Feature request: sign digest method in Signer

Description

The request is to basically offer the functionality you described in this comment as a method in the Signer class.

Just like there is a signMessage method, it’d be nice to have a similar signDigest, which takes the raw digest (a 32 bytes hash) and returns a signature as a JavaScript object with the v, r and s properties.

Use Case

This would be particularly useful for testing contracts that implement EIP-712 and EIP-2612.

A comprehensive testing suite involves many networks: the local chain, the coverage chain, maybe a testnet or a fork of mainnet. Having a signDigest method in the Signer would simplify the writing of tests, insofar developers wouldn’t have to manage a mapping of private keys => accounts for each network. Furthermore, there are tools where the default behaviour is to create a new set of accounts on every run (e.g. solidity-coverage), so additional configuration is required to make them compatible with tests that involve hardcoded private keys.

[ricmoo]

As a note to anyone following this issue, #687 has been addressed. Please try out EIP-712 support. 😃

[ricmoo]

Closing this and tracking progress in #687 .

Thanks! 😃