From 62684e2d1f23a220aada9e7252eacb856cdc79ab Mon Sep 17 00:00:00 2001
From: Franz Busch <f.busch@apple.com>
Date: Mon, 14 Oct 2024 16:15:06 +0100
Subject: [PATCH 1/3] Drop support for Swift 5.8

# Motivation

We only support the last three Swift released versions which are at this time 5.9, 5.10 and 6.

# Modification

This PR drops anything related to Swift 5.8.

# Result

Version support aligned.
---
 .../5.8/NIOCoreBenchmarks.NIOAsyncChannel.init.p90.json  | 3 ---
 .../Thresholds/5.8/NIOPosixBenchmarks.TCPEcho.p90.json   | 3 ---
 CONTRIBUTING.md                                          | 2 +-
 Package.swift                                            | 2 +-
 README.md                                                | 5 +++--
 Sources/NIOCore/EventLoop+SerialExecutor.swift           | 2 --
 Sources/NIOCore/EventLoop.swift                          | 4 ----
 Sources/NIOCore/NIOScheduledCallback.swift               | 3 +--
 Sources/NIOEmbedded/AsyncTestingEventLoop.swift          | 2 --
 Sources/NIOEmbedded/Embedded.swift                       | 2 --
 Sources/NIOPosix/MultiThreadedEventLoopGroup.swift       | 2 --
 .../NIOPosix/PosixSingletons+ConcurrencyTakeOver.swift   | 2 --
 Sources/NIOPosix/SelectableEventLoop.swift               | 6 ------
 Sources/NIOTCPEchoClient/Client.swift                    | 9 ---------
 Sources/NIOTCPEchoServer/Server.swift                    | 9 ---------
 Tests/NIOPosixTests/SerialExecutorTests.swift            | 7 -------
 16 files changed, 6 insertions(+), 57 deletions(-)
 delete mode 100644 Benchmarks/Thresholds/5.8/NIOCoreBenchmarks.NIOAsyncChannel.init.p90.json
 delete mode 100644 Benchmarks/Thresholds/5.8/NIOPosixBenchmarks.TCPEcho.p90.json

diff --git a/Benchmarks/Thresholds/5.8/NIOCoreBenchmarks.NIOAsyncChannel.init.p90.json b/Benchmarks/Thresholds/5.8/NIOCoreBenchmarks.NIOAsyncChannel.init.p90.json
deleted file mode 100644
index ec2d0ad0f8..0000000000
--- a/Benchmarks/Thresholds/5.8/NIOCoreBenchmarks.NIOAsyncChannel.init.p90.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "mallocCountTotal" : 8000
-}
\ No newline at end of file
diff --git a/Benchmarks/Thresholds/5.8/NIOPosixBenchmarks.TCPEcho.p90.json b/Benchmarks/Thresholds/5.8/NIOPosixBenchmarks.TCPEcho.p90.json
deleted file mode 100644
index 8517c2fe45..0000000000
--- a/Benchmarks/Thresholds/5.8/NIOPosixBenchmarks.TCPEcho.p90.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "mallocCountTotal" : 556
-}
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 280f2b7a4f..ec9f46f020 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -67,7 +67,7 @@ The default policy for taking contributions is “Squash and Merge” - because
 
 ### Make sure your patch works for all supported versions of swift
 
-The CI will do this for you, but a project maintainer must kick it off for you.  Currently all versions of Swift >= 5.8 are supported.
+The CI will do this for you, but a project maintainer must kick it off for you.  Currently all versions of Swift >= 5.9 are supported.
 
 If you wish to test this locally you have two options [act](https://github.com/nektos/act) and Docker Compose files.
 
diff --git a/Package.swift b/Package.swift
index c5edd5ebf1..99842452b9 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:5.8
+// swift-tools-version:5.9
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the SwiftNIO open source project
diff --git a/README.md b/README.md
index 699b607ac3..42b20a37cb 100644
--- a/README.md
+++ b/README.md
@@ -76,7 +76,7 @@ This is the current version of SwiftNIO and will be supported for the foreseeabl
 We commit to support the most recently released swift version (currently 5.10) and the last two minor releases before that unless this is impossible to do in one codebase.
 In addition checks are run against the latest beta release (if any) as well as the nightly swift builds and the intent is that these should pass. 
 
-The most recent versions of SwiftNIO support Swift 5.8 and newer. The minimum Swift version supported by SwiftNIO releases are detailed below:
+The most recent versions of SwiftNIO support Swift 5.9 and newer. The minimum Swift version supported by SwiftNIO releases are detailed below:
 
 SwiftNIO            | Minimum Swift Version
 --------------------|----------------------
@@ -86,7 +86,8 @@ SwiftNIO            | Minimum Swift Version
 `2.43.0 ..< 2.51.0` | 5.5.2
 `2.51.0 ..< 2.60.0` | 5.6
 `2.60.0 ..< 2.65.0` | 5.7
-`2.65.0 ...`        | 5.8
+`2.65.0 ..< 2.75.0  | 5.8
+`2.75.0 ...`        | 5.9
 
 ### SwiftNIO 1
 SwiftNIO 1 is considered end of life - it is strongly recommended that you move to a newer version.  The Core NIO team does not actively work on this version.  No new features will be added to this version but PRs which fix bugs or security vulnerabilities will be accepted until the end of May 2022.
diff --git a/Sources/NIOCore/EventLoop+SerialExecutor.swift b/Sources/NIOCore/EventLoop+SerialExecutor.swift
index 2fc92f1f1a..d8486a59a1 100644
--- a/Sources/NIOCore/EventLoop+SerialExecutor.swift
+++ b/Sources/NIOCore/EventLoop+SerialExecutor.swift
@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.9)
 /// A helper protocol that can be mixed in to a NIO ``EventLoop`` to provide an
 /// automatic conformance to `SerialExecutor`.
 ///
@@ -91,4 +90,3 @@ extension NIODefaultSerialEventLoopExecutor: SerialExecutor {
         self.loop === other.loop
     }
 }
-#endif
diff --git a/Sources/NIOCore/EventLoop.swift b/Sources/NIOCore/EventLoop.swift
index 171a757ba9..4e76abe821 100644
--- a/Sources/NIOCore/EventLoop.swift
+++ b/Sources/NIOCore/EventLoop.swift
@@ -317,7 +317,6 @@ public protocol EventLoop: EventLoopGroup {
     /// allows `EventLoop`s to cache a pre-succeeded `Void` future to prevent superfluous allocations.
     func makeSucceededVoidFuture() -> EventLoopFuture<Void>
 
-    #if compiler(>=5.9)
     /// Returns a `SerialExecutor` corresponding to this ``EventLoop``.
     ///
     /// This executor can be used to isolate an actor to a given ``EventLoop``. Implementers are encouraged to customise
@@ -330,7 +329,6 @@ public protocol EventLoop: EventLoopGroup {
     /// Submit a job to be executed by the `EventLoop`
     @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
     func enqueue(_ job: consuming ExecutorJob)
-    #endif
 
     /// Must crash if it is not safe to call `wait()` on an `EventLoopFuture`.
     ///
@@ -415,7 +413,6 @@ extension EventLoop {
 }
 
 extension EventLoop {
-    #if compiler(>=5.9)
     @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
     public var executor: any SerialExecutor {
         NIODefaultSerialEventLoopExecutor(self)
@@ -432,7 +429,6 @@ extension EventLoop {
             unownedJob.runSynchronously(on: self.executor.asUnownedSerialExecutor())
         }
     }
-    #endif
 }
 
 extension EventLoopGroup {
diff --git a/Sources/NIOCore/NIOScheduledCallback.swift b/Sources/NIOCore/NIOScheduledCallback.swift
index 84c9f8d202..8d7a056a0a 100644
--- a/Sources/NIOCore/NIOScheduledCallback.swift
+++ b/Sources/NIOCore/NIOScheduledCallback.swift
@@ -89,8 +89,7 @@ public struct NIOScheduledCallback: Sendable {
 }
 
 extension EventLoop {
-    // This could be package once we drop Swift 5.8.
-    public func _scheduleCallback(
+    package func _scheduleCallback(
         at deadline: NIODeadline,
         handler: some NIOScheduledCallbackHandler
     ) -> NIOScheduledCallback {
diff --git a/Sources/NIOEmbedded/AsyncTestingEventLoop.swift b/Sources/NIOEmbedded/AsyncTestingEventLoop.swift
index 959b4bb343..52d56bf9ca 100644
--- a/Sources/NIOEmbedded/AsyncTestingEventLoop.swift
+++ b/Sources/NIOEmbedded/AsyncTestingEventLoop.swift
@@ -407,10 +407,8 @@ public final class NIOAsyncTestingEventLoop: EventLoop, @unchecked Sendable {
 }
 
 // MARK: SerialExecutor conformance
-#if compiler(>=5.9)
 @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
 extension NIOAsyncTestingEventLoop: NIOSerialEventLoopExecutor {}
-#endif
 
 /// This is a thread-safe promise creation store.
 ///
diff --git a/Sources/NIOEmbedded/Embedded.swift b/Sources/NIOEmbedded/Embedded.swift
index 93e90bfe54..a6c2b33b5b 100644
--- a/Sources/NIOEmbedded/Embedded.swift
+++ b/Sources/NIOEmbedded/Embedded.swift
@@ -271,14 +271,12 @@ public final class EmbeddedEventLoop: EventLoop, CustomStringConvertible {
         precondition(scheduledTasks.isEmpty, "Embedded event loop freed with unexecuted scheduled tasks!")
     }
 
-    #if compiler(>=5.9)
     @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
     public var executor: any SerialExecutor {
         fatalError(
             "EmbeddedEventLoop is not thread safe and cannot be used as a SerialExecutor. Use NIOAsyncTestingEventLoop instead."
         )
     }
-    #endif
 }
 
 @usableFromInline
diff --git a/Sources/NIOPosix/MultiThreadedEventLoopGroup.swift b/Sources/NIOPosix/MultiThreadedEventLoopGroup.swift
index c188e8ef69..6e20a9a98c 100644
--- a/Sources/NIOPosix/MultiThreadedEventLoopGroup.swift
+++ b/Sources/NIOPosix/MultiThreadedEventLoopGroup.swift
@@ -489,7 +489,6 @@ extension MultiThreadedEventLoopGroup: CustomStringConvertible {
     }
 }
 
-#if compiler(>=5.9)
 @usableFromInline
 struct ErasedUnownedJob {
     @usableFromInline
@@ -507,7 +506,6 @@ struct ErasedUnownedJob {
         self.erasedJob as! UnownedJob
     }
 }
-#endif
 
 @usableFromInline
 internal struct ScheduledTask {
diff --git a/Sources/NIOPosix/PosixSingletons+ConcurrencyTakeOver.swift b/Sources/NIOPosix/PosixSingletons+ConcurrencyTakeOver.swift
index e56242b12b..07ee8955ce 100644
--- a/Sources/NIOPosix/PosixSingletons+ConcurrencyTakeOver.swift
+++ b/Sources/NIOPosix/PosixSingletons+ConcurrencyTakeOver.swift
@@ -15,14 +15,12 @@
 import Atomics
 import NIOCore
 
-#if compiler(>=5.9)
 private protocol SilenceWarning {
     @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
     func enqueue(_ job: UnownedJob)
 }
 @available(macOS 14, *)
 extension SelectableEventLoop: SilenceWarning {}
-#endif
 
 private let _haveWeTakenOverTheConcurrencyPool = ManagedAtomic(false)
 extension NIOSingletons {
diff --git a/Sources/NIOPosix/SelectableEventLoop.swift b/Sources/NIOPosix/SelectableEventLoop.swift
index 79ba55b6c8..2ec9c71605 100644
--- a/Sources/NIOPosix/SelectableEventLoop.swift
+++ b/Sources/NIOPosix/SelectableEventLoop.swift
@@ -353,7 +353,6 @@ internal final class SelectableEventLoop: EventLoop {
         try? self._schedule0(.immediate(.function(task)))
     }
 
-    #if compiler(>=5.9)
     @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
     @usableFromInline
     func enqueue(_ job: consuming ExecutorJob) {
@@ -361,7 +360,6 @@ internal final class SelectableEventLoop: EventLoop {
         let erasedJob = ErasedUnownedJob(job: UnownedJob(job))
         try? self._schedule0(.immediate(.unownedJob(erasedJob)))
     }
-    #endif
 
     /// Add the `ScheduledTask` to be executed.
     @usableFromInline
@@ -901,17 +899,13 @@ extension SelectableEventLoop: CustomStringConvertible, CustomDebugStringConvert
 }
 
 // MARK: SerialExecutor conformance
-#if compiler(>=5.9)
 @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
 extension SelectableEventLoop: NIOSerialEventLoopExecutor {}
-#endif
 
 @usableFromInline
 enum UnderlyingTask {
     case function(() -> Void)
-    #if compiler(>=5.9)
     case unownedJob(ErasedUnownedJob)
-    #endif
     case callback(any NIOScheduledCallbackHandler)
 }
 
diff --git a/Sources/NIOTCPEchoClient/Client.swift b/Sources/NIOTCPEchoClient/Client.swift
index e624a78667..67f917e9da 100644
--- a/Sources/NIOTCPEchoClient/Client.swift
+++ b/Sources/NIOTCPEchoClient/Client.swift
@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.9)
 import NIOCore
 import NIOPosix
 
@@ -112,11 +111,3 @@ private final class NewlineDelimiterCoder: ByteToMessageDecoder, MessageToByteEn
         out.writeInteger(self.newLine)
     }
 }
-#else
-@main
-struct Client {
-    static func main() {
-        fatalError("Requires at least Swift 5.9")
-    }
-}
-#endif
diff --git a/Sources/NIOTCPEchoServer/Server.swift b/Sources/NIOTCPEchoServer/Server.swift
index c8f2200410..6f0d98c1b8 100644
--- a/Sources/NIOTCPEchoServer/Server.swift
+++ b/Sources/NIOTCPEchoServer/Server.swift
@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=5.9)
 import NIOCore
 import NIOPosix
 
@@ -122,11 +121,3 @@ private final class NewlineDelimiterCoder: ByteToMessageDecoder, MessageToByteEn
         out.writeInteger(self.newLine)
     }
 }
-#else
-@main
-struct Server {
-    static func main() {
-        fatalError("Requires at least Swift 5.9")
-    }
-}
-#endif
diff --git a/Tests/NIOPosixTests/SerialExecutorTests.swift b/Tests/NIOPosixTests/SerialExecutorTests.swift
index 8df2ed6be0..0ec3994f9c 100644
--- a/Tests/NIOPosixTests/SerialExecutorTests.swift
+++ b/Tests/NIOPosixTests/SerialExecutorTests.swift
@@ -16,7 +16,6 @@ import NIOEmbedded
 import NIOPosix
 import XCTest
 
-#if compiler(>=5.9)
 @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
 actor EventLoopBoundActor {
     nonisolated let unownedExecutor: UnownedSerialExecutor
@@ -45,19 +44,13 @@ actor EventLoopBoundActor {
     }
     #endif
 }
-#endif
 
 @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
 final class SerialExecutorTests: XCTestCase {
     private func _testBasicExecutorFitsOnEventLoop(loop1: EventLoop, loop2: EventLoop) async throws {
-        #if compiler(<5.9)
-        throw XCTSkip("Custom executors are only supported in 5.9")
-        #else
-
         let testActor = EventLoopBoundActor(loop: loop1)
         await testActor.assertInLoop(loop1)
         await testActor.assertNotInLoop(loop2)
-        #endif
     }
 
     func testBasicExecutorFitsOnEventLoop_MTELG() async throws {

From 84c4e15cca7d9d03fa46ee64db820035e714a861 Mon Sep 17 00:00:00 2001
From: Franz Busch <f.busch@apple.com>
Date: Mon, 14 Oct 2024 16:25:12 +0100
Subject: [PATCH 2/3] Disable warnings as errors on 6

---
 .github/workflows/main.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 113e35e6a2..1a971acf46 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -12,7 +12,7 @@ jobs:
     with:
       linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
       linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
-      linux_6_0_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
+      linux_6_0_arguments_override: "--explicit-target-dependency-import-check error"
       linux_nightly_6_0_arguments_override: "--explicit-target-dependency-import-check error"
       linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error"
 

From af2b4c54982bec84208792cabac3c56606aa290f Mon Sep 17 00:00:00 2001
From: Franz Busch <f.busch@apple.com>
Date: Tue, 15 Oct 2024 20:48:54 +0100
Subject: [PATCH 3/3] Review

---
 README.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 42b20a37cb..055c5359c3 100644
--- a/README.md
+++ b/README.md
@@ -74,7 +74,7 @@ This is the current version of SwiftNIO and will be supported for the foreseeabl
 ### Swift Versions
 
 We commit to support the most recently released swift version (currently 5.10) and the last two minor releases before that unless this is impossible to do in one codebase.
-In addition checks are run against the latest beta release (if any) as well as the nightly swift builds and the intent is that these should pass. 
+In addition checks are run against the latest beta release (if any) as well as the nightly swift builds and the intent is that these should pass.
 
 The most recent versions of SwiftNIO support Swift 5.9 and newer. The minimum Swift version supported by SwiftNIO releases are detailed below:
 
@@ -86,8 +86,8 @@ SwiftNIO            | Minimum Swift Version
 `2.43.0 ..< 2.51.0` | 5.5.2
 `2.51.0 ..< 2.60.0` | 5.6
 `2.60.0 ..< 2.65.0` | 5.7
-`2.65.0 ..< 2.75.0  | 5.8
-`2.75.0 ...`        | 5.9
+`2.65.0 ..< 2.76.0  | 5.8
+`2.76.0 ...`        | 5.9
 
 ### SwiftNIO 1
 SwiftNIO 1 is considered end of life - it is strongly recommended that you move to a newer version.  The Core NIO team does not actively work on this version.  No new features will be added to this version but PRs which fix bugs or security vulnerabilities will be accepted until the end of May 2022.