[Feature]: Investigate How to Address export-abi Warnings

[0xNeshi]

What is the feature you would like to see?

By declaring export-abi feature, we can remove those pesky warnings.
The problem is that cargo hack workflow fails when it tried to activate this feature with the trait `SolError` is not implemented for `[OUR_ERROR_NAME]` .
We should investigate why this is, so that we can declare the feature in Cargo.toml.

Alternatively, we can simply skip this feature, just as we do for std.

Original comment: #437 (comment)

Related #436

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[0xNeshi]

Declaring the export-abi feature in all relevant _Cargo.toml_s, and running cargo doc or cargo check with this feature enabled results in the following errors (I specifically ran RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --no-deps --all-features):

• all our contract functions that return Self::Error as part of their result (i.e. Result<[some_type], Self::Error>) fail with the following (example for ownable_two_step.rs):

error[E0220]: associated type `Error` not found for `Self`
   --> contracts/src/access/ownable_two_step.rs:158:27
    |
158 |     ) -> Result<(), Self::Error> {
    |                                       ^^^^^ associated type `Error` not found

Mitigation: this is a very weird error that is solved using a fully-qualified path for Self, like: Result<(), <Self as IOwnable2Step>::Error>. I presume this is an issue in #[public] macro, as this error only appears when --export-abi feature is enabled.

• The already reported "SolError is not implemented" error appears for various errors, e.g. for ownable_two_step.rs:

error[E0277]: the trait bound `ownable::Error: SolError` is not satisfied
  --> contracts/src/access/ownable_two_step.rs:48:13
   |
48 |     Ownable(OwnableError),
   |             ^^^^^^^^^^^^ the trait `SolError` is not implemented for `ownable::Error`
   |
   = help: the following other types implement trait `SolError`:
             AccessControlBadConfirmation
             AccessControlUnauthorizedAccount
             CheckpointUnorderedInsertion
             ECDSAInvalidSignature
             ECDSAInvalidSignatureS
             ERC1155InsufficientBalance
             ERC1155InvalidApprover
             ERC1155InvalidArrayLength
           and 39 others

What's worth noting is that this error only appears for the wrapped errors from other contracts. In other words, in each place where we "inherit" errors from another contract to be able to wrap and return them, SolError is not implemented (it is implemented only for those errors defined within sol! macro), and as the --export-abi feature requires all errors to implement it, we get an issue.
@bidzyyys @qalisander this is an important point! Since ABI's cannot be generated by the SDK for our contracts, this could mean that our contracts could be undeployable (EDIT: Our contracts are deployable, I checked, see edit at the end), and they just happen to pass local e2e tests!!

Did anyone try to actually deploy any of our contracts that inherit errors (e.g. Erc20Permit)?

@qalisander might this be related to a similar issue you raised with the Stylus team OffchainLabs/stylus-sdk-rs#135?

---

EDIT: I created a new Stylus project, set our lib as a dependency and created an Erc20Permit, as per our example. I then ran the following stylus CLI commands to see the results:

• cargo stylus check - passes ✔️
• cargo stylus deploy - passes 😌 ✔️
• cargo stylus export-abi - fails with our warnings turned into errors ❌

It seems we will need to handle this issue somehow, as users of our library won't be able to use the export-abi command.
Mitigation 1: Stylus team addresses OffchainLabs/stylus-sdk-rs#135 asap.
Mitigation 2: Instead of inheriting errors from other contracts through the enum Error, we inherit them by adding them one-by-one into the inheriting contract's error enum.
So instead of:

use crate::utils::cryptography::ecdsa;

pub enum Error {
    // ...
    ECDSA(ecdsa::Error),
}

We do:

use crate::utils::cryptography::ecdsa::{
    ECDSAInvalidSignature, ECDSAInvalidSignatureS,
};

pub enum Error {
    // ...
    // add errors directly
    InvalidSignature(ECDSAInvalidSignature),
    InvalidSignatureS(ECDSAInvalidSignatureS),
}

[0xNeshi]

To recap:

• Stylus SDK needs to support error inheritance feature: add possibility to reuse error for the other contract OffchainLabs/stylus-sdk-rs#135
• Our export-abi is possibly breaking due to some feature-related code in Stylus SDK https://openzeppelin.slack.com/archives/C06AE3YP0G7/p1733748790461619?thread_ts=1733475987.308549&cid=C06AE3YP0G7

Until these two are resolved, this issue is considered blocked