Custom trait implementation

[Artemka374]

In OpenBrush 4.0-beta it is possible to avoid boilerplate code with usage of implementation macro, but currently it only works with OpenBrush native traits. If some projects want to separate logics of custom trait implementation and actual contract file, there will still be a lot of boilerplate code, that should be written manually. We can resolve this issue in the following way:

1. Create something like trait_implementation macro that will be used on TraitImpl. It will have the parameter - the actual trait naming, for which implementation is described.
2. trait_implementation macro will generate functional macro, like trait_impl!(Contract) that will generate

impl Trait for Contract {
	#[ink(message)]
	fn message(&self) {
		TraitImpl::message(self)
	}
}

3. This macro can be integrated in implementation macro, and it will use it on storage struct
4. Macro does not allow overriding the implementation, but could reduce a lot amount of boilerplate code in contract implementations.

[PierreOssun]

Seems reasonable like this but how do you deal with payable functions ?

[deuszx]

Thanks for starting this. IMHO all solutions will be stubs while we wait for the proper/fix of the trait system in ink! itself. Tracking issue: use-ink/ink#1689

[Artemka374]

Seems reasonable like this but how do you deal with payable functions ?

We can add the payable marker that will work inside the trait_implementation macro, so messages that are payable will be generated also as #[ink(payable)]

[Artemka374]

Thanks for starting this. IMHO all solutions will be stubs while we wait for the proper/fix of the trait system in ink! itself. Tracking issue: paritytech/ink#1689

That's true, but until this issue in ink! is not fixed, we still can implement our own solution for this