Support returning multiple validation errors

[fenollp]

Today, validation ends on the first validation error encountered.

This asks that all validation errors be aggregated in some kind of collection, so all validation errors (or at least, as many as possible or that makes sense) are returned.

This can be behind a generation flag so both behaviors can be generated. Generating both at once (so both ways are available at runtime) should probably not be a goal.

[Adphi]

Maybe we could add a second method validate_all to the Validator trait.

[Adphi]

@fenollp It shouldn't be too hard to implement.
Do you want to give it a go?

[fenollp]

Hey! I'm down to have a go at this (and also the eventual other issues I open) but I need a hand.

Am I getting this right in that I should be adding a validate_all method to the trait, then edit this part for codegen

prost-validate/prost-validate-derive-core/src/derive.rs

Lines 56 to 70 in 49b5be3

	if !implementation.is_empty() {
	quote! {
	impl ::prost_validate::Validator for #path {
	#allow
	fn validate(&self) -> prost_validate::Result<()> {
	#implementation
	Ok(())
	}
	}
	}
	} else {
	quote! {
	impl ::prost_validate::Validator for #path {}
	}
	}

Then I should add a new variant say `ManyErrors(Vec<Box>) to https://docs.rs/prost-validate/latest/prost_validate/errors/enum.Error.html (or should it be un-Box-ed?, or a new error type altogether?)

Lastly, should this be under a plugin option and if so, where is this handled? I see many options mixed in and am getting lost.

Thanks!

[Adphi]

Yes, but I'm not sure if validate_all should be an additional method or an additional trait.

Maybe an Errors type that is a vector of Error.

Defaults to generate the validate_all method / trait for now. We can add an option for that later if needed.

Would you be interested in setting up a short call to go over it together ?