Add real Function Calling Streaming support

 - Add Java reflection merge utilities that can access  Azure private constructors and fields.
 - Azure merging, creation of flux windows.
 - Function call grouping for function processing.
 - Do not perform greedy operation on Flux.
 - Use "real" streaming on all client on function response.
 - Gerimi: fix missing method impl.
 - Mistral AI, OpenAI: fix missing stream flag in doCreateToolResponseRequest.
 - Fix code formatting. No wildcard imports.
 - Add Grogdunn to the javadoc authors.
 - Anthropic 3 API does not support streaming funciton calling yet.

Author: Grogdunn

models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatClient.java

@@ -450,4 +450,11 @@ protected boolean isToolFunctionCall(ResponseEntity<ChatCompletion> response) {
 		return response.getBody().content().stream().anyMatch(content -> content.type() == MediaContent.Type.TOOL_USE);
 	}
 
+	@Override
+	protected Flux<ResponseEntity<ChatCompletion>> doChatCompletionStream(ChatCompletionRequest request) {
+		// https://docs.anthropic.com/en/docs/tool-use
+		throw new UnsupportedOperationException(
+				"Streaming (stream=true) is not yet supported. We plan to add streaming support in a future beta version.");
+	}
+
 }

models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/api/AnthropicApi.java

@@ -29,6 +29,7 @@
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.retry.RetryUtils;
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatusCode;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.util.Assert;
@@ -100,7 +101,13 @@ public AnthropicApi(String baseUrl, String anthropicApiKey, String anthropicVers
 			.defaultStatusHandler(responseErrorHandler)
 			.build();
 
-		this.webClient = WebClient.builder().baseUrl(baseUrl).defaultHeaders(jsonContentHeaders).build();
+		this.webClient = WebClient.builder()
+			.baseUrl(baseUrl)
+			.defaultHeaders(jsonContentHeaders)
+			.defaultStatusHandler(HttpStatusCode::isError,
+					resp -> Mono.just(new RuntimeException("Response exception, Status: [" + resp.statusCode()
+							+ "], Body:[" + resp.bodyToMono(java.lang.String.class) + "]")))
+			.build();
 	}
 
 	/**

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/AnthropicChatClientIT.java

@@ -205,15 +205,15 @@ void functionCallTest() {
 			.withModel(AnthropicApi.ChatModel.CLAUDE_3_OPUS.getValue())
 			.withFunctionCallbacks(List.of(FunctionCallbackWrapper.builder(new MockWeatherService())
 				.withName("getCurrentWeather")
-				.withDescription("Get the weather in location")
+				.withDescription("Get the weather in location. Return temperature in 36°F or 36°C format.")
 				.build()))
 			.build();
 
 		ChatResponse response = chatClient.call(new Prompt(messages, promptOptions));
 
 		logger.info("Response: {}", response);
 
-		Generation generation = response.getResults().get(0);
+		Generation generation = response.getResult();
 		assertThat(generation.getOutput().getContent()).containsAnyOf("30.0", "30");
 		assertThat(generation.getOutput().getContent()).containsAnyOf("10.0", "10");
 		assertThat(generation.getOutput().getContent()).containsAnyOf("15.0", "15");

models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/AzureOpenAiChatClient.java

@@ -15,11 +15,6 @@
  */
 package org.springframework.ai.azure.openai;
 
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-
 import com.azure.ai.openai.OpenAIClient;
 import com.azure.ai.openai.models.ChatChoice;
 import com.azure.ai.openai.models.ChatCompletions;
@@ -33,15 +28,14 @@
 import com.azure.ai.openai.models.ChatRequestSystemMessage;
 import com.azure.ai.openai.models.ChatRequestToolMessage;
 import com.azure.ai.openai.models.ChatRequestUserMessage;
-import com.azure.ai.openai.models.ChatResponseMessage;
 import com.azure.ai.openai.models.CompletionsFinishReason;
 import com.azure.ai.openai.models.ContentFilterResultsForPrompt;
+import com.azure.ai.openai.models.FunctionCall;
 import com.azure.ai.openai.models.FunctionDefinition;
 import com.azure.core.util.BinaryData;
 import com.azure.core.util.IterableStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import reactor.core.publisher.Flux;
 
 import org.springframework.ai.azure.openai.metadata.AzureOpenAiChatResponseMetadata;
 import org.springframework.ai.chat.ChatClient;
@@ -59,6 +53,14 @@
 import org.springframework.ai.model.function.FunctionCallbackContext;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
+import reactor.core.publisher.Flux;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
  * {@link ChatClient} implementation for {@literal Microsoft Azure AI} backed by
@@ -68,6 +70,7 @@
  * @author Ueibin Kim
  * @author John Blum
  * @author Christian Tzolov
+ * @author Grogdunn
  * @see ChatClient
  * @see com.azure.ai.openai.OpenAIClient
  */
@@ -158,17 +161,42 @@ public Flux<ChatResponse> stream(Prompt prompt) {
 		IterableStream<ChatCompletions> chatCompletionsStream = this.openAIClient
 			.getChatCompletionsStream(options.getModel(), options);
 
-		return Flux.fromStream(chatCompletionsStream.stream()
+		Flux<ChatCompletions> chatCompletionsFlux = Flux.fromIterable(chatCompletionsStream);
+
+		final var isFunctionCall = new AtomicBoolean(false);
+		final var accessibleChatCompletionsFlux = chatCompletionsFlux
 			// Note: the first chat completions can be ignored when using Azure OpenAI
 			// service which is a known service bug.
 			.skip(1)
-			.map(ChatCompletions::getChoices)
-			.flatMap(List::stream)
+			.map(chatCompletions -> {
+				final var toolCalls = chatCompletions.getChoices().get(0).getDelta().getToolCalls();
+				isFunctionCall.set(toolCalls != null && !toolCalls.isEmpty());
+				return chatCompletions;
+			})
+			.windowUntil(chatCompletions -> {
+				if (isFunctionCall.get() && chatCompletions.getChoices()
+					.get(0)
+					.getFinishReason() == CompletionsFinishReason.TOOL_CALLS) {
+					isFunctionCall.set(false);
+					return true;
+				}
+				return false;
+			}, false)
+			.concatMapIterable(window -> {
+				final var reduce = window.reduce(MergeUtils.emptyChatCompletions(), MergeUtils::mergeChatCompletions);
+				return List.of(reduce);
+			})
+			.flatMap(mono -> mono);
+		return accessibleChatCompletionsFlux
+			.switchMap(accessibleChatCompletions -> handleFunctionCallOrReturnStream(options,
+					Flux.just(accessibleChatCompletions)))
+			.flatMapIterable(ChatCompletions::getChoices)
 			.map(choice -> {
-				var content = (choice.getDelta() != null) ? choice.getDelta().getContent() : null;
+				var content = Optional.ofNullable(choice.getMessage()).orElse(choice.getDelta()).getContent();
 				var generation = new Generation(content).withGenerationMetadata(generateChoiceMetadata(choice));
 				return new ChatResponse(List.of(generation));
-			}));
+			});
+
 	}
 
 	/**
@@ -522,9 +550,17 @@ protected List<ChatRequestMessage> doGetUserMessages(ChatCompletionsOptions requ
 
 	@Override
 	protected ChatRequestMessage doGetToolResponseMessage(ChatCompletions response) {
-		ChatResponseMessage responseMessage = response.getChoices().get(0).getMessage();
+		final var accessibleChatChoice = response.getChoices().get(0);
+		var responseMessage = Optional.ofNullable(accessibleChatChoice.getMessage())
+			.orElse(accessibleChatChoice.getDelta());
 		ChatRequestAssistantMessage assistantMessage = new ChatRequestAssistantMessage("");
-		assistantMessage.setToolCalls(responseMessage.getToolCalls());
+		final var toolCalls = responseMessage.getToolCalls();
+		assistantMessage.setToolCalls(toolCalls.stream().map(tc -> {
+			final var tc1 = (ChatCompletionsFunctionToolCall) tc;
+			var toDowncast = new ChatCompletionsFunctionToolCall(tc.getId(),
+					new FunctionCall(tc1.getFunction().getName(), tc1.getFunction().getArguments()));
+			return ((ChatCompletionsToolCall) toDowncast);
+		}).toList());
 		return assistantMessage;
 	}
 
@@ -533,6 +569,11 @@ protected ChatCompletions doChatCompletion(ChatCompletionsOptions request) {
 		return this.openAIClient.getChatCompletions(request.getModel(), request);
 	}
 
+	@Override
+	protected Flux<ChatCompletions> doChatCompletionStream(ChatCompletionsOptions request) {
+		return Flux.fromIterable(this.openAIClient.getChatCompletionsStream(request.getModel(), request));
+	}
+
 	@Override
 	protected boolean isToolFunctionCall(ChatCompletions chatCompletions) {
 
@@ -549,4 +590,4 @@ protected boolean isToolFunctionCall(ChatCompletions chatCompletions) {
 		return choice.getFinishReason() == CompletionsFinishReason.TOOL_CALLS;
 	}
 
-}
+}