Middleware Architecture

[gakonst]

Is your feature request related to a problem? Please describe.

So far, we're adding plugins to the Client / Provider by adding optional variables (e.g. Signer, ENS, Gas Oracle, Nonce Manager). Instead, we could have a trait Client which would require implementing all JSON-RPC methods. Then, each time you want to write a plug-in, you would implement the method you need (e.g. for ENS methods, you'd resolve to/from from names to addresses) and then you'd pass the data to the same function in the next level (e.g. self.inner.send_transaction). This seems straightforward to do with 2 exceptions

1. It is cumbersome to have to re-implement every trait method when creating wrapper structs. It'd be nice if we can have some smart way (e.g. a macro) which does trait delegation. Unfortuntely, due to using
2. Error handling: We cannot have a variant in a thiserror like InnerError(#[from] I::Error) because it potentially allows for a recursive type.

Describe the solution you'd like

A middleware-based architecture for sending RPC requests which allows creating new middleware wrappers "easily", ideally w/o having to write a lot of boilerplate which does delegation to each inner layer manually.

Then, we'd be able to do:

let provider = Provider::new("http://localhost:8545");
let provider = SignerMiddleware::new("privateKey", provider);
let provider = NonceManagerMiddleware::new(provider);
let provider = GasEscalatorMiddleware::new(provider);
let provider = EnsMiddleware::new(provider);

...and so on

Describe alternatives you've considered

So far, I've tried implementing this here: #65.

[gakonst]

Fixed in #65