I set a low value of 1 for my spinner. It stops the user from using the arrow keys to enter a 0 quantity, however if the user types in a quantity the no checking is done to validate the value. This is the case for both the form spinner and the edit in place one. If I use the number type (and the browser adds the arrows) everything works as expected.
Edit: I added the validation code by hand, and confirmed that the generated code is just missing if it's a spinner type.