How to upgrade a contract deployed with version 4.9.0 using 5.0.0 contracts?

Support Upgrades
1

I have an upgradable contract that uses OpenZeppelin version 4.9.0. This contract is deployed on Ethereum. OpenZeppelin version 5.0.0 has been released. My questions: Next time I upgrade the smart contract

  1. Could I use new v5 contracts ?
  2. Could I replace the v4 contracts with v5 contracts ?
  3. Will the OpenZeppelin upgrade plugin identify errors/conflicts if they exists?

The following code to reproduce is only an example (would probably not cause a problem because it is simple). But my question is more general about upgrades between different breaking changes versions of OpenZeppelin and the recommendation of the developers ?

Thank you

:1234: Code to reproduce

The code of the deployed upgradable contract

// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.9.0/contracts/token/ERC20/IERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.9.0/contracts/token/ERC20/utils/SafeERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v4.9.0/contracts/proxy/utils/Initializable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v4.9.0/contracts/proxy/utils/UUPSUpgradeable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v4.9.0/contracts/access/AccessControlUpgradeable.sol";

contract ExampleV1 is Initializable, UUPSUpgradeable, AccessControlUpgradeable {
  using SafeERC20 for IERC20;

  uint256 counter;

  constructor() {
      _disableInitializers();
  }

  function initialize(
    address admin
  ) public initializer {
    __UUPSUpgradeable_init();
    __AccessControl_init();
    _grantRole(DEFAULT_ADMIN_ROLE, admin);
  }

  function _authorizeUpgrade(
    address newContractAddress
  ) internal view override onlyRole(DEFAULT_ADMIN_ROLE) { }

  function doSomething() external {
    counter++;
  } 

  function getVersion() public pure returns (string memory) {
    return "Example Version 1";
  }
}

The new implementation contract that I would deploy and then set the proxy to:

// SPDX-License-Identifier: MIT
pragma solidity 0.8.20;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v5.0.0/contracts/token/ERC20/IERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v5.0.0/contracts/token/ERC20/utils/SafeERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v5.0.0/contracts/proxy/utils/Initializable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v5.0.0/contracts/proxy/utils/UUPSUpgradeable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v5.0.0/contracts/access/AccessControlUpgradeable.sol";

contract ExampleV2 is UUPSUpgradeable, AccessControlUpgradeable {
  using SafeERC20 for IERC20;

  uint256 public counter;

  function _authorizeUpgrade(
    address newContractAddress
  ) internal view override onlyRole(DEFAULT_ADMIN_ROLE) { }

  function doSomething() external {
    counter = counter + 2;
  } 

  function getVersion() public pure returns (string memory) {
    return "Example Version 2";
  }
}

:computer: Environment

Hardhat / Remix

2
  • Could I use new v5 contracts ?

It is not safe to upgrade an existing deployment from 4.x to 5.x. See Contract upgrade failed because variables are deleted in openzepplin 5.0 - #2 by ericglau

  • Could I replace the v4 contracts with v5 contracts ?

If you do replace them (note there are some differences in usage), the new contract can only be used for new proxy deployments. As above, you cannot upgrade an existing deployment to a different major version of OpenZeppelin Contracts.

  • Will the OpenZeppelin upgrade plugin identify errors/conflicts if they exists?

Conflicts will definitely exist across major version changes. The upgrades plugin will identify them, but you should not even attempt this kind of upgrade because it is known to be unsafe.

1 Like
3

@ericglau I wrote a small article about it https://medium.com/51nodes/why-upgrading-openzeppelin-smart-contracts-from-version-4-to-version-5-is-unsafe-e08be30efd8a

thanks for your help

1 Like