I've been exploring that (plus instant preview/eval, but that's another story) in a home-made language with a basic editor. For smaller files/modules it's totally feasible to do on every key press, fast enough to be fairly seamless.
It took a bit of getting used to, but there's something catchy about the experience, like molding clay - if the clay was made of a "smart material" that re-formed itself to an optimal shape.
The immediacy of working with self-reshaping code (and live reload too) reduces mental friction, so I can forget about formatting or compilation altogether. I hope more languages make it a part of the developer experience, IDE, etc.