Is it safe to update an interface when upgrading a contract?

Support Upgrades
,
1

Hello,
I have the following upgradeable contract:

import "./IMyCustomErc20.sol";

contract MyContract is UUPSUpgradeable {

    /// @custom:storage-location erc7201:storage.MyContract
    struct MyContractStorage {
        IMyCustomErc20 customErc20;
    }

    // keccak256(abi.encode(uint256(keccak256("storage.MyContract")) - 1)) & ~bytes32(uint256(0xff))
    bytes32 private constant MyContractStorageLocation =
        0xba46220259871765522240056f76631a28aa19c5092d6dd51d6b858b4ebcb300;

    function _getMyContractStorage() private pure returns (MyContractStorage storage $) {
        assembly {
            $.slot := MyContractStorageLocation
        }
    }

    function initialize(address _customErc20) public {
        MyContractStorage storage $ = _getMyContractStorage();
        $.customErc20 = IMyCustomErc20(_customErc20);
    }
}

Now let's say that I add some new functionality to my other contract (the MyCustomErc20Token) and I update the IMyCustomErc20 interface. Do I need to update MyContract to support the new interface like this?

import "./IMyCustomErc20.sol";
import "./IMyCustomErc20V2.sol";
....

/// @custom:storage-location erc7201:storage.MyContract
struct MyContractStorage {
   IMyCustomErc20 customErc20;
   IMyCustomErc20V2 customErc20V2;
}

....

or can I just update the IMyCustomErc20 file without creating a V2 version and my contract will support by default all the new changes I made?

Are there any potential storage issues after upgrading or any other issues to be aware of if the change of the interface doesn't affect storage conflicts?

2

Your variable for IMyCustomErc20 customErc20; just stores the address of your other contract, and it looks like you are consuming it from MyContract. So in this case you should ensure that your other contract's interface and logic (IMyCustomErc20 and MyCustomErc20Token) remain backwards compatible with the contract that you are consuming it from (MyContract), or update its usage in MyContract to match.