fix(openai): handle empty mode values in azure openai streaming responses (#14417)

Fixed an issue where the OpenAI model tag was not being updated when the
first chunk contained an empty model value but subsequent chunks
contained the actual model name.

MLOS-219.
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Author: XG-xin

ddtrace/contrib/internal/openai/utils.py

@@ -116,7 +116,7 @@ def _loop_handler(span, chunk, streamed_chunks):
     When handling a streamed chat/completion/responses,
     this function is called for each chunk in the streamed response.
     """
-    if span.get_tag("openai.response.model") is None:
+    if not span.get_tag("openai.response.model"):
         if hasattr(chunk, "type") and chunk.type.startswith("response."):
             response = getattr(chunk, "response", None)
             model = getattr(response, "model", "")

releasenotes/notes/handle-empty-openai-model-be224ae61d71f5ea.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    openai: This fix resolves an issue where the model name was not captured in streamed responses that specified the model name in non-initial chunks.

tests/contrib/openai/test_openai_llmobs.py

@@ -508,7 +508,7 @@ def test_chat_completion_azure_streamed(
         mock_llmobs_writer.enqueue.assert_called_with(
             _expected_llmobs_llm_span_event(
                 span,
-                model_name="gpt-4o-mini",
+                model_name="gpt-4o-mini-2024-07-18",
                 model_provider="azure_openai",
                 input_messages=input_messages,
                 # note: investigate why role is empty; in the streamed chunks there is no role returned.