fix: Make FunctionResponses respect the order of FunctionCalls

PiperOrigin-RevId: 845729296

Author: google-genai-bot

core/src/main/java/com/google/adk/flows/llmflows/Functions.java

@@ -47,7 +47,6 @@
 import io.reactivex.rxjava3.core.Maybe;
 import io.reactivex.rxjava3.core.Single;
 import io.reactivex.rxjava3.disposables.Disposable;
-import io.reactivex.rxjava3.functions.Function;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -57,6 +56,7 @@
 import java.util.Optional;
 import java.util.Set;
 import java.util.UUID;
+import java.util.function.Function;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -202,10 +202,12 @@ public static Maybe<Event> handleFunctionCalls(
     Flowable<Event> functionResponseEventsFlowable;
     if (invocationContext.runConfig().toolExecutionMode() == ToolExecutionMode.SEQUENTIAL) {
       functionResponseEventsFlowable =
-          Flowable.fromIterable(functionCalls).concatMapMaybe(functionCallMapper);
+          Flowable.fromIterable(functionCalls)
+              .concatMapMaybe(call -> functionCallMapper.apply(call));
     } else {
       functionResponseEventsFlowable =
-          Flowable.fromIterable(functionCalls).flatMapMaybe(functionCallMapper);
+          Flowable.fromIterable(functionCalls)
+              .concatMapEager(call -> functionCallMapper.apply(call).toFlowable());
     }
     return functionResponseEventsFlowable
         .toList()
@@ -314,11 +316,12 @@ public static Maybe<Event> handleFunctionCallsLive(
 
     if (invocationContext.runConfig().toolExecutionMode() == ToolExecutionMode.SEQUENTIAL) {
       responseEventsFlowable =
-          Flowable.fromIterable(functionCalls).concatMapMaybe(functionCallMapper);
-
+          Flowable.fromIterable(functionCalls)
+              .concatMapMaybe(call -> functionCallMapper.apply(call));
     } else {
       responseEventsFlowable =
-          Flowable.fromIterable(functionCalls).flatMapMaybe(functionCallMapper);
+          Flowable.fromIterable(functionCalls)
+              .concatMapEager(call -> functionCallMapper.apply(call).toFlowable());
     }
 
     return responseEventsFlowable