Can't retrieve constants behind proxy

[juliancabmar]

Hello to all. I have a doubt about how retrieve a constant on implementation behind a UUPS proxy pattern. Here is my contract:

import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";

// Implementation V1
contract MyContractV1 is Initializable, UUPSUpgradeable {
    uint256 public value;
    uint256 public WAGE_L1 = 35;

    // Initializer function (replaces constructor)
    function initialize(uint256 _value) public initializer {
        __UUPSUpgradeable_init();
        value = _value;
    }

    // Required by UUPSUpgradeable to authorize upgrades
    function _authorizeUpgrade(address newImplementation) internal override {}

    // Function to update the value
    function setValue(uint256 _value) public onlyOwner {
        value = _value;
    }
}

And tis is my test:

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.8.26;

import {Test, console2} from "forge-std/Test.sol";
import {MyContractV1, MyContractV2} from "./Aux.sol";
import {ERC1967Proxy} from "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";

contract AuditTests is Test {
    ERC1967Proxy proxy;
    MyContractV1 implementOne;
    MyContractV2 implementTwo;

    function testAux() public {
        // Deploy One
        implementOne = new MyContractV1();
        // Deploy proxy and pass One address how first implementation
        proxy = new ERC1967Proxy(address(implementOne), "");
        // Call the initializer function on new implementation
        address(proxy).call(abi.encodeCall(implementOne.initialize, (666)));
        // Call WAGE_L1 constant
        (, bytes memory wageL1) = address(proxy).call(abi.encodeCall(implementOne.WAGE_L1, ()));
        console2.log("WAGE_L1:", abi.decode(wageL1, (uint256)));
    }
}

And allways obtain:

Logs:
  WAGE_L1: 0

I know that is unnecessary complicate code, but I want to use call instead of MyContractV1(address(proxy))... sorry :)

[EngrPips]

@juliancabmar If you do this MyContractV1(address(proxy)) do you get the expected value?

[EngrPips]

Interesting, check that if you retrieve the value you initialized, you will get the expected value.

[juliancabmar]

Yes, this work...

function testAux() public {
        // Deploy One
        implementOne = new MyContractV1();
        // Deploy proxy and pass One address how first implementation
        proxy = new ERC1967Proxy(address(implementOne), "");
        // Call the initializer function on new implementation
        address(proxy).call(abi.encodeCall(implementOne.initialize, (666)));
        // Call value
        (, bytes memory value) = address(proxy).call(abi.encodeCall(implementOne.value, ()));
        console2.log("value:", abi.decode(value, (uint256)));
    }

OR

function testAux() public {
        // Deploy One
        implementOne = new MyContractV1();
        // Deploy proxy and pass One address how first implementation
        proxy = new ERC1967Proxy(address(implementOne), "");
        // Call the initializer function on new implementation
        address(proxy).call(abi.encodeCall(implementOne.initialize, (666)));
        
        console2.log("value: ", MyContractV1(address(proxy)).value());
    }

Give me

Logs:
  value: 666

It seems there are no getters for public constants 🫤

[juliancabmar]

If I write a getter:

function getWageL1() public view returns (uint256) {
        return WAGE_L1;
    }

and call it from the test:

console2.log("WAGE_L1:", MyContractV1(address(proxy)).getWageL1());

It doesn't work either:

Logs:
  WAGE_L1: 0

[EngrPips]

constant and immutable variables do not take a storage slot, as their value is imprinted in the bytecode of the smart contract, so the WAGE_L1 will be stored in the bytecode of the implementOne contract and not in any storage slot and I think that is why you are unable to retrieve it through the proxy. Try calling the getWageL1 function on the implementOne contract directly, and I expect that you will get the appropriate value returned.

[juliancabmar]

Hi @EngrPips! Yes, it does... but if we have to use the implementation contract directly, the proxy lost his meaning.
Thanks a lot for help me to dig on this.

[EngrPips]

You know, making the implementation contract have a constant variable violates the principle of upgradeable contracts to start with