       /// The element isn't in the collection, but it could be in the future.
@@ -1810,3 +1810,33 @@ extension _BroadcastSequenceStateMachine {
     case many([Value])
   }
 }
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.ConsumerContinuations: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.ProducerContinuations: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnInvalidateAllSubscriptions: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnYield: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnFinish: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnNext: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnNext.ReturnAndResumeProducers: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnSetContinuation: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine.OnDropResources: Sendable {}
+
+@available(*, unavailable)
+extension _BroadcastSequenceStateMachine._OneOrMany: Sendable {}

Sources/GRPCCore/Streaming/Internal/UncheckedAsyncIteratorSequence.swift

@@ -80,3 +80,6 @@ final class UncheckedAsyncIteratorSequence<
     return AsyncIterator(base: self.base)
   }
 }
+
+@available(*, unavailable)
+extension UncheckedAsyncIteratorSequence.AsyncIterator: Sendable {}