[anthropic] fix issue #1370 with tool call duplication

Without this fix during the stream event handling when `EventType.MESSAGE_STOP` occurs, the latest content block was resent again and it caused to the additional tool call(if it was the latest event)

Author: mmazurkevich

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

@@ -179,7 +179,13 @@ else if (event.type().equals(EventType.MESSAGE_DELTA)) {
 			}
 		}
 		else if (event.type().equals(EventType.MESSAGE_STOP)) {
-			// pass through
+			// Don't return the latest Content block as it was before. Instead, return it with an updated event
+			// type and general information like: model, message type, id and usage
+			contentBlockReference.get()
+					.withType(event.type().name())
+					.withContent(List.of())
+					.withStopReason(null)
+					.withStopSequence(null);
 		}
 		else {
 			contentBlockReference.get().withType(event.type().name()).withContent(List.of());

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

@@ -16,10 +16,12 @@
 
 package org.springframework.ai.anthropic.api;
 
+import java.util.ArrayList;
 import java.util.List;
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
+import org.springframework.ai.model.ModelOptionsUtils;
 import reactor.core.publisher.Flux;
 
 import org.springframework.ai.anthropic.api.AnthropicApi.AnthropicMessage;
@@ -41,6 +43,25 @@ public class AnthropicApiIT {
 
 	AnthropicApi anthropicApi = new AnthropicApi(System.getenv("ANTHROPIC_API_KEY"));
 
+	List<AnthropicApi.Tool> tools = List.of(new AnthropicApi.Tool("getCurrentWeather",
+			"Get the weather in location. Return temperature in 30°F or 30°C format.", ModelOptionsUtils.jsonToMap("""
+					{
+						"type": "object",
+						"properties": {
+							"location": {
+								"type": "string",
+								"description": "The city and state e.g. San Francisco, CA"
+							},
+							"unit": {
+								"type": "string",
+								"enum": ["C", "F"]
+							}
+						},
+						"required": ["location", "unit"]
+					}
+					""")));
+
+
 	@Test
 	void chatCompletionEntity() {
 
@@ -72,6 +93,46 @@ void chatCompletionStream() {
 		bla.stream().forEach(r -> System.out.println(r));
 	}
 
+	@Test
+	void chatCompletionStreamWithToolCall() {
+		List<AnthropicMessage> messageConversation = new ArrayList<>();
+
+		AnthropicMessage chatCompletionMessage = new AnthropicMessage(List.of(new ContentBlock(
+				"What's the weather like in San Francisco? Show the temperature in Celsius.")),
+				Role.USER);
+
+		messageConversation.add(chatCompletionMessage);
+
+		ChatCompletionRequest chatCompletionRequest = ChatCompletionRequest.builder()
+				.withModel(AnthropicApi.ChatModel.CLAUDE_3_OPUS)
+				.withMessages(messageConversation)
+				.withMaxTokens(1500)
+				.withStream(true)
+				.withTemperature(0.8)
+				.withTools(tools)
+				.build();
+
+		List<ChatCompletionResponse> responses = this.anthropicApi.chatCompletionStream(chatCompletionRequest)
+				.collectList()
+				.block();
+
+		// Check that tool uses response returned only once
+		List<ChatCompletionResponse> toolCompletionResponses = responses.stream().filter(r ->
+				r.stopReason() != null && r.stopReason().equals(ContentBlock.Type.TOOL_USE.value)).toList();
+		assertThat(toolCompletionResponses).size().isEqualTo(1);
+		List<ContentBlock> toolContentBlocks = toolCompletionResponses.get(0).content();
+		assertThat(toolContentBlocks).size().isEqualTo(1);
+		ContentBlock toolContentBlock = toolContentBlocks.get(0);
+		assertThat(toolContentBlock.type()).isEqualTo(ContentBlock.Type.TOOL_USE);
+		assertThat(toolContentBlock.name()).isEqualTo("getCurrentWeather");
+
+		// Check that message stop response also returned
+		List<ChatCompletionResponse> messageStopEvents = responses.stream()
+				.filter(r -> r.type().equals(AnthropicApi.EventType.MESSAGE_STOP.name()))
+				.toList();
+		assertThat(messageStopEvents).size().isEqualTo(1);
+	}
+
 	@Test
 	void chatCompletionStreamError() {
 		AnthropicMessage chatCompletionMessage = new AnthropicMessage(List.of(new ContentBlock("Tell me a Joke?")),