Not only should you replace this because it’s leaking, you should replace it because it’s an absolute Frankenstein of a connection and is bound to fail at some point or another.
The photo isn’t clear, but it looks like at the metal strap there isn’t a 45° fitting but the “plumber” soldered a piece of soft copper tubing inside a copper pipe without any sort of coupling.
If this is the case, even if it was soldered perfectly, the flow of the water is hitting the edge of the piping and becoming turbulent (assuming the water is flowing right to left), increasing the wear on the soft copper pipe, which may be what’s causing the corrosion further along the pipe.
Even if that’s not the case, the fact there is a leak at the metal strap is further hastening the corrosion due to the fact that those straps are usually only copper plated steel and the copper plating adjacent to the corrosion is long gone by now. With dissimilar metals adjacent to each other and a little drop of “electrolyte” (particularly if you have hard water or a water softener) you’re getting ion exchange and it’s only a matter of time before they both corrode away.
By the way that blue color is a mix of all the copper salts from reacting with what’s in the water, copper chloride, hydroxide, fluoride (if the city adds fluoride to the water) and oxides. All of them are removing copper, ion by ion from your pipe and making it weaker!
Don’t wait, fix it while you have the wall open!