Move availability inline (#105)

Motivation:

It's hard for packages to incrementally adopt gRPC with platforms in the
package manifest as it requires packages to include platforms in their
manifest or mint a new major version.

Modifications:

- Move platform availability onto source code
- Check annotations in CI

Result:

Easier to adopt

Author: glbrntt

.github/workflows/main.yml

@@ -13,10 +13,10 @@ jobs:
     with:
       linux_5_9_enabled: false
       linux_5_10_enabled: false
-      linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-      linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-      linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-      linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
+      linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
+      linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
+      linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
+      linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
 
   construct-integration-tests-matrix:
     name: Construct integration matrix

.github/workflows/pull_request.yml

@@ -22,10 +22,10 @@ jobs:
     with:
       linux_5_9_enabled: false
       linux_5_10_enabled: false
-      linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-      linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-      linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
-      linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
+      linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
+      linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
+      linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
+      linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors -Xswiftc -require-explicit-availability"
 
   construct-integration-tests-matrix:
     name: Construct integration matrix

Package.swift

@@ -35,7 +35,7 @@ let products: [Product] = [
 let dependencies: [Package.Dependency] = [
   .package(
     url: "https://github.com/grpc/grpc-swift.git",
-    from: "2.2.0"
+    from: "2.2.1"
   ),
   .package(
     url: "https://github.com/apple/swift-nio.git",
@@ -67,12 +67,28 @@ let dependencies: [Package.Dependency] = [
   ),
 ]
 
-let defaultSwiftSettings: [SwiftSetting] = [
-  .swiftLanguageMode(.v6),
-  .enableUpcomingFeature("ExistentialAny"),
-  .enableUpcomingFeature("InternalImportsByDefault"),
-  .enableUpcomingFeature("MemberImportVisibility"),
-]
+// -------------------------------------------------------------------------------------------------
+
+// This adds some build settings which allow us to map "@available(gRPCSwiftNIOTransport 1.x, *)" to
+// the appropriate OS platforms.
+let nextMinorVersion = 3
+let availabilitySettings: [SwiftSetting] = (0 ... nextMinorVersion).map { minor in
+  let name = "gRPCSwiftNIOTransport"
+  let version = "1.\(minor)"
+  let platforms = "macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0"
+  let setting = "AvailabilityMacro=\(name) \(version):\(platforms)"
+  return .enableExperimentalFeature(setting)
+}
+
+let defaultSwiftSettings: [SwiftSetting] =
+  availabilitySettings + [
+    .swiftLanguageMode(.v6),
+    .enableUpcomingFeature("ExistentialAny"),
+    .enableUpcomingFeature("InternalImportsByDefault"),
+    .enableUpcomingFeature("MemberImportVisibility"),
+  ]
+
+// -------------------------------------------------------------------------------------------------
 
 let targets: [Target] = [
   // C-module for z-lib shims
@@ -156,13 +172,6 @@ let targets: [Target] = [
 
 let package = Package(
   name: "grpc-swift-nio-transport",
-  platforms: [
-    .macOS(.v15),
-    .iOS(.v18),
-    .tvOS(.v18),
-    .watchOS(.v11),
-    .visionOS(.v2),
-  ],
   products: products,
   dependencies: dependencies,
   targets: targets

Sources/GRPCNIOTransportCore/Client/Connection/Connection.swift

@@ -43,6 +43,7 @@ private import Synchronization
 ///   }
 /// }
 /// ```
+@available(gRPCSwiftNIOTransport 1.0, *)
 package final class Connection: Sendable {
   /// Events which can happen over the lifetime of the connection.
   package enum Event: Sendable {
@@ -405,6 +406,7 @@ package final class Connection: Sendable {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension Connection {
   package struct Stream {
     package typealias Inbound = NIOAsyncChannelInboundStream<RPCResponsePart<GRPCNIOTransportBytes>>
@@ -478,6 +480,7 @@ extension Connection {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension Connection {
   private enum State: Sendable {
     /// The connection is idle or connecting.

Sources/GRPCNIOTransportCore/Client/Connection/ConnectionBackoff.swift

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 package struct ConnectionBackoff {
   package var initial: Duration
   package var max: Duration

Sources/GRPCNIOTransportCore/Client/Connection/ConnectionFactory.swift

@@ -18,6 +18,7 @@ package import NIOCore
 package import NIOHTTP2
 internal import NIOPosix
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 package protocol HTTP2Connector: Sendable {
   /// Attempt to establish a connection to the given address.
   ///
@@ -30,6 +31,7 @@ package protocol HTTP2Connector: Sendable {
   ) async throws -> HTTP2Connection
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 package struct HTTP2Connection: Sendable {
   /// The underlying TCP connection wrapped up for use with gRPC.
   var channel: NIOAsyncChannel<ClientConnectionEvent, Void>

Sources/GRPCNIOTransportCore/Client/Connection/ConnectivityState.swift

@@ -16,6 +16,7 @@
 
 package import GRPCCore
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 package enum ConnectivityState: Sendable, Hashable {
   /// This channel isn't trying to create a connection because of a lack of new or pending RPCs.
   ///

Sources/GRPCNIOTransportCore/Client/Connection/GRPCChannel.swift

@@ -18,6 +18,7 @@ private import DequeModule
 package import GRPCCore
 private import Synchronization
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 package final class GRPCChannel: ClientTransport {
   package typealias Bytes = GRPCNIOTransportBytes
 
@@ -239,6 +240,7 @@ package final class GRPCChannel: ClientTransport {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension GRPCChannel {
   package struct Config: Sendable {
     /// Configuration for HTTP/2 connections.
@@ -267,6 +269,7 @@ extension GRPCChannel {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension GRPCChannel {
   enum MakeStreamResult {
     /// A stream was created, use it.
@@ -365,6 +368,7 @@ extension GRPCChannel {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension GRPCChannel {
   private func handleClose(in group: inout DiscardingTaskGroup) {
     switch self.state.withLock({ $0.close() }) {
@@ -593,6 +597,7 @@ extension GRPCChannel {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension GRPCChannel {
   struct StateMachine {
     enum State {
@@ -667,6 +672,7 @@ extension GRPCChannel {
   }
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension GRPCChannel.StateMachine {
   mutating func start() {
     precondition(!self.running, "channel must only be started once")

Sources/GRPCNIOTransportCore/Client/Connection/LoadBalancers/LoadBalancer.swift

@@ -14,11 +14,13 @@
  * limitations under the License.
  */
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 package enum LoadBalancer: Sendable {
   case roundRobin(RoundRobinLoadBalancer)
   case pickFirst(PickFirstLoadBalancer)
 }
 
+@available(gRPCSwiftNIOTransport 1.0, *)
 extension LoadBalancer {
   package init(_ loadBalancer: RoundRobinLoadBalancer) {
     self = .roundRobin(loadBalancer)

Sources/GRPCNIOTransportCore/Client/Connection/LoadBalancers/LoadBalancerEvent.swift

@@ -15,6 +15,7 @@
  */
 
 /// Events emitted by load-balancers.
+@available(gRPCSwiftNIOTransport 1.0, *)
 package enum LoadBalancerEvent: Sendable, Hashable {
   /// The connectivity state of the subchannel changed.
   case connectivityStateChanged(ConnectivityState)