[AI] Use common JSON encoder in LiveGenerativeModel (#7880)

Switched from the default `kotlinx.serialization.json.Json` encoder to
`com.google.firebase.ai.common.JSON` in `LiveGenerativeModel`. `JSON`
sets [`explicitNulls =
false`](https://github.com/firebase/firebase-android-sdk/blob/537bb20b6034d52515eb52fb3acb494326902356/ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/common/APIController.kt#L93),
which should prevent `parameters` and `parametersJsonSchema` from both
being specified (one as `null`) in the serialized JSON.

---------

Co-authored-by: Rodrigo Lazo Paz <rlazo@google.com>

Author: andrewheard

ai-logic/firebase-ai/CHANGELOG.md

@@ -1,5 +1,6 @@
 # Unreleased
 
+- [fixed] Fixed an issue causing Live API to fail when using the `GoogleAI` backend (#7880)
 - [changed] Added the `hybrid` component to request headers coming from `prefer_in_cloud` configurations (#7857)
 
 # 17.10.0

ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/GenerativeModel.kt

@@ -23,6 +23,7 @@ import android.net.NetworkCapabilities
 import com.google.firebase.FirebaseApp
 import com.google.firebase.ai.common.APIController
 import com.google.firebase.ai.common.AppCheckHeaderProvider
+import com.google.firebase.ai.common.JSON
 import com.google.firebase.ai.generativemodel.CloudGenerativeModelProvider
 import com.google.firebase.ai.generativemodel.FallbackGenerativeModelProvider
 import com.google.firebase.ai.generativemodel.GenerativeModelProvider
@@ -52,7 +53,6 @@ import com.google.firebase.appcheck.interop.InteropAppCheckTokenProvider
 import com.google.firebase.auth.internal.InternalAuthProvider
 import kotlinx.coroutines.flow.Flow
 import kotlinx.serialization.InternalSerializationApi
-import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.JsonPrimitive
 import kotlinx.serialization.json.jsonObject
@@ -272,7 +272,7 @@ internal constructor(
     parameter: String
   ): FunctionResponsePart {
     val inputDeserializer = functionDeclaration.inputSchema.getSerializer()
-    val input = Json.decodeFromString(inputDeserializer, parameter)
+    val input = JSON.decodeFromString(inputDeserializer, parameter)
     val functionReference =
       functionDeclaration.functionReference
         ?: throw RuntimeException("Function reference for ${functionDeclaration.name} is missing")
@@ -281,7 +281,7 @@ internal constructor(
       val outputSerializer = functionDeclaration.outputSchema?.getSerializer()
       if (outputSerializer != null) {
         return FunctionResponsePart.from(
-            Json.encodeToJsonElement(outputSerializer, output).jsonObject
+            JSON.encodeToJsonElement(outputSerializer, output).jsonObject
           )
           .normalizeAgainstCall(functionCall)
       }

ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/LiveGenerativeModel.kt

@@ -40,7 +40,6 @@ import kotlin.coroutines.CoroutineContext
 import kotlinx.coroutines.channels.ClosedReceiveChannelException
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.encodeToString
-import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonObject
 
 /**
@@ -116,7 +115,7 @@ internal constructor(
           config?.outputAudioTranscription?.toInternal()
         )
         .toInternal()
-    val data: String = Json.encodeToString(clientMessage)
+    val data: String = JSON.encodeToString(clientMessage)
     var webSession: DefaultClientWebSocketSession? = null
     try {
       webSession = controller.getWebSocketSession(location)

ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/TemplateImagenModel.kt

@@ -19,6 +19,7 @@ package com.google.firebase.ai
 import com.google.firebase.FirebaseApp
 import com.google.firebase.ai.common.APIController
 import com.google.firebase.ai.common.AppCheckHeaderProvider
+import com.google.firebase.ai.common.JSON
 import com.google.firebase.ai.common.TemplateGenerateImageRequest
 import com.google.firebase.ai.type.FirebaseAIException
 import com.google.firebase.ai.type.ImagenGenerationResponse
@@ -27,7 +28,6 @@ import com.google.firebase.ai.type.PublicPreviewAPI
 import com.google.firebase.ai.type.RequestOptions
 import com.google.firebase.appcheck.interop.InteropAppCheckTokenProvider
 import com.google.firebase.auth.internal.InternalAuthProvider
-import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.jsonObject
 import org.json.JSONObject
 
@@ -96,7 +96,7 @@ internal constructor(
     inputs: Map<String, Any>
   ): TemplateGenerateImageRequest {
     return TemplateGenerateImageRequest(
-      Json.parseToJsonElement(JSONObject(inputs).toString()).jsonObject
+      JSON.parseToJsonElement(JSONObject(inputs).toString()).jsonObject
     )
   }
 

ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/LiveSession.kt

@@ -63,7 +63,6 @@ import kotlinx.coroutines.launch
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.encodeToString
-import kotlinx.serialization.json.Json
 
 /** Represents a live WebSocket session capable of streaming content to and from the server. */
 @PublicPreviewAPI
@@ -372,14 +371,10 @@ internal constructor(
    * response from the client.
    */
   public suspend fun sendFunctionResponse(functionList: List<FunctionResponsePart>) {
-    FirebaseAIException.catchAsync {
-      val jsonString =
-        Json.encodeToString(
-          BidiGenerateContentToolResponseSetup(functionList.map { it.toInternalFunctionResponse() })
-            .toInternal()
-        )
-      session.send(Frame.Text(jsonString))
-    }
+    sendFrame(
+      BidiGenerateContentToolResponseSetup(functionList.map { it.toInternalFunctionResponse() })
+        .toInternal()
+    )
   }
 
   /**
@@ -393,11 +388,7 @@ internal constructor(
    * results, send 16-bit PCM audio at 24kHz.
    */
   public suspend fun sendAudioRealtime(audio: InlineData) {
-    FirebaseAIException.catchAsync {
-      val jsonString =
-        Json.encodeToString(BidiGenerateContentRealtimeInputSetup(audio = audio).toInternal())
-      session.send(Frame.Text(jsonString))
-    }
+    sendFrame(BidiGenerateContentRealtimeInputSetup(audio = audio).toInternal())
   }
 
   /**
@@ -415,11 +406,7 @@ internal constructor(
    * data (for example, `image/png`, `image/jpeg`, etc.).
    */
   public suspend fun sendVideoRealtime(video: InlineData) {
-    FirebaseAIException.catchAsync {
-      val jsonString =
-        Json.encodeToString(BidiGenerateContentRealtimeInputSetup(video = video).toInternal())
-      session.send(Frame.Text(jsonString))
-    }
+    sendFrame(BidiGenerateContentRealtimeInputSetup(video = video).toInternal())
   }
 
   /**
@@ -428,11 +415,7 @@ internal constructor(
    * @param text Text content to append to the current client's conversation.
    */
   public suspend fun sendTextRealtime(text: String) {
-    FirebaseAIException.catchAsync {
-      val jsonString =
-        Json.encodeToString(BidiGenerateContentRealtimeInputSetup(text = text).toInternal())
-      session.send(Frame.Text(jsonString))
-    }
+    sendFrame(BidiGenerateContentRealtimeInputSetup(text = text).toInternal())
   }
 
   /**
@@ -446,16 +429,10 @@ internal constructor(
   public suspend fun sendMediaStream(
     mediaChunks: List<MediaData>,
   ) {
-    FirebaseAIException.catchAsync {
-      val jsonString =
-        Json.encodeToString(
-          BidiGenerateContentRealtimeInputSetup(
-              mediaChunks.map { InlineData(it.data, it.mimeType) }
-            )
-            .toInternal()
-        )
-      session.send(Frame.Text(jsonString))
-    }
+    sendFrame(
+      BidiGenerateContentRealtimeInputSetup(mediaChunks.map { InlineData(it.data, it.mimeType) })
+        .toInternal()
+    )
   }
 
   /**
@@ -466,14 +443,24 @@ internal constructor(
    * @param content Client [Content] to be sent to the model.
    */
   public suspend fun send(content: Content) {
+    sendFrame(
+      BidiGenerateContentClientContentSetup(listOf(content.toInternal()), true).toInternal()
+    )
+  }
+
+  /**
+   * Encodes the provided data to a JSON string and sends it over the WebSocket session.
+   *
+   * If an exception is thrown, it will be handled by [FirebaseAIException.catchAsync]
+   *
+   * @param T The type of the data to be sent, which must be serializable.
+   * @param data The data object to be encoded and sent.
+   */
+  private suspend inline fun <reified T> sendFrame(data: T) =
     FirebaseAIException.catchAsync {
-      val jsonString =
-        Json.encodeToString(
-          BidiGenerateContentClientContentSetup(listOf(content.toInternal()), true).toInternal()
-        )
+      val jsonString = JSON.encodeToString(data)
       session.send(Frame.Text(jsonString))
     }
-  }
 
   /**
    * Sends text to the model.

ai-logic/firebase-ai/src/test/java/com/google/firebase/ai/type/ThinkingConfigTest.kt

@@ -16,10 +16,10 @@
 
 package com.google.firebase.ai.type
 
+import com.google.firebase.ai.common.JSON
 import io.kotest.assertions.json.shouldEqualJson
 import io.kotest.matchers.equals.shouldBeEqual
 import kotlinx.serialization.encodeToString
-import kotlinx.serialization.json.Json
 import org.junit.Test
 
 internal class ThinkingConfigTest {
@@ -36,7 +36,7 @@ internal class ThinkingConfigTest {
       """
         .trimIndent()
 
-    Json.encodeToString(thinkingConfig.toInternal()).shouldEqualJson(expectedJson)
+    JSON.encodeToString(thinkingConfig.toInternal()).shouldEqualJson(expectedJson)
   }
 
   @Test
@@ -51,7 +51,7 @@ internal class ThinkingConfigTest {
       """
         .trimIndent()
 
-    Json.encodeToString(thinkingConfig.toInternal()).shouldEqualJson(expectedJson)
+    JSON.encodeToString(thinkingConfig.toInternal()).shouldEqualJson(expectedJson)
   }
 
   @Test