Using abi.Interface with sighash selectors

[shazow]

Describe the Feature

Let's say I have an unverified contract with a bunch of sighash selector functions. I'd like to use ethers.abi.Interface instance or equivalent to build an interface for interacting with it in a generalized way (whether it's sighsahes or human-readable functions).

I'd like to build a frontend generator that takes Interface-like objects, so it shouldn't care whether functions are the original human-readable versions or sighash selectors.

Right now, Interface does not like this. Ideally, Interface shouldn't care whether I give it a human-readable function or a selector. Bonus points if Interface knows not to re-sighash a selector.

Perhaps there's a reason why Interface is incompatible with this, but I couldn't think of it. :)

Code Example

Via https://playground.ethers.org/


// This works fine
> iface = new utils.Interface(["function transferFrom(address, address, uint256)"]);
> iface.getFunction("0x23b872dd");
...

// This does not work
> iface = new utils.Interface(["function 0x23b872dd(address, address, uint256)"]);
"invalid identifier \"0x23b872dd\" (argument=\"value\", value=\"0x23b872dd\", code=INVALID_ARGUMENT, version=abi/5.7.0)"
> iface.getFunction("0x23b872dd");

[ricmoo]

I am moving this to the “Ideas” discussion. This is definitely not something that would go into v5.

It might take a lot of refactoring and thinking through the edge cases in order to incorporate it directly into the Unterface object (I would probably change the human-readable signature to "selector 0x12345678(address) returns (uint)", for example to delineate it and does not require hashing).

I think it would likely be a fairly easy third-party class to write though; the Fragment parser is fully exposed, you could use a regex to swap out the selector with the word “test” for example, process it as a normal Fragment (using Fragment.from) and then incorporate it using the _encodeParams and _decodeParams.

The v6 fragment might already make this much easier since it internalizes the selector. And if the name property was accessed you could throw.

I will mull over it more, but for now I would try out making a simple class that extends the Interface to see what gotchas there may be.

[shazow]

Sounds good!

I was surprised that Ethers cares whether a function is named something that starts a number, didn't realize that was part of the Solidity grammar specification!

I'll figure out a semi-compatible wrapper for now, not a problem. :)

[binares]

It'd be nice to be able to call such selector as well (if I only know the function's argument types). I assume there's no web3js equivalent to this either?

[shazow]

+1, I think we could still do it using the lower-level ethers.utils.AbiCoder helper directly to encode arguments and prepending the selector in front, but I don't think there's any higher-level helper functions that would work right now.