[AI] Nullable support in structured output and more integration tests (#15752)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Andrew Heard <andrewheard@google.com>

Author: 3 people

FirebaseAI/Sources/Protocols/Public/StructuredOutput/FirebaseGenerable.swift

@@ -40,6 +40,17 @@ extension Optional: ConvertibleToModelOutput where Wrapped: ConvertibleToModelOu
   }
 }
 
+@available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
+extension Optional: ConvertibleFromModelOutput where Wrapped: ConvertibleFromModelOutput {
+  public init(_ content: ModelOutput) throws {
+    if case .null = content.kind {
+      self = nil
+      return
+    }
+    self = try Wrapped(content)
+  }
+}
+
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 extension Bool: FirebaseGenerable {
   public static var jsonSchema: JSONSchema {

FirebaseAI/Sources/Types/Public/StructuredOutput/ModelOutput.swift

@@ -120,6 +120,10 @@ public struct ModelOutput: Sendable, CustomDebugStringConvertible, FirebaseGener
       return nil
     }
 
+    if case .null = value.kind {
+      return nil
+    }
+
     return try Value(value)
   }
 }

FirebaseAI/Tests/TestApp/Packages/FirebaseAILogicExtended/Tests/FirebaseGenerableMacroTests/FirebaseGenerableTests.swift

@@ -36,13 +36,15 @@ final class FirebaseAILogicMacrosTests: XCTestCase {
         @FirebaseGenerable
         struct Person {
           let firstName: String
+          let middleName: String?
           let lastName: String
           let age: Int
         }
         """,
         expandedSource: """
         struct Person {
           let firstName: String
+          let middleName: String?
           let lastName: String
           let age: Int
 
@@ -51,6 +53,7 @@ final class FirebaseAILogicMacrosTests: XCTestCase {
                 type: Self.self,
                 properties: [
                     FirebaseAILogic.JSONSchema.Property(name: "firstName", type: String.self),
+                    FirebaseAILogic.JSONSchema.Property(name: "middleName", type: String?.self),
                     FirebaseAILogic.JSONSchema.Property(name: "lastName", type: String.self),
                     FirebaseAILogic.JSONSchema.Property(name: "age", type: Int.self)
                 ]
@@ -60,6 +63,7 @@ final class FirebaseAILogicMacrosTests: XCTestCase {
             nonisolated var modelOutput: FirebaseAILogic.ModelOutput {
               var properties = [(name: String, value: any ConvertibleToModelOutput)]()
               addProperty(name: "firstName", value: self.firstName)
+              addProperty(name: "middleName", value: self.middleName)
               addProperty(name: "lastName", value: self.lastName)
               addProperty(name: "age", value: self.age)
               return ModelOutput(
@@ -81,11 +85,13 @@ final class FirebaseAILogicMacrosTests: XCTestCase {
             nonisolated struct Partial: Identifiable, FirebaseAILogic.ConvertibleFromModelOutput {
               var id: FirebaseAILogic.ResponseID
               var firstName: String.Partial?
+              var middleName: String?.Partial?
               var lastName: String.Partial?
               var age: Int.Partial?
               nonisolated init(_ content: FirebaseAILogic.ModelOutput) throws {
                 self.id = content.id ?? FirebaseAILogic.ResponseID()
                 self.firstName = try content.value(forProperty: "firstName")
+                self.middleName = try content.value(forProperty: "middleName")
                 self.lastName = try content.value(forProperty: "lastName")
                 self.age = try content.value(forProperty: "age")
               }
@@ -96,6 +102,7 @@ final class FirebaseAILogicMacrosTests: XCTestCase {
         extension Person: FirebaseAILogic.FirebaseGenerable {
           nonisolated init(_ content: FirebaseAILogic.ModelOutput) throws {
             self.firstName = try content.value(forProperty: "firstName")
+            self.middleName = try content.value(forProperty: "middleName")
             self.lastName = try content.value(forProperty: "lastName")
             self.age = try content.value(forProperty: "age")
           }