feature: contract revert trait

[prestwich]

Motivation

Followup work to #2172. Allows easier decoding of error types for generated contracts

Solution

• Introduce the ContractRevert trait
• Auto-derive ContractRevert on the error enum in abigen! contract modules
• Add RevertString(String) to contract error enum in abigen! contract modules
• Add ContractError::decode_contract_revert<Err: ContractRevert(&self) -> Option<Err>
• (drive-by) add missing FromIterator impls to ethers::core::types::Bytes

This is a breaing change to abigen! generated bindings (again) but i promise this one is also really good :)

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog
• Breaking changes

[prestwich]

will address these comments tomorrow. ledger issue has worn my brain out

[gakonst]

Shouldn't this be below the if let Ok in the macro below? So that we only decode as string as a fallback vs prioritizing it?

[prestwich]

This implementation has never been safe for users to access directly, as it does not include selector information, and ABI encoded types are incredibly ambiguous. It has always thrown bad false positives.

My belief is that strings will be more common than other error types, even for contracts that do not revert, so putting a string in the first attempt results in the fewest decode attempts

[mattsse]

is this only derived for enums?
because this clashes with EthError

[prestwich]

yes, this trait is only for unifying multiple potential ethereum errors into 1 type. Basically this should be thought of as "the errors associated with a specific contract's ABI".

I thought about breaking out a super-trait that had the shared methods on it, and decided that it was too complex for users

[prestwich]

i also thought about modifying AbiDecode to include decode_with_selector(selector: Selector, bytes: &[u8]) but didn't want to get into lower level changes

[prestwich]

you can also consult the docstring, btw

/// A trait for enums unifying [`EthError`] types.
///
/// We do not recommend manual implementations of this trait. Instead, use the
/// automatically generated implementation in the [`crate::abigen`] macro```

[gakonst]

good w/ me pending any more matt feedback

[prestwich]

this is now based on latest master 👍

[gakonst]

@prestwich seems to have broken in the Seaport codegen

---- abigen::can_generate_seaport_1_0 stdout ----
error: test failed, to rerun pass `-p ethers-contract --test it`
thread 'abigen::can_generate_seaport_1_0' panicked at 'checked by len: TryFromSliceError(())', /home/runner/work/ethers-rs/ethers-rs/ethers-contract/src/error.rs:32:40
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[prestwich]

@gakonst seaport is fixed now 👍