Enable address(0) erc20 balances to match ethscription behavior

[RogerPodacter]

Note

Introduce an upgradeable ERC20 base that allows address(0) balances and migrate EthscriptionsERC20 to use it, enabling mint/transfer to the null address with updated tests and interface paths.

• Contracts:
  • ERC20NullOwnerCappedUpgradeable (new): Upgradeable ERC20 with cap and storage layout that treats address(0) as a valid holder; includes maxSupply().
  • EthscriptionsERC20: Refactored to extend ERC20NullOwnerCappedUpgradeable; TokenManager-only mint and forceTransfer now allow to/from == address(0) via _update; disables user transfers/approvals; exposes maxSupply() instead of cap().
  • TokenManager/Ethscriptions/CollectionsManager/EthscriptionERC721: Update imports to interfaces/IProtocolHandler and local paths; align with null-owner ERC20 behavior.
• Tests:
  • Replace cap() assertions with maxSupply(); add tests for minting to and transferring NFTs into address(0) reflecting in ERC20 balances; adjust imports.

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[Copilot]

Pull Request Overview

This pull request enables ERC-20 tokens to have balances at the zero address (address(0)) to match Ethscription behavior, where tokens can be held by the null address.

Key changes:

• Creates a new ERC20 implementation that allows null address ownership
• Updates token interface from cap() to maxSupply() for consistency
• Adds comprehensive test coverage for null address token operations

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
contracts/src/ERC20NullOwnerCappedUpgradeable.sol	New ERC20 implementation that supports null address ownership by overriding the _update function to credit rather than burn tokens sent to address(0)
contracts/src/EthscriptionsERC20.sol	Refactored to use the new null-owner-aware base contract and simplified token management functions
contracts/test/EthscriptionsToken.t.sol	Added tests for null address minting and transfers, plus updated existing test to use new maxSupply() method

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[Copilot]

The mint function bypasses the standard _mint helper function which handles minting logic. Consider using _mint(to, amount) instead of directly calling _update(address(0), to, amount) for consistency with ERC20 patterns and to ensure any future mint-specific logic is preserved.

Suggested change

	_update(address(0), to, amount);
	_mint(to, amount);

[Copilot]

The storage location calculation comment should be verified. The actual hash calculation should match the provided constant value to ensure storage slot uniqueness and prevent collisions with other contracts.

Suggested change

	bytes32 private constant STORAGE_LOCATION = 0x8f4f7bb0f9a741a04db8c5a3930ef1872dc1b0c6f996f78adc3f57e5f8b78400;
	function _getS() private pure returns (TokenStorage storage $) {
	assembly {
	$.slot := STORAGE_LOCATION
	// Compute storage slot as described in the comment above
	function _storageLocation() internal pure returns (bytes32) {
	// keccak256(abi.encode(uint256(keccak256("ethscriptions.storage.ERC20NullOwnerCapped")) - 1)) & ~bytes32(uint256(0xff))
	bytes32 typeHash = keccak256("ethscriptions.storage.ERC20NullOwnerCapped");
	uint256 slot = uint256(keccak256(abi.encode(uint256(typeHash) - 1))) & ~uint256(0xff);
	return bytes32(slot);
	}
	function _getS() private pure returns (TokenStorage storage $) {
	bytes32 location = _storageLocation();
	assembly {
	$.slot := location

[Copilot]

The _mint function is defined but not used in the codebase where mint directly calls _update. This creates inconsistency - either use _mint in the public mint function or remove this unused helper to avoid confusion.

Suggested change

	// Mint (null-owner aware)
	function _mint(address account, uint256 value) internal {
	_update(address(0), account, value);
	}

[Copilot]

Pull Request Overview

Copilot reviewed 9 out of 10 changed files in this pull request and generated 2 comments.

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[Copilot]

The _update function doesn't handle the case where from is address(0) (minting scenario). When minting, from should be address(0) and the balance check will fail since address(0) has no balance to debit. This function should handle minting by checking if from == address(0) and only updating totalSupply and crediting to in that case.

Suggested change

	// Debit from
	uint256 fromBalance = $.balances[from];
	if (fromBalance < value) {
	revert ERC20InsufficientBalance(from, fromBalance, value);
	}
	unchecked {
	$.balances[from] = fromBalance - value;
	}
	// Credit to
	unchecked {
	$.balances[to] += value;
	}
	if (from == address(0)) {
	// Minting: only credit 'to'
	unchecked {
	$.balances[to] += value;
	}
	} else {
	// Debit from
	uint256 fromBalance = $.balances[from];
	if (fromBalance < value) {
	revert ERC20InsufficientBalance(from, fromBalance, value);
	}
	unchecked {
	$.balances[from] = fromBalance - value;
	}
	// Credit to
	unchecked {
	$.balances[to] += value;
	}
	}

[Copilot]

The _mint function bypasses the _update function and directly manipulates balances and totalSupply. This creates inconsistency since _update is meant to be the single point for balance changes. The _mint function should call _update(address(0), account, value) after checking the cap, but _update needs to be fixed first to handle the minting case.