Anyone going in can ask any of the stall owner. They know. As I recalled, there was once, I think 3rd day of CNY, stall owner told me not to come as there wont be anyone. So best ask around
At Johor Jaya, some 3 weeks before CNY got CNY market. Better go on Tuesday as it is Pasar Malam night. Last year, a week before CNY, the Pasar Malam was extended for the entire week. But not all stores participated (for the rest of the week). It was made opened for all but some didn't participate as I was told.
The CNY market, don't expect too much, it is something like a small scale Chinatown. Rather quiet on weekdays as I was there a week before CNY.. It more lively on a Sunday morning where the Pasar Pagi is on. That was my observation.