Fix Concurrency Warnings in Swift 6 (#310)

Co-authored-by: Vera Xia <zhvxia@amazon.com>

Author: waahm7

.github/workflows/ci.yml

@@ -71,6 +71,35 @@ jobs:
         chmod a+x builder
         ./builder build -p ${{ env.PACKAGE_NAME }}
 
+  # Test that everything works with Swift 6 strict concurrency. We can remove this CI in the future once we raise our minimum Swift version to Swift 6.
+  macos-swift6:
+    runs-on: macos-15
+    env:
+      DEVELOPER_DIR: /Applications/Xcode.app
+      XCODE_DESTINATION: 'OS X'
+      NSUnbufferedIO: YES
+    strategy:
+      fail-fast: false
+    steps:
+    - uses: aws-actions/configure-aws-credentials@v4
+      with:
+        role-to-assume: ${{ env.CRT_CI_ROLE }}
+        aws-region: ${{ env.AWS_DEFAULT_REGION }} 
+    - name: Checkout repository
+      uses: actions/checkout@v4
+      with:
+        submodules: true
+        fetch-depth: 0
+    - name: Set Swift version to 6
+      run: |
+        sed -i '' 's/swift-tools-version:5\.[0-9][0-9]*/swift-tools-version:6\.0/' Package.swift
+        # Verify that substitution was successful 
+        grep -q 'swift-tools-version:6\.0' Package.swift || (echo "No version 5.x found to update" && exit 1)
+    - name: Build ${{ env.PACKAGE_NAME }} + consumers
+      run: |
+        swift build
+        swift test
+
   devices:
     runs-on: ${{ matrix.runner }}
     env:

Package.swift

@@ -11,6 +11,10 @@ var package = Package(name: "aws-crt-swift",
                       products: [
                         .library(name: "AwsCommonRuntimeKit", targets: ["AwsCommonRuntimeKit"]),
                         .executable(name: "Elasticurl", targets: ["Elasticurl"])
+                      ],
+                      dependencies: [
+                        // Arugment Parser Dependency for ElasticCurl
+                        .package(url: "https://github.com/apple/swift-argument-parser.git", .upToNextMajor(from: "1.5.0"))
                       ]
 )
 
@@ -332,7 +336,10 @@ packageTargets.append(contentsOf: [
     ),
     .executableTarget(
         name: "Elasticurl",
-        dependencies: ["AwsCommonRuntimeKit"],
+        dependencies: [
+            "AwsCommonRuntimeKit",
+            .product(name: "ArgumentParser", package: "swift-argument-parser"),
+        ],
         path: "Source/Elasticurl"
     )
 ] )

Source/AwsCommonRuntimeKit/CommonRuntimeKit.swift

@@ -1,12 +1,10 @@
-import AwsCEventStream
 import AwsCAuth
+import AwsCEventStream
 import AwsCMqtt
 import LibNative
 
-/**
- * Initializes the library.
- * `CommonRuntimeKit.initialize` must be called before using any other functionality.
- */
+/// Initializes the library.
+/// `CommonRuntimeKit.initialize` must be called before using any other functionality.
 public struct CommonRuntimeKit {
 
     /// Initializes the library.
@@ -15,20 +13,23 @@ public struct CommonRuntimeKit {
         aws_auth_library_init(allocator.rawValue)
         aws_event_stream_library_init(allocator.rawValue)
         aws_mqtt_library_init(allocator.rawValue)
-        aws_register_error_info(&s_crt_swift_error_list)
+        withUnsafePointer(to: s_crt_swift_error_list) { ptr in
+            aws_register_error_info(ptr)
+        }
     }
 
     /**
      * This is an optional cleanup function which will block until all the CRT resources have cleaned up.
      * Use this function only if you want to make sure that there are no memory leaks at the end of the application.
      * Warning: It will hang if you are still holding references to any CRT objects such as HostResolver.
      */
-    public static func cleanUp() {
-        aws_unregister_error_info(&s_crt_swift_error_list)
+    public static nonisolated func cleanUp() {
+        withUnsafePointer(to: s_crt_swift_error_list) { ptr in
+            aws_unregister_error_info(ptr)
+        }
         aws_mqtt_library_clean_up()
         aws_event_stream_library_clean_up()
         aws_auth_library_clean_up()
-
     }
 
     private init() {}

Source/AwsCommonRuntimeKit/auth/credentials/Credentials.swift

@@ -4,7 +4,9 @@
 import AwsCAuth
 import Foundation
 
-public final class Credentials {
+// We can't mutate this class after initialization. Swift can not verify the sendability due to OpaquePointer,
+// So mark it unchecked Sendable
+public final class Credentials: @unchecked Sendable {
 
     let rawValue: OpaquePointer
 

Source/AwsCommonRuntimeKit/auth/credentials/CredentialsProvider.swift

@@ -34,8 +34,9 @@ public struct CognitoLoginPair: CStruct {
     }
 }
 
-public class CredentialsProvider: CredentialsProviding {
-
+// We can't mutate this class after initialization. Swift can not verify the sendability due to pointer,
+// So mark it unchecked Sendable
+public class CredentialsProvider: CredentialsProviding, @unchecked Sendable {
     let rawValue: UnsafeMutablePointer<aws_credentials_provider>
 
     init(credentialsProvider: UnsafeMutablePointer<aws_credentials_provider>) {
@@ -667,25 +668,19 @@ private func onGetCredentials(credentials: OpaquePointer?,
     continuationCore.continuation.resume(returning: Credentials(rawValue: credentials!))
 }
 
-// We need to share this pointer to C in a task block but Swift compiler complains
-// that Pointer does not conform to Sendable. Wrap the pointer in a @unchecked Sendable block
-// for Swift compiler to stop complaining.
-struct SendablePointer: @unchecked Sendable {
-    let pointer: UnsafeMutableRawPointer
-}
-
 private func getCredentialsDelegateFn(_ delegatePtr: UnsafeMutableRawPointer!,
                                       _ callbackFn: (@convention(c) (
                                                         OpaquePointer?,
                                                         Int32,
                                                         UnsafeMutableRawPointer?) -> Void)!,
                                       _ userData: UnsafeMutableRawPointer!) -> Int32 {
-    let delegate = Unmanaged<Box<CredentialsProviding>>
-        .fromOpaque(delegatePtr)
-        .takeUnretainedValue().contents
-    let userData = SendablePointer(pointer: userData)
+    let userData = SendableRawPointer(pointer: userData)
+    let delegatePtr = SendableRawPointer(pointer: delegatePtr)
     Task {
         do {
+            let delegate = Unmanaged<Box<CredentialsProviding>>
+                .fromOpaque(delegatePtr.pointer!)
+                .takeUnretainedValue().contents
             let credentials = try await delegate.getCredentials()
             callbackFn(credentials.rawValue, AWS_OP_SUCCESS, userData.pointer)
         } catch CommonRunTimeError.crtError(let crtError) {

Source/AwsCommonRuntimeKit/auth/imds/IAMProfile.swift

@@ -4,7 +4,7 @@
 import AwsCAuth
 import Foundation
 
-public struct IAMProfile {
+public struct IAMProfile: @unchecked Sendable {
     public let lastUpdated: Date
     public let profileArn: String
     public let profileId: String

Source/AwsCommonRuntimeKit/auth/imds/IMDSClient.swift

@@ -4,7 +4,9 @@
 import AwsCAuth
 
 // swiftlint:disable type_body_length
-public class IMDSClient {
+// We can't mutate this class after initialization. Swift can not verify the sendability due to OpaquePointer,
+// So mark it unchecked Sendable
+public class IMDSClient: @unchecked Sendable {
     let rawValue: OpaquePointer
 
     /// Creates an IMDSClient that always uses IMDSv2

Source/AwsCommonRuntimeKit/auth/imds/IMDSInstanceInfo.swift

@@ -4,7 +4,7 @@
 import AwsCAuth
 import Foundation
 
-public struct IMDSInstanceInfo {
+public struct IMDSInstanceInfo: @unchecked Sendable {
     public let marketPlaceProductCodes: [String]
     public let availabilityZone: String
     public let privateIp: String
@@ -21,7 +21,8 @@ public struct IMDSInstanceInfo {
     public let region: String
 
     init(instanceInfo: aws_imds_instance_info) {
-        self.marketPlaceProductCodes = instanceInfo.marketplace_product_codes.byteCursorListToStringArray()
+        self.marketPlaceProductCodes = instanceInfo.marketplace_product_codes
+            .byteCursorListToStringArray()
         self.availabilityZone = instanceInfo.availability_zone.toString()
         self.privateIp = instanceInfo.private_ip.toString()
         self.version = instanceInfo.version.toString()

Source/AwsCommonRuntimeKit/auth/signing/Signer.swift

@@ -164,9 +164,11 @@ public class Signer {
     }
 }
 
-class SignRequestCore {
+// After signing, we mutate the request and resume the continuation, which may result in a thread change.
+// We won't modify it after continuation.resume is called. So we can mark it @unchecked Sendable
+class SignRequestCore: @unchecked Sendable {
     let request: HTTPRequestBase
-    var continuation: CheckedContinuation<HTTPRequestBase, Error>
+    let continuation: CheckedContinuation<HTTPRequestBase, Error>
     let shouldSignHeader: ((String) -> Bool)?
     init(request: HTTPRequestBase,
          continuation: CheckedContinuation<HTTPRequestBase, Error>,
@@ -207,6 +209,7 @@ private func onRequestSigningComplete(signingResult: UnsafeMutablePointer<aws_si
     } else {
         signRequestCore.continuation.resume(throwing: CommonRunTimeError.crtError(.makeFromLastError()))
     }
+    // It's not thread-safe to modify `signingRequestCore.request` after continuation.resume
 }
 
 private func onSigningComplete(signingResult: UnsafeMutablePointer<aws_signing_result>?,
@@ -220,9 +223,10 @@ private func onSigningComplete(signingResult: UnsafeMutablePointer<aws_signing_r
 
     // Success
     var awsStringPointer: UnsafeMutablePointer<aws_string>!
+    let signature = AWSString("signature")
     guard aws_signing_result_get_property(
             signingResult!,
-            g_aws_signature_property_name,
+            signature.rawValue,
             &awsStringPointer) == AWS_OP_SUCCESS else {
         chunkSignerCore.continuation.resume(throwing: CommonRunTimeError.crtError(.makeFromLastError()))
         return

Source/AwsCommonRuntimeKit/auth/signing/SigningConfig.swift

@@ -4,7 +4,7 @@
 import AwsCAuth
 import Foundation
 
-public struct SigningConfig: CStructWithUserData {
+public struct SigningConfig: CStructWithUserData, @unchecked Sendable {
 
     /// What signing algorithm to use.
     public var algorithm: SigningAlgorithmType
@@ -136,7 +136,7 @@ private func onShouldSignHeader(nameCursor: UnsafePointer<aws_byte_cursor>!,
     return signRequestCore.shouldSignHeader!(name)
 }
 
-public enum SignatureType {
+public enum SignatureType: Sendable {
 
     /// A signature for a full http request should be computed, with header updates applied to the signing result.
     case requestHeaders
@@ -162,7 +162,7 @@ public enum SignatureType {
     case requestEvent
 }
 
-public enum SignedBodyHeaderType {
+public enum SignedBodyHeaderType: Sendable {
 
     /// Do not add a header
     case none
@@ -174,7 +174,7 @@ public enum SignedBodyHeaderType {
 /// Optional string to use as the canonical request's body value.
 /// Typically, this is the SHA-256 of the (request/chunk/event) payload, written as lowercase hex.
 /// If this has been precalculated, it can be set here. Special values used by certain services can also be set.
-public enum SignedBodyValue: CustomStringConvertible, Equatable {
+public enum SignedBodyValue: CustomStringConvertible, Equatable, Sendable {
     /// if empty, a public value  will be calculated from the payload during signing
     case empty
     /// For empty sha256
@@ -226,7 +226,7 @@ public enum SignedBodyValue: CustomStringConvertible, Equatable {
     }
 }
 
-public enum SigningAlgorithmType {
+public enum SigningAlgorithmType: Sendable {
     case signingV4
     case signingV4Asymmetric
     case signingV4S3Express