fix: chat stream returns an error response with a 'data: ' prefix (#396)

* fix: chat stream resp has 'data: ' prefix

* fix: lint error

* fix: lint error

* fix: lint error

chat_stream_test.go

@@ -178,6 +178,45 @@ func TestCreateChatCompletionStreamError(t *testing.T) {
 	t.Logf("%+v\n", apiErr)
 }
 
+func TestCreateChatCompletionStreamErrorWithDataPrefix(t *testing.T) {
+	client, server, teardown := setupOpenAITestServer()
+	defer teardown()
+	server.RegisterHandler("/v1/chat/completions", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/event-stream")
+
+		// Send test responses
+		//nolint:lll
+		dataBytes := []byte(`data: {"error":{"message":"The server had an error while processing your request. Sorry about that!", "type":"server_ error", "param":null,"code":null}}`)
+		dataBytes = append(dataBytes, []byte("\n\ndata: [DONE]\n\n")...)
+
+		_, err := w.Write(dataBytes)
+		checks.NoError(t, err, "Write error")
+	})
+
+	stream, err := client.CreateChatCompletionStream(context.Background(), ChatCompletionRequest{
+		MaxTokens: 5,
+		Model:     GPT3Dot5Turbo,
+		Messages: []ChatCompletionMessage{
+			{
+				Role:    ChatMessageRoleUser,
+				Content: "Hello!",
+			},
+		},
+		Stream: true,
+	})
+	checks.NoError(t, err, "CreateCompletionStream returned error")
+	defer stream.Close()
+
+	_, streamErr := stream.Recv()
+	checks.HasError(t, streamErr, "stream.Recv() did not return error")
+
+	var apiErr *APIError
+	if !errors.As(streamErr, &apiErr) {
+		t.Errorf("stream.Recv() did not return APIError")
+	}
+	t.Logf("%+v\n", apiErr)
+}
+
 func TestCreateChatCompletionStreamRateLimitError(t *testing.T) {
 	client, server, teardown := setupOpenAITestServer()
 	defer teardown()