Merge branch 'master' into refactor/virtualERC165

.github/workflows/test.yml

@@ -26,11 +26,18 @@ jobs:
         if: steps.cache.outputs.cache-hit != 'true'
       - run: npm run lint
       - run: npm run test
+        env:
+          FORCE_COLOR: 1
+          ENABLE_GAS_REPORT: 1
+      - name: Print gas report
+        run: cat gas-report.txt
 
   coverage:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
       - uses: actions/setup-node@v2
         with:
           node-version: 10.x

CHANGELOG.md

@@ -2,8 +2,10 @@
 
 ## Unreleased
 
-* Now targeting the 0.8.x line of Solidity compilers. For 0.6.x (resp 0.7.x) support, use version 3.4.0 (resp 3.4.0-solc-0.7) of OpenZeppelin.
-* `Context`: making `_msgData` return `bytes calldata` instead of `bytes memory` ([#2492](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2492))
+ * Now targeting the 0.8.x line of Solidity compilers. For 0.6.x (resp 0.7.x) support, use version 3.4.0 (resp 3.4.0-solc-0.7) of OpenZeppelin.
+ * `Context`: making `_msgData` return `bytes calldata` instead of `bytes memory` ([#2492](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2492))
+ * `ERC20`: Removed the `_setDecimals` function and the storage slot associated to decimals. ([#2502](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2502))
+ * `Strings`: addition of a `toHexString` function.  ([#2504](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2504))
 
 ## 3.4.0 (2021-02-02)
 

contracts/mocks/ERC20DecimalsMock.sol

@@ -5,7 +5,13 @@ pragma solidity ^0.8.0;
 import "../token/ERC20/ERC20.sol";
 
 contract ERC20DecimalsMock is ERC20 {
-    constructor (string memory name, string memory symbol, uint8 decimals) ERC20(name, symbol) {
-        _setupDecimals(decimals);
+    uint8 immutable private _decimals;
+
+    constructor (string memory name_, string memory symbol_, uint8 decimals_) ERC20(name_, symbol_) {
+        _decimals = decimals_;
+    }
+
+    function decimals() public view virtual override returns (uint8) {
+        return _decimals;
     }
 }

contracts/mocks/StringsMock.sol

@@ -8,4 +8,10 @@ contract StringsMock {
     function fromUint256(uint256 value) public pure returns (string memory) {
         return Strings.toString(value);
     }
+    function fromUint256Hex(uint256 value) public pure returns (string memory) {
+        return Strings.toHexString(value);
+    }
+    function fromUint256HexFixed(uint256 value, uint256 length) public pure returns (string memory) {
+        return Strings.toHexString(value, length);
+    }
 }

contracts/token/ERC1155/ERC1155.sol

@@ -140,8 +140,9 @@ contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI {
 
         _beforeTokenTransfer(operator, from, to, _asSingletonArray(id), _asSingletonArray(amount), data);
 
-        require(_balances[id][from] >= amount, "ERC1155: insufficient balance for transfer");
-        _balances[id][from] -= amount;
+        uint256 fromBalance = _balances[id][from];
+        require(fromBalance >= amount, "ERC1155: insufficient balance for transfer");
+        _balances[id][from] = fromBalance - amount;
         _balances[id][to] += amount;
 
         emit TransferSingle(operator, from, to, id, amount);
@@ -178,8 +179,9 @@ contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI {
             uint256 id = ids[i];
             uint256 amount = amounts[i];
 
-            require(_balances[id][from] >= amount, "ERC1155: insufficient balance for transfer");
-            _balances[id][from] -= amount;
+            uint256 fromBalance = _balances[id][from];
+            require(fromBalance >= amount, "ERC1155: insufficient balance for transfer");
+            _balances[id][from] = fromBalance - amount;
             _balances[id][to] += amount;
         }
 
@@ -276,8 +278,9 @@ contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI {
 
         _beforeTokenTransfer(operator, account, address(0), _asSingletonArray(id), _asSingletonArray(amount), "");
 
-        require(_balances[id][account] >= amount, "ERC1155: burn amount exceeds balance");
-        _balances[id][account] -= amount;
+        uint256 accountBalance = _balances[id][account];
+        require(accountBalance >= amount, "ERC1155: burn amount exceeds balance");
+        _balances[id][account] = accountBalance - amount;
 
         emit TransferSingle(operator, account, address(0), id, amount);
     }
@@ -301,8 +304,9 @@ contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI {
             uint256 id = ids[i];
             uint256 amount = amounts[i];
 
-            require(_balances[id][account] >= amount, "ERC1155: burn amount exceeds balance");
-            _balances[id][account] -= amount;
+            uint256 accountBalance = _balances[id][account];
+            require(accountBalance >= amount, "ERC1155: burn amount exceeds balance");
+            _balances[id][account] = accountBalance - amount;
         }
 
         emit TransferBatch(operator, account, address(0), ids, amounts);

contracts/token/ERC20/ERC20.sol

@@ -38,21 +38,19 @@ contract ERC20 is Context, IERC20 {
 
     string private _name;
     string private _symbol;
-    uint8 private _decimals;
 
     /**
-     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
-     * a default value of 18.
+     * @dev Sets the values for {name} and {symbol}.
      *
-     * To select a different value for {decimals}, use {_setupDecimals}.
+     * The defaut value of {decimals} is 18. To select a different value for
+     * {decimals} you should overload it.
      *
      * All three of these values are immutable: they can only be set once during
      * construction.
      */
     constructor (string memory name_, string memory symbol_) {
         _name = name_;
         _symbol = symbol_;
-        _decimals = 18;
     }
 
     /**
@@ -76,15 +74,15 @@ contract ERC20 is Context, IERC20 {
      * be displayed to a user as `5,05` (`505 / 10 ** 2`).
      *
      * Tokens usually opt for a value of 18, imitating the relationship between
-     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
-     * called.
+     * Ether and Wei. This is the value {ERC20} uses, unless this function is
+     * overloaded;
      *
      * NOTE: This information is only used for _display_ purposes: it in
      * no way affects any of the arithmetic of the contract, including
      * {IERC20-balanceOf} and {IERC20-transfer}.
      */
     function decimals() public view virtual returns (uint8) {
-        return _decimals;
+        return 18;
     }
 
     /**
@@ -149,8 +147,9 @@ contract ERC20 is Context, IERC20 {
     function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
         _transfer(sender, recipient, amount);
 
-        require(_allowances[sender][_msgSender()] >= amount, "ERC20: transfer amount exceeds allowance");
-        _approve(sender, _msgSender(), _allowances[sender][_msgSender()] - amount);
+        uint256 currentAllowance = _allowances[sender][_msgSender()];
+        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
+        _approve(sender, _msgSender(), currentAllowance - amount);
 
         return true;
     }
@@ -187,8 +186,9 @@ contract ERC20 is Context, IERC20 {
      * `subtractedValue`.
      */
     function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
-        require(_allowances[_msgSender()][spender] >= subtractedValue, "ERC20: decreased allowance below zero");
-        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] - subtractedValue);
+        uint256 currentAllowance = _allowances[_msgSender()][spender];
+        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
+        _approve(_msgSender(), spender, currentAllowance - subtractedValue);
 
         return true;
     }
@@ -213,8 +213,9 @@ contract ERC20 is Context, IERC20 {
 
         _beforeTokenTransfer(sender, recipient, amount);
 
-        require(_balances[sender] >= amount, "ERC20: transfer amount exceeds balance");
-        _balances[sender] -= amount;
+        uint256 senderBalance = _balances[sender];
+        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
+        _balances[sender] = senderBalance - amount;
         _balances[recipient] += amount;
 
         emit Transfer(sender, recipient, amount);
@@ -255,8 +256,9 @@ contract ERC20 is Context, IERC20 {
 
         _beforeTokenTransfer(account, address(0), amount);
 
-        require(_balances[account] >= amount, "ERC20: burn amount exceeds balance");
-        _balances[account] -= amount;
+        uint256 accountBalance = _balances[account];
+        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
+        _balances[account] = accountBalance - amount;
         _totalSupply -= amount;
 
         emit Transfer(account, address(0), amount);
@@ -283,17 +285,6 @@ contract ERC20 is Context, IERC20 {
         emit Approval(owner, spender, amount);
     }
 
-    /**
-     * @dev Sets {decimals} to a value other than the default one of 18.
-     *
-     * WARNING: This function should only be called from the constructor. Most
-     * applications that interact with token contracts will not expect
-     * {decimals} to ever change, and may work incorrectly if it does.
-     */
-    function _setupDecimals(uint8 decimals_) internal virtual {
-        _decimals = decimals_;
-    }
-
     /**
      * @dev Hook that is called before any transfer of tokens. This includes
      * minting and burning.

contracts/token/ERC20/ERC20Burnable.sol

@@ -32,8 +32,9 @@ abstract contract ERC20Burnable is Context, ERC20 {
      * `amount`.
      */
     function burnFrom(address account, uint256 amount) public virtual {
-        require(allowance(account, _msgSender()) >= amount, "ERC20: burn amount exceeds allowance");
-        _approve(account, _msgSender(), allowance(account, _msgSender()) - amount);
+        uint256 currentAllowance = allowance(account, _msgSender());
+        require(currentAllowance >= amount, "ERC20: burn amount exceeds allowance");
+        _approve(account, _msgSender(), currentAllowance - amount);
         _burn(account, amount);
     }
 }

contracts/token/ERC777/ERC777.sol

@@ -278,8 +278,9 @@ contract ERC777 is Context, IERC777, IERC20 {
 
         _move(spender, holder, recipient, amount, "", "");
 
-        require(_allowances[holder][spender] >= amount, "ERC777: transfer amount exceeds allowance");
-        _approve(holder, spender, _allowances[holder][spender] - amount);
+        uint256 currentAllowance = _allowances[holder][spender];
+        require(currentAllowance >= amount, "ERC777: transfer amount exceeds allowance");
+        _approve(holder, spender, currentAllowance - amount);
 
         _callTokensReceived(spender, holder, recipient, amount, "", "", false);
 
@@ -385,8 +386,9 @@ contract ERC777 is Context, IERC777, IERC20 {
         _beforeTokenTransfer(operator, from, address(0), amount);
 
         // Update state variables
-        require(_balances[from] >= amount, "ERC777: burn amount exceeds balance");
-        _balances[from] -= amount;
+        uint256 fromBalance = _balances[from];
+        require(fromBalance >= amount, "ERC777: burn amount exceeds balance");
+        _balances[from] = fromBalance - amount;
         _totalSupply -= amount;
 
         emit Burned(operator, from, amount, data, operatorData);
@@ -405,8 +407,9 @@ contract ERC777 is Context, IERC777, IERC20 {
     {
         _beforeTokenTransfer(operator, from, to, amount);
 
-        require(_balances[from] >= amount, "ERC777: transfer amount exceeds balance");
-        _balances[from] -= amount;
+        uint256 fromBalance = _balances[from];
+        require(fromBalance >= amount, "ERC777: transfer amount exceeds balance");
+        _balances[from] = fromBalance - amount;
         _balances[to] += amount;
 
         emit Sent(operator, from, to, amount, userData, operatorData);

contracts/utils/Counters.sol

@@ -23,10 +23,16 @@ library Counters {
     }
 
     function increment(Counter storage counter) internal {
-        counter._value += 1;
+        unchecked {
+            counter._value += 1;
+        }
     }
 
     function decrement(Counter storage counter) internal {
-        counter._value = counter._value - 1;
+        uint256 value = counter._value;
+        require(value > 0, "Counter: decrement overflow");
+        unchecked {
+            counter._value = value - 1;
+        }
     }
 }

contracts/utils/Strings.sol

@@ -6,8 +6,10 @@ pragma solidity ^0.8.0;
  * @dev String operations.
  */
 library Strings {
+    bytes16 private constant alphabet = "0123456789abcdef";
+
     /**
-     * @dev Converts a `uint256` to its ASCII `string` representation.
+     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
      */
     function toString(uint256 value) internal pure returns (string memory) {
         // Inspired by OraclizeAPI's implementation - MIT licence
@@ -23,12 +25,43 @@ library Strings {
             temp /= 10;
         }
         bytes memory buffer = new bytes(digits);
-        uint256 index = digits;
-        temp = value;
+        while (value != 0) {
+            digits -= 1;
+            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
+            value /= 10;
+        }
+        return string(buffer);
+    }
+
+    /**
+     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
+     */
+    function toHexString(uint256 value) internal pure returns (string memory) {
+        if (value == 0) {
+            return "0x00";
+        }
+        uint256 temp = value;
+        uint256 length = 0;
         while (temp != 0) {
-            buffer[--index] = bytes1(uint8(48 + uint256(temp % 10)));
-            temp /= 10;
+            length++;
+            temp >>= 8;
+        }
+        return toHexString(value, length);
+    }
+
+    /**
+     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
+     */
+    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
+        bytes memory buffer = new bytes(2 * length + 2);
+        buffer[0] = "0";
+        buffer[1] = "x";
+        for (uint256 i = 2 * length + 1; i > 1; --i) {
+            buffer[i] = alphabet[value & 0xf];
+            value >>= 4;
         }
+        require(value == 0, "Strings: hex length insufficient");
         return string(buffer);
     }
+
 }

hardhat.config.js

@@ -4,25 +4,35 @@ const path = require('path');
 require('@nomiclabs/hardhat-truffle5');
 require('@nomiclabs/hardhat-solhint');
 require('solidity-coverage');
+require('hardhat-gas-reporter');
 
 for (const f of fs.readdirSync(path.join(__dirname, 'hardhat'))) {
   require(path.join(__dirname, 'hardhat', f));
 }
 
+const enableGasReport = !!process.env.ENABLE_GAS_REPORT;
+
 /**
  * @type import('hardhat/config').HardhatUserConfig
  */
 module.exports = {
-  solidity: '0.8.0',
-  settings: {
-    optimizer: {
-      enabled: false,
-      runs: 200,
+  solidity: {
+    version: '0.8.0',
+    settings: {
+      optimizer: {
+        enabled: enableGasReport,
+        runs: 200,
+      },
     },
   },
   networks: {
     hardhat: {
       blockGasLimit: 10000000,
     },
   },
+  gasReporter: {
+    enable: enableGasReport,
+    currency: 'USD',
+    outputFile: process.env.CI ? 'gas-report.txt' : undefined,
+  },
 };