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refactor: Use Maybe instead of Single<Optional> #996

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Merged
copybara-service merged 1 commit into from
Mar 10, 2026
Merged

refactor: Use Maybe instead of Single<Optional> #996

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61 changes: 29 additions & 32 deletions core/src/main/java/com/google/adk/agents/BaseAgent.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,6 @@
import io.reactivex.rxjava3.core.Completable;
import io.reactivex.rxjava3.core.Flowable;
import io.reactivex.rxjava3.core.Maybe;
import io.reactivex.rxjava3.core.Single;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
Expand Down Expand Up @@ -316,30 +315,29 @@ private Flowable<Event> run(
() -> {
InvocationContext invocationContext = createInvocationContext(parentContext);

Flowable<Event> mainAndAfterEvents =
Flowable.defer(() -> runImplementation.apply(invocationContext))
.concatWith(
Flowable.defer(
() ->
callCallback(
afterCallbacksToFunctions(
invocationContext.pluginManager(), afterAgentCallback),
invocationContext)
.toFlowable()));

return callCallback(
beforeCallbacksToFunctions(
invocationContext.pluginManager(), beforeAgentCallback),
invocationContext)
.flatMapPublisher(
beforeEventOpt -> {
beforeEvent -> {
if (invocationContext.endInvocation()) {
return Flowable.fromOptional(beforeEventOpt);
return Flowable.just(beforeEvent);
}

Flowable<Event> beforeEvents = Flowable.fromOptional(beforeEventOpt);
Flowable<Event> mainEvents =
Flowable.defer(() -> runImplementation.apply(invocationContext));
Flowable<Event> afterEvents =
Flowable.defer(
() ->
callCallback(
afterCallbacksToFunctions(
invocationContext.pluginManager(), afterAgentCallback),
invocationContext)
.flatMapPublisher(Flowable::fromOptional));

return Flowable.concat(beforeEvents, mainEvents, afterEvents);
return Flowable.just(beforeEvent).concatWith(mainAndAfterEvents);
})
.switchIfEmpty(mainAndAfterEvents)
.compose(
Tracing.traceAgent(
"invoke_agent " + name(), name(), description(), invocationContext));
Expand Down Expand Up @@ -383,13 +381,13 @@ private <T> ImmutableList<Function<CallbackContext, Maybe<Content>>> callbacksTo
*
* @param agentCallbacks Callback functions.
* @param invocationContext Current invocation context.
* @return single emitting first event, or empty if none.
* @return maybe emitting first event, or empty if none.
*/
private Single<Optional<Event>> callCallback(
private Maybe<Event> callCallback(
List<Function<CallbackContext, Maybe<Content>>> agentCallbacks,
InvocationContext invocationContext) {
if (agentCallbacks.isEmpty()) {
return Single.just(Optional.empty());
return Maybe.empty();
}

CallbackContext callbackContext =
Expand All @@ -404,21 +402,20 @@ private Single<Optional<Event>> callCallback(
.map(
content -> {
invocationContext.setEndInvocation(true);
return Optional.of(
Event.builder()
.id(Event.generateEventId())
.invocationId(invocationContext.invocationId())
.author(name())
.branch(invocationContext.branch().orElse(null))
.actions(callbackContext.eventActions())
.content(content)
.build());
return Event.builder()
.id(Event.generateEventId())
.invocationId(invocationContext.invocationId())
.author(name())
.branch(invocationContext.branch().orElse(null))
.actions(callbackContext.eventActions())
.content(content)
.build();
})
.toFlowable();
})
.firstElement()
.switchIfEmpty(
Single.defer(
Maybe.defer(
() -> {
if (callbackContext.state().hasDelta()) {
Event.Builder eventBuilder =
Expand All @@ -429,9 +426,9 @@ private Single<Optional<Event>> callCallback(
.branch(invocationContext.branch().orElse(null))
.actions(callbackContext.eventActions());

return Single.just(Optional.of(eventBuilder.build()));
return Maybe.just(eventBuilder.build());
} else {
return Single.just(Optional.empty());
return Maybe.empty();
}
}));
}
Expand Down
84 changes: 40 additions & 44 deletions core/src/main/java/com/google/adk/flows/llmflows/BaseLlmFlow.java
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Original file line number Diff line number Diff line change
Expand Up @@ -170,52 +170,51 @@ private Flowable<LlmResponse> callLlm(
LlmRequest.Builder llmRequestBuilder = llmRequest.toBuilder();

return handleBeforeModelCallback(context, llmRequestBuilder, eventForCallbackUsage)
.flatMapPublisher(
beforeResponse -> {
if (beforeResponse.isPresent()) {
return Flowable.just(beforeResponse.get());
}
BaseLlm llm =
agent.resolvedModel().model().isPresent()
? agent.resolvedModel().model().get()
: LlmRegistry.getLlm(agent.resolvedModel().modelName().get());
return llm.generateContent(
llmRequestBuilder.build(),
context.runConfig().streamingMode() == StreamingMode.SSE)
.onErrorResumeNext(
exception ->
handleOnModelErrorCallback(
context, llmRequestBuilder, eventForCallbackUsage, exception)
.switchIfEmpty(Single.error(exception))
.toFlowable())
.doOnNext(
llmResp ->
Tracing.traceCallLlm(
context,
eventForCallbackUsage.id(),
llmRequestBuilder.build(),
llmResp))
.doOnError(
error -> {
Span span = Span.current();
span.setStatus(StatusCode.ERROR, error.getMessage());
span.recordException(error);
})
.compose(Tracing.trace("call_llm"))
.concatMap(
llmResp ->
handleAfterModelCallback(context, llmResp, eventForCallbackUsage)
.toFlowable());
});
.toFlowable()
.switchIfEmpty(
Flowable.defer(
() -> {
BaseLlm llm =
agent.resolvedModel().model().isPresent()
? agent.resolvedModel().model().get()
: LlmRegistry.getLlm(agent.resolvedModel().modelName().get());
return llm.generateContent(
llmRequestBuilder.build(),
context.runConfig().streamingMode() == StreamingMode.SSE)
.onErrorResumeNext(
exception ->
handleOnModelErrorCallback(
context, llmRequestBuilder, eventForCallbackUsage, exception)
.switchIfEmpty(Single.error(exception))
.toFlowable())
.doOnNext(
llmResp ->
Tracing.traceCallLlm(
context,
eventForCallbackUsage.id(),
llmRequestBuilder.build(),
llmResp))
.doOnError(
error -> {
Span span = Span.current();
span.setStatus(StatusCode.ERROR, error.getMessage());
span.recordException(error);
})
.compose(Tracing.trace("call_llm"))
.concatMap(
llmResp ->
handleAfterModelCallback(context, llmResp, eventForCallbackUsage)
.toFlowable());
}));
}

/**
* Invokes {@link BeforeModelCallback}s. If any returns a response, it's used instead of calling
* the LLM.
*
* @return A {@link Single} with the callback result or {@link Optional#empty()}.
* @return A {@link Maybe} with the callback result.
*/
private Single<Optional<LlmResponse>> handleBeforeModelCallback(
private Maybe<LlmResponse> handleBeforeModelCallback(
InvocationContext context, LlmRequest.Builder llmRequestBuilder, Event modelResponseEvent) {
Event callbackEvent = modelResponseEvent.toBuilder().build();
CallbackContext callbackContext =
Expand All @@ -228,7 +227,7 @@ private Single<Optional<LlmResponse>> handleBeforeModelCallback(

List<? extends BeforeModelCallback> callbacks = agent.canonicalBeforeModelCallbacks();
if (callbacks.isEmpty()) {
return pluginResult.map(Optional::of).defaultIfEmpty(Optional.empty());
return pluginResult;
}

Maybe<LlmResponse> callbackResult =
Expand All @@ -238,10 +237,7 @@ private Single<Optional<LlmResponse>> handleBeforeModelCallback(
.concatMapMaybe(callback -> callback.call(callbackContext, llmRequestBuilder))
.firstElement());

return pluginResult
.switchIfEmpty(callbackResult)
.map(Optional::of)
.defaultIfEmpty(Optional.empty());
return pluginResult.switchIfEmpty(callbackResult);
}

/**
Expand Down