Add mode for continous parsing (not on-save)

[conjurationspellsoneone]

One of the rough aspects of using scala over other languages like TypeScript is how sluggish it feels in the IDE, which I think is primarily due to Metal's not providing error detection / type analysis in real-time, instead requiring you to save the file every time.

And enabling interval auto-save for my IDE is also not a solution as I work in hot-reloaded contexts where I don't want to be distracted by broken code errors in the output half-way through, and also there are simply many contexts where this doesn't work.

For example
suppose function foo has 3 arguments, and I am in the middle of typing it, only provided one argument so far

if foo(bar.baz, 

but I am not quite sure if .baz is the right property on bar. I can't do ctrl + save yet, because I know for sure that the whole line will error because I am missing the next two arguments of foo. But until I ctrl + save, I won't know if bar.baz is an error.

In TypeScript an Python where syntax and type analysis is continuously provided on every keystroke, this is not an issue and it feels very fluid.

Regardless, this is a clear divide in preference among developers so supporting both is a good idea.

It would be great if you provided a setting flag to enable this method for the many developers who prefer it.

[tgodzik]

Thanks for reporting. Do you mean that you would want to see type errors from the compiler instead of only parsing error in metals?

I will move it to metals feature request as this repository really only deals with parsing