provide _NIO1APIShims (#758)

Motivation:

For package authors, the NIO1 to 2 transition can be taxing because we
keep changing things. So far, the community has done an incredible job
keeping up with our changes but we'd like to make it as easy as possible
continuing to do so.

Modifications:

- add a `_NIO1APIShims` module that when imported tries to provide some
  of the NIO1 API in NIO2 with helpful fixup messages

Result:

easier transition from NIO1 to NIO2

Package.swift

@@ -16,6 +16,8 @@
 import PackageDescription
 
 var targets: [PackageDescription.Target] = [
+    .target(name: "_NIO1APIShims",
+            dependencies: ["NIO", "NIOHTTP1", "NIOTLS"]),
     .target(name: "NIO",
             dependencies: ["CNIOLinux",
                            "CNIODarwin",
@@ -82,6 +84,7 @@ let package = Package(
                     targets: ["NIOPerformanceTester"]),
         .executable(name: "NIOMulticastChat", targets: ["NIOMulticastChat"]),
         .library(name: "NIO", targets: ["NIO"]),
+        .library(name: "_NIO1APIShims", targets: ["_NIO1APIShims"]),
         .library(name: "NIOTLS", targets: ["NIOTLS"]),
         .library(name: "NIOHTTP1", targets: ["NIOHTTP1"]),
         .library(name: "NIOConcurrencyHelpers", targets: ["NIOConcurrencyHelpers"]),

Sources/_NIO1APIShims/NIO1APIShims.swift

@@ -0,0 +1,196 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2017-2018 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import NIO
+import NIOHTTP1
+import NIOTLS
+
+#if !NIO_CI_BUILD
+#warning("""
+         If you are a user: Please ignore this warning, it's the SwiftNIO team's fault.
+
+         If you are developer of a package depending on NIO:
+            You're using NIO 2's 'NIO1 API Shims' module.
+            Please note that _NIO1APIShimsHelpers is a transitional module that is untested and
+            is not part of the public API. Before NIO 2.0.0 gets released it's still very useful
+            to `import _NIO1APIShimsHelpers` because it will make it easier for you to keep up
+            with NIO2 API changes until the API will stabilise and we will start tagging versions.
+
+            Sorry for causing you extra work but we believe the public API changes we're introducing
+            will eventually help us all becoming a better ecosystem.
+
+            💜 the SwiftNIO team.
+        """)
+#endif
+
+@available(*, deprecated, message: "ContiguousCollection does not exist in NIO2")
+public protocol ContiguousCollection: Collection {
+    func withUnsafeBytes<R>(_ body: (UnsafeRawBufferPointer) throws -> R) rethrows -> R
+}
+
+@available(*, deprecated, renamed: "SNIResult")
+public typealias SniResult = SNIResult
+
+@available(*, deprecated, renamed: "SNIHandler")
+public typealias SniHandler = SNIHandler
+
+@available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+extension StaticString: Collection {
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public typealias Element = UInt8
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public typealias SubSequence = ArraySlice<UInt8>
+
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public typealias _Index = Int
+
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public var startIndex: _Index { return 0 }
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public var endIndex: _Index { return self.utf8CodeUnitCount }
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public func index(after i: _Index) -> _Index { return i + 1 }
+
+    @available(*, deprecated, message: "don't use the StaticString: Collection extension please")
+    public subscript(position: Int) -> UInt8 {
+        precondition(position < self.utf8CodeUnitCount, "index \(position) out of bounds")
+        return self.utf8Start.advanced(by: position).pointee
+    }
+}
+
+extension ChannelPipeline {
+    @available(*, deprecated, message: "please use ByteToMessageHandler(myByteToMessageDecoder)")
+    public func add<Decoder: ByteToMessageDecoder>(handler decoder: Decoder) -> EventLoopFuture<Void> {
+        return self.add(handler: ByteToMessageHandler(decoder))
+    }
+}
+
+extension EventLoop {
+    @available(*, deprecated, renamed: "makePromise")
+    public func newPromise<T>(of type: T.Type = T.self, file: StaticString = #file, line: UInt = #line) -> EventLoopPromise<T> {
+        return self.makePromise(of: type, file: file, line: line)
+    }
+
+    @available(*, deprecated, renamed: "makeSucceededFuture")
+    public func newSucceededFuture<T>(result: T) -> EventLoopFuture<T> {
+        return self.makeSucceededFuture(result: result)
+    }
+
+    @available(*, deprecated, renamed: "makeFailedFuture")
+    public func newFailedFuture<T>(error: Error) -> EventLoopFuture<T> {
+        return self.makeFailedFuture(error: error)
+    }
+}
+
+extension EventLoopFuture {
+    @available(*, deprecated, message: "whenComplete now gets Result<T, Error>")
+    public func whenComplete(_ body: @escaping () -> Void) {
+        self.whenComplete { (_: Result) in
+            body()
+        }
+    }
+}
+
+extension EventLoopGroup {
+    @available(*, deprecated, message: "makeIterator is now required")
+    public func makeIterator() -> NIO.EventLoopIterator {
+        return .init([])
+    }
+}
+
+extension MarkedCircularBuffer {
+    @available(*, deprecated, message: "hasMark is now a property, remove `()`")
+    public func hasMark() -> Bool {
+        return self.hasMark
+    }
+
+    @available(*, deprecated, message: "markedElement is now a property, remove `()`")
+    public func markedElement() -> Element? {
+        return self.markedElement
+    }
+
+    @available(*, deprecated, message: "markedElementIndex is now a property, remove `()`")
+    public func markedElementIndex() -> Int? {
+        return self.markedElementIndex
+    }
+}
+
+extension HTTPVersion {
+    @available(*, deprecated, message: "type of major and minor is now Int")
+    public init(major: UInt16, minor: UInt16) {
+        self = .init(major: Int(major), minor: Int(minor))
+    }
+
+    @available(*, deprecated, message: "type of major is now Int")
+    public var majorLegacy: UInt16 {
+        return UInt16(self.major)
+    }
+
+    @available(*, deprecated, message: "type of minor is now Int")
+    public var minorLegacy: UInt16 {
+        return UInt16(self.minor)
+    }
+}
+
+@available(*, deprecated, renamed: "ChannelError")
+public enum ChannelLifecycleError {
+    @available(*, deprecated, message: "ChannelLifecycleError values are now available on ChannelError")
+    public static var inappropriateOperationForState: ChannelError {
+        return ChannelError.inappropriateOperationForState
+    }
+
+}
+
+@available(*, deprecated, renamed: "ChannelError")
+public enum MulticastError {
+    @available(*, deprecated, message: "MulticastError values are now available on ChannelError")
+    public static var unknownLocalAddress: ChannelError {
+        return .unknownLocalAddress
+    }
+
+    @available(*, deprecated, message: "MulticastError values are now available on ChannelError")
+    public static var badMulticastGroupAddressFamily: ChannelError {
+        return .badMulticastGroupAddressFamily
+    }
+
+    @available(*, deprecated, message: "MulticastError values are now available on ChannelError")
+    public static var badInterfaceAddressFamily: ChannelError {
+        return .badInterfaceAddressFamily
+    }
+
+    @available(*, deprecated, message: "MulticastError values are now available on ChannelError")
+    public static func illegalMulticastAddress(_ address: SocketAddress) -> ChannelError {
+        return .illegalMulticastAddress(address)
+    }
+}
+
+extension ChannelError {
+    @available(*, deprecated, message: "ChannelError.connectFailed has been removed")
+    public static var connectFailed: NIOConnectionError {
+        fatalError("ChannelError.connectFailed has been removed in NIO2")
+    }
+}
+
+
+extension SocketAddress {
+    @available(*, deprecated, message: "type of port is now Int?")
+    public var portLegacy: UInt16? {
+        return self.port.map(UInt16.init)
+    }
+
+    @available(*, deprecated, renamed: "makeAddressResolvingHost")
+    public static func newAddressResolving(host: String, port: Int) throws -> SocketAddress {
+        return try self.makeAddressResolvingHost(host, port: port)
+    }
+}