Allow building on iOS 12

.swiftlint.yml

@@ -105,7 +105,7 @@ modifier_order:
     - dynamic
     - convenience
 deployment_target:
-  iOS_deployment_target: 13.0
+  iOS_deployment_target: 12.0
 
 custom_rules:
   newline_after_brace:

Examples/ElizaSharedSources/GeneratedSources/eliza.connect.swift

@@ -17,14 +17,17 @@ internal protocol Buf_Connect_Demo_Eliza_V1_ElizaServiceClientInterface {
 
     /// Say is a unary request demo. This method should allow for a one sentence
     /// response given a one sentence request.
+    @available(iOS 13, *)
     func `say`(request: Buf_Connect_Demo_Eliza_V1_SayRequest, headers: Connect.Headers) async -> ResponseMessage<Buf_Connect_Demo_Eliza_V1_SayResponse>
 
     /// Converse is a bi-directional streaming request demo. This method should allow for
     /// many requests and many responses.
+    @available(iOS 13, *)
     func `converse`(headers: Connect.Headers) -> any Connect.BidirectionalAsyncStreamInterface<Buf_Connect_Demo_Eliza_V1_ConverseRequest, Buf_Connect_Demo_Eliza_V1_ConverseResponse>
 
     /// Introduce is a server-streaming request demo.  This method allows for a single request that will return a series
     /// of responses
+    @available(iOS 13, *)
     func `introduce`(headers: Connect.Headers) -> any Connect.ServerOnlyAsyncStreamInterface<Buf_Connect_Demo_Eliza_V1_IntroduceRequest, Buf_Connect_Demo_Eliza_V1_IntroduceResponse>
 }
 
@@ -36,14 +39,17 @@ internal final class Buf_Connect_Demo_Eliza_V1_ElizaServiceClient: Buf_Connect_D
         self.client = client
     }
 
+    @available(iOS 13, *)
     internal func `say`(request: Buf_Connect_Demo_Eliza_V1_SayRequest, headers: Connect.Headers = [:]) async -> ResponseMessage<Buf_Connect_Demo_Eliza_V1_SayResponse> {
         return await self.client.unary(path: "buf.connect.demo.eliza.v1.ElizaService/Say", request: request, headers: headers)
     }
 
+    @available(iOS 13, *)
     internal func `converse`(headers: Connect.Headers = [:]) -> any Connect.BidirectionalAsyncStreamInterface<Buf_Connect_Demo_Eliza_V1_ConverseRequest, Buf_Connect_Demo_Eliza_V1_ConverseResponse> {
         return self.client.bidirectionalStream(path: "buf.connect.demo.eliza.v1.ElizaService/Converse", headers: headers)
     }
 
+    @available(iOS 13, *)
     internal func `introduce`(headers: Connect.Headers = [:]) -> any Connect.ServerOnlyAsyncStreamInterface<Buf_Connect_Demo_Eliza_V1_IntroduceRequest, Buf_Connect_Demo_Eliza_V1_IntroduceResponse> {
         return self.client.serverOnlyStream(path: "buf.connect.demo.eliza.v1.ElizaService/Introduce", headers: headers)
     }

Libraries/Connect/Implementation/ProtocolClient.swift

@@ -161,6 +161,7 @@ extension ProtocolClient: ProtocolClientInterface {
 
     // MARK: - Async/await
 
+    @available(iOS 13, *)
     public func unary<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(
@@ -173,6 +174,7 @@ extension ProtocolClient: ProtocolClientInterface {
         }.send()
     }
 
+    @available(iOS 13, *)
     public func bidirectionalStream<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(
@@ -186,6 +188,7 @@ extension ProtocolClient: ProtocolClientInterface {
         return bidirectionalAsync.configureForSending(with: callbacks)
     }
 
+    @available(iOS 13, *)
     public func clientOnlyStream<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(
@@ -199,6 +202,7 @@ extension ProtocolClient: ProtocolClientInterface {
         return bidirectionalAsync.configureForSending(with: callbacks)
     }
 
+    @available(iOS 13, *)
     public func serverOnlyStream<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(

Libraries/Connect/Implementation/Streaming/BidirectionalAsyncStream.swift

@@ -17,6 +17,7 @@ import SwiftProtobuf
 /// Concrete implementation of `BidirectionalAsyncStreamInterface`.
 /// Provides the necessary wiring to bridge from closures/callbacks to Swift's `AsyncStream`
 /// to work with async/await.
+@available(iOS 13, *)
 final class BidirectionalAsyncStream<Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message> {
     /// The underlying async stream that will be exposed to the consumer.
     /// Force unwrapped because it captures `self` on `init`.
@@ -81,6 +82,7 @@ final class BidirectionalAsyncStream<Input: SwiftProtobuf.Message, Output: Swift
     }
 }
 
+@available(iOS 13, *)
 extension BidirectionalAsyncStream: BidirectionalAsyncStreamInterface {
     @discardableResult
     func send(_ input: Input) throws -> Self {
@@ -102,4 +104,5 @@ extension BidirectionalAsyncStream: BidirectionalAsyncStreamInterface {
 }
 
 // Conforms to the client-only interface since it matches exactly and the implementation is internal
+@available(iOS 13, *)
 extension BidirectionalAsyncStream: ClientOnlyAsyncStreamInterface {}

Libraries/Connect/Implementation/Streaming/ServerOnlyAsyncStream.swift

@@ -15,6 +15,7 @@
 import SwiftProtobuf
 
 /// Concrete implementation of `ServerOnlyAsyncStreamInterface`.
+@available(iOS 13, *)
 final class ServerOnlyAsyncStream<Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message> {
     private let bidirectionalStream: BidirectionalAsyncStream<Input, Output>
 
@@ -23,6 +24,7 @@ final class ServerOnlyAsyncStream<Input: SwiftProtobuf.Message, Output: SwiftPro
     }
 }
 
+@available(iOS 13, *)
 extension ServerOnlyAsyncStream: ServerOnlyAsyncStreamInterface {
     func send(_ input: Input) throws {
         try self.bidirectionalStream.send(input)

Libraries/Connect/Implementation/UnaryAsyncWrapper.swift

@@ -20,6 +20,7 @@ import SwiftProtobuf
 /// For discussions on why this is necessary, see:
 /// https://forums.swift.org/t/how-to-use-withtaskcancellationhandler-properly/54341/37
 /// https://stackoverflow.com/q/71898080
+@available(iOS 13, *)
 actor UnaryAsyncWrapper<Output: SwiftProtobuf.Message> {
     private var cancelable: Cancelable?
     private let sendUnary: PerformClosure

Libraries/Connect/Interfaces/ProtocolClientInterface.swift

@@ -114,6 +114,7 @@ public protocol ProtocolClientInterface {
     /// - parameter headers: The outbound request headers to include.
     ///
     /// - returns: The response which is returned asynchronously.
+    @available(iOS 13, *)
     func unary<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(
@@ -134,6 +135,7 @@ public protocol ProtocolClientInterface {
     /// - parameter headers: The outbound request headers to include.
     ///
     /// - returns: An interface for sending and receiving data over the stream using async/await.
+    @available(iOS 13, *)
     func bidirectionalStream<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(
@@ -153,6 +155,7 @@ public protocol ProtocolClientInterface {
     /// - parameter headers: The outbound request headers to include.
     ///
     /// - returns: An interface for sending and receiving data over the stream using async/await.
+    @available(iOS 13, *)
     func clientOnlyStream<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(
@@ -172,6 +175,7 @@ public protocol ProtocolClientInterface {
     /// - parameter headers: The outbound request headers to include.
     ///
     /// - returns: An interface for sending and receiving data over the stream using async/await.
+    @available(iOS 13, *)
     func serverOnlyStream<
         Input: SwiftProtobuf.Message, Output: SwiftProtobuf.Message
     >(

Libraries/Connect/Interfaces/Streams/BidirectionalAsyncStreamInterface.swift

@@ -15,6 +15,7 @@
 import SwiftProtobuf
 
 /// Represents a bidirectional stream that can be interacted with using async/await.
+@available(iOS 13, *)
 public protocol BidirectionalAsyncStreamInterface<Input, Output> {
     /// The input (request) message type.
     associatedtype Input: SwiftProtobuf.Message

Libraries/Connect/Interfaces/Streams/ClientOnlyAsyncStreamInterface.swift

@@ -16,6 +16,7 @@ import SwiftProtobuf
 
 /// Represents a client-only stream (a stream where the client streams data to the server and
 /// eventually receives a response) that can be interacted with using async/await.
+@available(iOS 13, *)
 public protocol ClientOnlyAsyncStreamInterface<Input, Output> {
     /// The input (request) message type.
     associatedtype Input: SwiftProtobuf.Message

Libraries/Connect/Interfaces/Streams/ServerOnlyAsyncStreamInterface.swift

@@ -16,6 +16,7 @@ import SwiftProtobuf
 
 /// Represents a server-only stream (a stream where the server streams data to the client after
 /// receiving an initial request) that can be interacted with using async/await.
+@available(iOS 13, *)
 public protocol ServerOnlyAsyncStreamInterface<Input, Output> {
     /// The input (request) message type.
     associatedtype Input: SwiftProtobuf.Message

Package.swift

@@ -19,7 +19,7 @@ import PackageDescription
 let package = Package(
     name: "Connect",
     platforms: [
-        .iOS(.v14),
+        .iOS(.v12),
         .macOS(.v10_15),
     ],
     products: [

Plugins/ConnectMocksPlugin/ConnectMockGenerator.swift

@@ -82,6 +82,7 @@ final class ConnectMockGenerator: Generator {
                     self.printLine(
                         "/// Mocked for async calls to `\(method.name(using: self.options))()`."
                     )
+                    self.printLine("@available(iOS 13, *)")
                     self.printLine(
                         """
                         \(self.propertyVisibility) var \(method.asyncAwaitMockPropertyName()) = \
@@ -143,6 +144,7 @@ final class ConnectMockGenerator: Generator {
     private func printAsyncAwaitMethodMockImplementation(for method: MethodDescriptor) {
         self.printLine()
 
+        self.printLine("@available(iOS 13, *)")
         self.printLine(
             "\(self.typeVisibility) "
             + method.asyncAwaitSignature(

Plugins/ConnectSwiftPlugin/ConnectClientGenerator.swift

@@ -131,6 +131,7 @@ final class ConnectClientGenerator: Generator {
     private func printAsyncAwaitMethodInterface(for method: MethodDescriptor) {
         self.printLine()
         self.printCommentsIfNeeded(for: method)
+        self.printLine("@available(iOS 13, *)")
         self.printLine(
             method.asyncAwaitSignature(
                 using: self.namer, includeDefaults: false, options: self.options
@@ -159,6 +160,7 @@ final class ConnectClientGenerator: Generator {
 
     private func printAsyncAwaitMethodImplementation(for method: MethodDescriptor) {
         self.printLine()
+        self.printLine("@available(iOS 13, *)")
         self.printLine(
             "\(self.visibility) "
             + method.asyncAwaitSignature(