Drop Swift 5.5 (#197)

Motivation

Per SwiftNIO's formal version policy, we are ready to drop support for
Swift 5.5.

Modifications

This patch removes the support for 5.5 and all supporting
infrastructure. This includes the test generation functionality, which
is no longer required, as well as the files generated by that
functionality. It updates the dockerfile for 5.8, and it removes all
conditional compilation checks that are now definitionally true.

Result

A nice, clean, 5.6+ codebase

Author: Lukasa

[email protected]

@@ -14,7 +14,7 @@ All code will go through code review like in the other repositories related to t
 `swift-nio-extras` part of the SwiftNIO 2 family of repositories and depends on the following:
 
 - [`swift-nio`](https://github.com/apple/swift-nio), version 2.30.0 or better.
-- Swift 5.5.2
+- Swift 5.6
 - `zlib` and its development headers installed on the system. But don't worry, you'll find `zlib` on pretty much any UNIX system that can compile any sort of code.
 
 To depend on `swift-nio-extras`, put the following in the `dependencies` of your `Package.swift`:
@@ -25,14 +25,15 @@ To depend on `swift-nio-extras`, put the following in the `dependencies` of your
 
 ### Support for older Swift versions
 
-The most recent versions of SwiftNIO Extras support Swift 5.5.2 and newer. The minimum Swift version supported by SwiftNIO Extras releases are detailed below:
+The most recent versions of SwiftNIO Extras support Swift 5.6 and newer. The minimum Swift version supported by SwiftNIO Extras releases are detailed below:
 
 SwiftNIO Extras     | Minimum Swift Version
 --------------------|----------------------
 `1.0.0 ..< 1.10.0`  | 5.0
 `1.10.0 ..< 1.11.0` | 5.2
 `1.11.0 ..< 1.14.0` | 5.4
-`1.14.0 ...`        | 5.5.2
+`1.14.0 ..< 1.19.1` | 5.5.2
+`1.19.0 ...`        | 5.6
 
 On the [`nio-extras-0.1`](https://github.com/apple/swift-nio-extras/tree/nio-extras-0.1) branch, you can find the `swift-nio-extras` version for the SwiftNIO 1 family. It requires Swift 4.1 or better.
 

README.md

@@ -175,7 +175,5 @@ public class DebugInboundEventsHandler: ChannelInboundHandler {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension DebugInboundEventsHandler: Sendable {}
-#endif

Sources/NIOExtras/DebugInboundEventsHandler.swift

@@ -171,7 +171,5 @@ public class DebugOutboundEventsHandler: ChannelOutboundHandler {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension DebugOutboundEventsHandler: Sendable {}
-#endif

Sources/NIOExtras/DebugOutboundEventsHandler.swift

@@ -77,7 +77,5 @@ public final class FixedLengthFrameDecoder: ByteToMessageDecoder {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension FixedLengthFrameDecoder: Sendable {}
-#endif

Sources/NIOExtras/FixedLengthFrameDecoder.swift

@@ -217,10 +217,8 @@ extension String {
 
 
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension NIOJSONRPCFraming.ContentLengthHeaderFrameDecoder: Sendable {}
 
 @available(*, unavailable)
 extension NIOJSONRPCFraming.ContentLengthHeaderFrameEncoder: Sendable {}
-#endif

Sources/NIOExtras/JSONRPCFraming+ContentLengthHeader.swift

@@ -247,7 +247,5 @@ public final class LengthFieldBasedFrameDecoder: ByteToMessageDecoder {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension LengthFieldBasedFrameDecoder: Sendable {}
-#endif

Sources/NIOExtras/LengthFieldBasedFrameDecoder.swift

@@ -145,7 +145,5 @@ public final class LengthFieldPrepender: ChannelOutboundHandler {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension LengthFieldPrepender: Sendable {}
-#endif

Sources/NIOExtras/LengthFieldPrepender.swift

@@ -92,7 +92,5 @@ public class LineBasedFrameDecoder: ByteToMessageDecoder {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension LineBasedFrameDecoder: Sendable {}
-#endif

Sources/NIOExtras/LineBasedFrameDecoder.swift

@@ -97,7 +97,5 @@ public class NIOPCAPRingBuffer {
     }
 }
 
-#if swift(>=5.6)
 @available(*, unavailable)
 extension NIOPCAPRingBuffer: Sendable {}
-#endif