ERC20Votes: add a new extension of the ERC20 token with support for voting snapshots and delegation. (#2632)ERC20VotesComp: Variant of ERC20Votes that is compatible with Compound's Comp token interface but restricts supply to uint96. (#2706)ERC20Wrapper: add a new extension of the ERC20 token which wraps an underlying token. Deposit and withdraw guarantee that the total supply is backed by a corresponding amount of underlying token. (#2633)EnumerableSet and EnumerableMap.EnumerableSet and EnumerableMap.Counter: add a reset method. (#2678)unchecked blocks.Math: Add a ceilDiv method for performing ceiling division.ERC1155Supply: add a new ERC1155 extension that keeps track of the totalSupply of each tokenId. (#2593)BitMaps: add a new BitMaps library that provides a storage efficient datastructure for uint256 to bool mapping with contiguous keys. (#2710)### Breaking Changes
ERC20FlashMint is no longer a Draft ERC. (#2673))How to update: Change your import paths by removing the draft- prefix from @openzeppelin/contracts/token/ERC20/extensions/draft-ERC20FlashMint.sol.
IERC20Metadata: add a new extended interface that includes the optional name(), symbol() and decimals() functions. (#2561)ERC777: make reception acquirement optional in _mint. (#2552)ERC20Permit: add a _useNonce to enable further usage of ERC712 signatures. (#2565)ERC20FlashMint: add an implementation of the ERC3156 extension for flash-minting ERC20 tokens. (#2543)SignatureChecker: add a signature verification library that supports both EOA and ERC1271 compliant contracts as signers. (#2532)Multicall: add abstract contract with multicall(bytes[] calldata data) function to bundle multiple calls together (#2608)ECDSA: add support for ERC2098 short-signatures. (#2582)AccessControl: add a onlyRole modifier to restrict specific function to callers bearing a specific role. (#2609)StorageSlot: add a library for reading and writing primitive types to specific storage slots. (#2542)UUPSUpgradeable to implement the UUPS proxy pattern together with EIP1967Proxy. (#2542)This release includes two small breaking changes in TimelockController.
onlyRole modifier in this contract was designed to let anyone through if the role was granted to address(0),
allowing the possibility to to make a role "open", which can be used for EXECUTOR_ROLE. This modifier is now
replaced by AccessControl.onlyRole, which does not have this ability. The previous behavior was moved to the
modifier TimelockController.onlyRoleOrOpenRole.PROPOSER_ROLE an open role (as described in the previous item) if it was granted to
address(0). This would affect the schedule, scheduleBatch, and cancel operations in TimelockController.
This ability was removed as it does not make sense to open up the PROPOSER_ROLE in the same way that it does for
EXECUTOR_ROLE.Context: making _msgData return bytes calldata instead of bytes memory (#2492)ERC20: removed the _setDecimals function and the storage slot associated to decimals. (#2502)Strings: addition of a toHexString function. (#2504)EnumerableMap: change implementation to optimize for key → value lookups instead of enumeration. (#2518)GSN: deprecate GSNv1 support in favor of upcoming support for GSNv2. (#2521)ERC165: remove uses of storage in the base ERC165 implementation. ERC165 based contracts now use storage-less virtual functions. Old behavior remains available in the ERC165Storage extension. (#2505)Initializable: make initializer check stricter during construction. (#2531)ERC721: remove enumerability of tokens from the base implementation. This feature is now provided separately through the ERC721Enumerable extension. (#2511)AccessControl: removed enumerability by default for a more lightweight contract. It is now opt-in through AccessControlEnumerable. (#2512)ERC2771Context and a MinimalForwarder for meta-transactions. (#2508)ERC20Capped: optimize gas usage by enforcing the check directly in _mint. (#2524)UpgradeableProxy to ERC1967Proxy. (#2547)ERC777: optimize the gas costs of the constructor. (#2551)ERC721URIStorage: add a new extension that implements the _setTokenURI behavior as it was available in 3.4.0. (#2555)AccessControl: added ERC165 interface detection. (#2562)ERC1155: make uri public so overloading function can call it using super. (#2576)AccessControlEnumerable: Fixed renounceRole not updating enumerable set of addresses for a role. (#2572)Since this version has moved a few contracts to different directories, users upgrading from a previous version will need to adjust their import statements. To make this easier, the package includes a script that will migrate import statements automatically. After upgrading to the latest version of the package, run:
npx openzeppelin-contracts-migrate-imports
Make sure you're using git or another version control system to be able to recover from any potential error in our script.
Some further changes have been done between the different beta iterations. Transitions made during this period are configured in the migrate-imports script. Consequently, you can upgrade from any previous 4.0-beta.x version using the same script as described in the How to upgrade from 3.x section.
BeaconProxy: added new kind of proxy that allows simultaneous atomic upgrades. (#2411)EIP712: added helpers to verify EIP712 typed data signatures on chain. (#2418)ERC20Permit: added an implementation of the ERC20 permit extension for gasless token approvals. (#2237)ERC20PresetFixedSupply and ERC777PresetFixedSupply. (#2399)Address: added functionDelegateCall, similar to the existing functionCall. (#2333)Clones: added a library for deploying EIP 1167 minimal proxies. (#2449)Context: moved from contracts/GSN to contracts/utils. (#2453)PaymentSplitter: replace usage of .transfer() with Address.sendValue for improved compatibility with smart wallets. (#2455)UpgradeableProxy: bubble revert reasons from initialization calls. (#2454)SafeMath: fix a memory allocation issue by adding new SafeMath.tryOp(uint,uint)→(bool,uint) functions. SafeMath.op(uint,uint,string)→uint are now deprecated. (#2462)EnumerableMap: fix a memory allocation issue by adding new EnumerableMap.tryGet(uint)→(bool,address) functions. EnumerableMap.get(uint)→string is now deprecated. (#2462)ERC165Checker: added batch getSupportedInterfaces. (#2469)RefundEscrow: beneficiaryWithdraw will forward all available gas to the beneficiary. (#2480)ERC777: fix potential reentrancy issues for custom extensions to ERC777. (#2483)If you're using our implementation of ERC777 from version 3.3.0 or earlier, and you define a custom _beforeTokenTransfer function that writes to a storage variable, you may be vulnerable to a reentrancy attack. If you're affected and would like assistance please write to security@openzeppelin.com. Read more in the pull request.
solc-0.7 tag to compile without warnings.Address: added functionStaticCall, similar to the existing functionCall. (#2333)TimelockController: added a contract to augment access control schemes with a delay. (#2354)EnumerableSet: added Bytes32Set, for sets of bytes32. (#2395)ERC777: Remove a warning about function state visibility in Solidity 0.7. (#2327)Aside from upgrading them from Solidity 0.5 to 0.6, we've changed a few minor things from the proxy contracts as they were found in OpenZeppelin SDK.
UpgradeabilityProxy was renamed to UpgradeableProxy.AdminUpgradeabilityProxy was renamed to TransparentUpgradeableProxy.Proxy._willFallback was renamed to Proxy._beforeFallback.UpgradeabilityProxy._setImplementation and AdminUpgradeabilityProxy._setAdmin were made private.Address.isContract: switched from extcodehash to extcodesize for less gas usage. (#2311)ERC20Snapshot: switched to using _beforeTokenTransfer hook instead of overriding ERC20 operations. (#2312)This small change in the way we implemented ERC20Snapshot may affect users who are combining this contract with
other ERC20 flavors, since it no longer overrides _transfer, _mint, and _burn. This can result in having to remove Solidity override(...) specifiers in derived contracts for these functions, and to instead have to add it for _beforeTokenTransfer. See Using Hooks in the documentation.
SafeCast: added functions to downcast signed integers (e.g. toInt32), improving usability of SignedSafeMath. (#2243)functionCall: new helpers that replicate Solidity's function call semantics, reducing the need to rely on call. (#2264)ERC1155: added support for a base implementation, non-standard extensions and a preset contract. (#2014, #2230)ReentrancyGuard: reduced overhead of using the nonReentrant modifier. (#2171)AccessControl: added a RoleAdminChanged event to _setAdminRole. (#2214)public functions in the token preset contracts virtual. (#2257)SafeERC20: deprecated safeApprove. (#2268)ERC777: fixed the _approve internal function not validating some of their arguments for non-zero addresses. (#2213)AccessControl: new contract for managing permissions in a system, replacement for Ownable and Roles. (#2112)SafeCast: new functions to convert to and from signed and unsigned values: toUint256 and toInt256. (#2123)EnumerableMap: a new data structure for key-value pairs (like mapping) that can be iterated over. (#2160)ERC721: burn(owner, tokenId) was removed, use burn(tokenId) instead. (#2125)ERC721: _checkOnERC721Received was removed. (#2125)ERC721: _transferFrom and _safeTransferFrom were renamed to _transfer and _safeTransfer. (#2162)Ownable: removed _transferOwnership. (#2162)PullPayment, Escrow: withdrawWithGas was removed. The old withdraw function now forwards all gas. (#2125)Roles was removed, use AccessControl as a replacement. (#2112)ECDSA: when receiving an invalid signature, recover now reverts instead of returning the zero address. (#2114)Create2: added an amount argument to deploy for contracts with payable constructors. (#2117)Pausable: moved to the utils directory. (#2122)Strings: moved to the utils directory. (#2122)Counters: moved to the utils directory. (#2122)SignedSafeMath: moved to the math directory. (#2122)ERC20Snapshot: moved to the token/ERC20 directory. snapshot was changed into an internal function. (#2122)Ownable: moved to the access directory. (#2120)Ownable: removed isOwner. (#2120)Secondary: removed from the library, use Ownable instead. (#2120)Escrow, ConditionalEscrow, RefundEscrow: these now use Ownable instead of Secondary, their external API changed accordingly. (#2120)ERC20: removed _burnFrom. (#2119)Address: removed toPayable, use payable(address) instead. (#2133)ERC777: _send, _mint and _burn now use the caller as the operator. (#2134)ERC777: removed _callsTokensToSend and _callTokensReceived. (#2134)EnumerableSet: renamed get to at. (#2151)ERC165Checker: functions no longer have a leading underscore. (#2150)ERC721Metadata, ERC721Enumerable: these contracts were removed, and their functionality merged into ERC721. (#2160)ERC721: added a constructor for name and symbol. (#2160)ERC20Detailed: this contract was removed and its functionality merged into ERC20. (#2161)ERC20: added a constructor for name and symbol. decimals now defaults to 18. (#2161)Strings: renamed fromUint256 to toString (#2188)ERC777: fixed the _send and _approve internal functions not validating some of their arguments for non-zero addresses. (#2212)SafeCast.toUintXX: new library for integer downcasting, which allows for safe operation on smaller types (e.g. uint32) when combined with SafeMath. (#1926)ERC721Metadata: added baseURI, which can be used for dramatic gas savings when all token URIs share a prefix (e.g. http://api.myapp.com/tokens/<id>). (#1970)EnumerableSet: new library for storing enumerable sets of values. Only AddressSet is supported in this release. (#2061)Create2: simple library to make usage of the CREATE2 opcode easier. (#1744)ERC777: _burn is now internal, providing more flexibility and making it easier to create tokens that deflate. (#1908)ReentrancyGuard: greatly improved gas efficiency by using the net gas metering mechanism introduced in the Istanbul hardfork. (#1992, #1996)ERC777: improve extensibility by making _send and related functions internal. (#2027)ERC721: improved revert reason when transferring tokens to a non-recipient contract. (#2018)ERC165Checker now requires a minimum Solidity compiler version of 0.5.10. (#1829)Address.toPayable: added a helper to convert between address types without having to resort to low-level casting. (#1773)Address.sendValue: added a replacement to Solidity's transfer, removing the fixed gas stipend. (#1962)PullPayment.withdrawPaymentsWithGas(address payable payee)Escrow.withdrawWithGas(address payable payee)SafeMath: added support for custom error messages to sub, div and mod functions. (#1828)Address.isContract: switched from extcodesize to extcodehash for less gas usage. (#1802)ERC20 and ERC777 updated to throw custom errors on subtraction overflows. (#1828)PullPayment.withdrawPayments(address payable payee)Escrow.withdraw(address payable payee)Address now requires a minimum Solidity compiler version of 0.5.5. (#1802)SignatureBouncer has been removed from drafts, both to avoid confusions with the GSN and GSNRecipientSignature (previously called GSNBouncerSignature) and because the API was not very clear. (#1879)The final 2.4.0 release includes a refactor of the GSN contracts that will be a breaking change for 2.4.0-beta users.
_preRelayedCall and _postRelayedCall were removed and must now be explicitly implemented always in custom recipients. If your custom recipient didn't include an implementation, you can provide an empty one.GSNRecipient, GSNBouncerBase, and GSNContext were all merged into GSNRecipient.GSNBouncerSignature and GSNBouncerERC20Fee were renamed to GSNRecipientSignature and GSNRecipientERC20Fee.GSNRecipient when using GSNRecipientSignature and GSNRecipientERC20Fee.For example, a contract using GSNBouncerSignature would have to be changed in the following way.
-contract MyDapp is GSNRecipient, GSNBouncerSignature {
+contract MyDapp is GSNRecipientSignature {
Refer to the table below to adjust your inheritance list.
| 2.4.0-beta | 2.4.0 |
|---|---|
GSNRecipient, GSNBouncerSignature |
GSNRecipientSignature |
GSNRecipient, GSNBouncerERC20Fee |
GSNRecipientERC20Fee |
GSNBouncerBase |
GSNRecipient |
ERC1820: added support for interacting with the ERC1820 registry contract (IERC1820Registry), as well as base contracts that can be registered as implementers there. (#1677)ERC777: support for the ERC777 token, which has multiple improvements over ERC20 (but is backwards compatible with it) such as built-in burning, a more straightforward permission system, and optional sender and receiver hooks on transfer (mandatory for contracts!). (#1684)PostDeliveryCrowdsale: some validations where skipped when paired with other crowdsale flavors, such as AllowanceCrowdsale, or MintableCrowdsale and ERC20Capped, which could cause buyers to not be able to claim their purchased tokens. (#1721)ERC20._transfer: the from argument was allowed to be the zero address, so it was possible to internally trigger a transfer of 0 tokens from the zero address. This address is not a valid destinatary of transfers, nor can it give or receive allowance, so this behavior was inconsistent. It now reverts. (#1752)ERC20Snapshot: create snapshots on demand of the token balances and total supply, to later retrieve and e.g. calculate dividends at a past time. (#1617)SafeERC20: ERC20 contracts with no return value (i.e. that revert on failure) are now supported. (#1655)ERC20: added internal _approve(address owner, address spender, uint256 value), allowing derived contracts to set the allowance of arbitrary accounts. (#1609)ERC20Metadata: added internal _setTokenURI(string memory tokenURI). (#1618)TimedCrowdsale: added internal _extendTime(uint256 newClosingTime) as well as TimedCrowdsaleExtended(uint256 prevClosingTime, uint256 newClosingTime) event allowing to extend the crowdsale, as long as it hasn't already closed.ECDSA: recover no longer accepts malleable signatures (those using upper-range values for s, or 0/1 for v). (#1622)ERC721's transfers are now more gas efficient due to removal of unnecessary SafeMath calls. (#1610)SafeERC20: safeApprove wasn't properly checking for a zero allowance when attempting to set a non-zero allowance. (#1647)TokenMetadata has been renamed to ERC20Metadata. (#1618)Counter has been renamed to Counters and its API has been improved. See an example in ERC721, lines 17 and 204. (#1610)SafeERC20.safeApprove bugfix. (#1647)PublicRole.behavior.js, which may be useful to users testing their own Roles.WhitelistCrowdsale: a crowdsale where only whitelisted accounts (WhitelistedRole) can purchase tokens. Adding or removing accounts from the whitelist is done by whitelist admins (WhitelistAdminRole). Similar to the pre-2.0 WhitelistedCrowdsale. (#1525, #1589)RefundablePostDeliveryCrowdsale: replacement for RefundableCrowdsale (deprecated, see below) where tokens are only granted once the crowdsale ends (if it meets its goal). (#1543)PausableCrowdsale: allows for pausers (PauserRole) to pause token purchases. Other crowdsale operations (e.g. withdrawals and refunds, if applicable) are not affected. (#832)ERC20: transferFrom and _burnFrom now emit Approval events, to represent the token's state comprehensively through events. (#1524)ERC721: added _burn(uint256 tokenId), replacing the similar deprecated function (see below). (#1550)ERC721: added _tokensOfOwner(address owner), allowing to internally retrieve the array of an account's owned tokens. (#1522)public, meaning it is not necessary to extend these contracts in order to deploy them. The exception is FinalizableCrowdsale, since it is meaningless unless extended. (#1564)SignedSafeMath: added overflow-safe operations for signed integers (int256). (#1559, #1588)Array was behind the rest of the libray so it was updated to v0.4.24. (#1553)ERC20: more gas efficient due to removed redundant requires. (#1409)ERC721: fixed a bug that prevented internal data structures from being properly cleaned, missing potential gas refunds. (#1539 and #1549)ERC721: general gas savings on transferFrom, _mint and _burn, due to redudant requires and SSTOREs. (#1549)