Swift 6 build fixes for Vertex AI (#14480)

Author: paulb777

FirebaseVertexAI/Sources/Protocols/Internal/CodableProtoEnum.swift

@@ -13,7 +13,7 @@
 // limitations under the License.
 
 /// A type that represents a Protocol Buffer raw enum value.
-protocol ProtoEnum {
+protocol ProtoEnum: Sendable {
   /// The type representing the valid values for the protobuf enum.
   ///
   /// > Important: This type must conform to `RawRepresentable` with the `RawValue == String`.

FirebaseVertexAI/Sources/Types/Public/Imagen/ImagenAspectRatio.swift

@@ -21,7 +21,7 @@ import Foundation
 /// documentation](https://cloud.google.com/vertex-ai/generative-ai/docs/image/generate-images#aspect-ratio)
 /// for more details and examples of the supported aspect ratios.
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-public struct ImagenAspectRatio {
+public struct ImagenAspectRatio: Sendable {
   /// Square (1:1) aspect ratio.
   ///
   /// Common uses for this aspect ratio include social media posts.

FirebaseVertexAI/Sources/Types/Public/Imagen/ImagenSafetyFilterLevel.swift

@@ -23,7 +23,7 @@
 /// guidelines](https://cloud.google.com/vertex-ai/generative-ai/docs/image/responsible-ai-imagen#safety-filters)
 /// for more details.
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-public struct ImagenSafetyFilterLevel: ProtoEnum {
+public struct ImagenSafetyFilterLevel: ProtoEnum, Sendable {
   enum Kind: String {
     case blockLowAndAbove = "block_low_and_above"
     case blockMediumAndAbove = "block_medium_and_above"

FirebaseVertexAI/Sources/Types/Public/Schema.swift

@@ -40,7 +40,7 @@ public class Schema {
 
   /// Modifiers describing the expected format of an integer `Schema`.
   @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-  public struct IntegerFormat: EncodableProtoEnum {
+  public struct IntegerFormat: EncodableProtoEnum, Sendable {
     enum Kind: String {
       case int32
       case int64

FirebaseVertexAI/Sources/VertexAI.swift

@@ -149,12 +149,21 @@ public class VertexAI {
 
   private let auth: AuthInterop?
 
-  /// A map of active  `VertexAI` instances keyed by the `FirebaseApp` name and the `location`, in
-  /// the format `appName:location`.
-  private static var instances: [String: VertexAI] = [:]
-
-  /// Lock to manage access to the `instances` array to avoid race conditions.
-  private static var instancesLock: os_unfair_lock = .init()
+  #if compiler(>=6)
+    /// A map of active  `VertexAI` instances keyed by the `FirebaseApp` name and the `location`, in
+    /// the format `appName:location`.
+    private nonisolated(unsafe) static var instances: [String: VertexAI] = [:]
+
+    /// Lock to manage access to the `instances` array to avoid race conditions.
+    private nonisolated(unsafe) static var instancesLock: os_unfair_lock = .init()
+  #else
+    /// A map of active  `VertexAI` instances keyed by the `FirebaseApp` name and the `location`, in
+    /// the format `appName:location`.
+    private static var instances: [String: VertexAI] = [:]
+
+    /// Lock to manage access to the `instances` array to avoid race conditions.
+    private static var instancesLock: os_unfair_lock = .init()
+  #endif
 
   let projectID: String
   let apiKey: String