[Vertex AI] Add responseMIMEType to GenerationConfig (#12918)

FirebaseVertexAI/Sources/GenerationConfig.swift

@@ -63,6 +63,13 @@ public struct GenerationConfig {
   /// The stop sequence will not be included as part of the response.
   public let stopSequences: [String]?
 
+  /// Output response MIME type of the generated candidate text.
+  ///
+  /// Supported MIME types:
+  /// - `text/plain`: Text output; the default behavior if unspecified.
+  /// - `application/json`: JSON response in the candidates.
+  public let responseMIMEType: String?
+
   /// Creates a new `GenerationConfig` value.
   ///
   /// - Parameter temperature: See ``temperature``
@@ -73,7 +80,7 @@ public struct GenerationConfig {
   /// - Parameter stopSequences: See ``stopSequences``
   public init(temperature: Float? = nil, topP: Float? = nil, topK: Int? = nil,
               candidateCount: Int? = nil, maxOutputTokens: Int? = nil,
-              stopSequences: [String]? = nil) {
+              stopSequences: [String]? = nil, responseMIMEType: String? = nil) {
     // Explicit init because otherwise if we re-arrange the above variables it changes the API
     // surface.
     self.temperature = temperature
@@ -82,6 +89,7 @@ public struct GenerationConfig {
     self.candidateCount = candidateCount
     self.maxOutputTokens = maxOutputTokens
     self.stopSequences = stopSequences
+    self.responseMIMEType = responseMIMEType
   }
 }
 

FirebaseVertexAI/Tests/Unit/GenerationConfigTests.swift

@@ -0,0 +1,94 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import FirebaseVertexAI
+import Foundation
+import XCTest
+
+@available(iOS 15.0, macOS 11.0, macCatalyst 15.0, *)
+final class GenerationConfigTests: XCTestCase {
+  let encoder = JSONEncoder()
+
+  override func setUp() {
+    encoder.outputFormatting = .init(
+      arrayLiteral: .prettyPrinted, .sortedKeys, .withoutEscapingSlashes
+    )
+  }
+
+  // MARK: GenerationConfig Encoding
+
+  func testEncodeGenerationConfig_default() throws {
+    let generationConfig = GenerationConfig()
+
+    let jsonData = try encoder.encode(generationConfig)
+
+    let json = try XCTUnwrap(String(data: jsonData, encoding: .utf8))
+    XCTAssertEqual(json, """
+    {
+
+    }
+    """)
+  }
+
+  func testEncodeGenerationConfig_allOptions() throws {
+    let temperature: Float = 0.5
+    let topP: Float = 0.75
+    let topK = 40
+    let candidateCount = 2
+    let maxOutputTokens = 256
+    let stopSequences = ["END", "DONE"]
+    let responseMIMEType = "text/plain"
+    let generationConfig = GenerationConfig(
+      temperature: temperature,
+      topP: topP,
+      topK: topK,
+      candidateCount: candidateCount,
+      maxOutputTokens: maxOutputTokens,
+      stopSequences: stopSequences,
+      responseMIMEType: responseMIMEType
+    )
+
+    let jsonData = try encoder.encode(generationConfig)
+
+    let json = try XCTUnwrap(String(data: jsonData, encoding: .utf8))
+    XCTAssertEqual(json, """
+    {
+      "candidateCount" : \(candidateCount),
+      "maxOutputTokens" : \(maxOutputTokens),
+      "responseMIMEType" : "\(responseMIMEType)",
+      "stopSequences" : [
+        "END",
+        "DONE"
+      ],
+      "temperature" : \(temperature),
+      "topK" : \(topK),
+      "topP" : \(topP)
+    }
+    """)
+  }
+
+  func testEncodeGenerationConfig_responseMIMEType() throws {
+    let mimeType = "image/jpeg"
+    let generationConfig = GenerationConfig(responseMIMEType: mimeType)
+
+    let jsonData = try encoder.encode(generationConfig)
+
+    let json = try XCTUnwrap(String(data: jsonData, encoding: .utf8))
+    XCTAssertEqual(json, """
+    {
+      "responseMIMEType" : "\(mimeType)"
+    }
+    """)
+  }
+}

FirebaseVertexAI/Tests/Unit/VertexAIAPITests.swift

@@ -30,7 +30,8 @@ final class VertexAIAPITests: XCTestCase {
                                   topK: 16,
                                   candidateCount: 4,
                                   maxOutputTokens: 256,
-                                  stopSequences: ["..."])
+                                  stopSequences: ["..."],
+                                  responseMIMEType: "text/plain")
     let filters = [SafetySetting(harmCategory: .dangerousContent, threshold: .blockOnlyHigh)]
     let systemInstruction = ModelContent(role: "system", parts: [.text("Talk like a pirate.")])