Hi @cjd9s ,
You may want to look at the proxy contracts that were migrated to OpenZeppelin Contracts 3.x which could be simpler to follow the hierarchy:
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
import "./UpgradeableProxy.sol";
/**
* @dev This contract implements a proxy that is upgradeable by an admin.
*
* To avoid https://medium.com/nomic-labs-blog/malicious-backdoors-in-ethereum-proxies-62629adf3357[proxy selector
* clashing], which can potentially be used in an attack, this contract uses the
* https://blog.openzeppelin.com/the-transparent-proxy-pattern/[transparent proxy pattern]. This pattern implies two
* things that go hand in hand:
*
* 1. If any account other than the admin calls the proxy, the call will be forwarded to the implementation, even if
* that call matches one of the admin functions exposed by the proxy itself.
* 2. If the admin calls the proxy, it can access the admin functions, but its calls will never be forwarded to the
* implementation. If the admin tries to call a function on the implementation it will fail with an error that says
* "admin cannot fallback to proxy target".
*
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Currently the OpenZeppelin Upgrades Plugins use contracts in Upgrades Core (though this will change to use the proxy contracts in OpenZeppelin Contracts). So recommend studying these versions as this is what you would use when deploying an upgradeable project today with the Upgrades Plugins.
The proxy contracts used in the OpenZeppelin CLI, as you found, have a more complex hierarchy.Building for interoperability: why we’re focusing on Upgrades Plugins as we are focusing our upgradeability efforts on the Upgrades Plugins exclusively.https://github.com/OpenZeppelin/openzeppelin-sdk/tree/v2.8.2/packages/lib/contracts/upgradeability
cjd9s:
The BaseAdminUpgradeabilityProxy contract inherits the BaseUpgradeabilityProxy contract, but only imports the UpgradeabilityProxy.sol file. Why does this work? Does this work because the UpgradeabilityProxy contract imports and inherits the BaseUpgradeabilityProxy? Why wouldn’t you just import the BaseUpgradeabilityProxy contract into the BaseAdminUpgradeabilityProxy contract?
I assume this works because an import of a parent allows inheriting from a grand parent.
I assume the same applies.
I assume that super calls up the inheritance tree: https://solidity.readthedocs.io/en/latest/contracts.html#inheritance
I suggest trying it out with some simple contracts to see it for yourself.