Fix: Tool Call chunk merging fails for APIs returning empty string IDs

[Yuumi-zoomie]

Bug description
Inside org.springframework.ai.openai.api.OpenAiStreamFunctionCallingHelper at line 114:

			if (currentToolCall.id() != null) {   //HERE
				if (lastPreviousTooCall != null) {
					toolCalls.add(lastPreviousTooCall);
				}
				toolCalls.add(currentToolCall);
			}
			else {
				toolCalls.add(merge(lastPreviousTooCall, currentToolCall));
			}

The current logic for merging ToolCallChunk streams assumes that the tool call ID will be null. However, some API implementations, such as Aliyun Model Studio, return an empty string ("") instead.

This discrepancy causes the merge logic to fail, preventing partial tool call chunks from being correctly assembled into a single function call.

A simple fix is to change the null check to a more robust blank string check (e.g., StringUtils.isBlank()). This will resolve the issue with Aliyun models and improve the overall compatibility of Spring AI with different API providers.

[sunyuhan1998]

I guess you're currently not using the latest version of Spring AI? Actually, this issue has already been fixed in the latest code:

spring-ai/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiStreamFunctionCallingHelper.java

Lines 126 to 134 in 940bcf3

	if (StringUtils.hasText(currentToolCall.id())) {
	if (lastPreviousTooCall != null) {
	toolCalls.add(lastPreviousTooCall);
	}
	toolCalls.add(currentToolCall);
	}
	else {
	toolCalls.add(merge(lastPreviousTooCall, currentToolCall));
	}

[Yuumi-zoomie]

@sunyuhan1998, yes I'm using spring-ai-openai-spring-boot-starter version 1.0.0-M6