Add a _spendAllowance function to ERC20 & ERC777 (#3170)

(cherry picked from commit c5a6cae898)

CHANGELOG.md

@@ -14,7 +14,10 @@
  * `Base64`: add a library to parse bytes into base64 strings using `encode(bytes memory)` function, and provide examples to show how to use to build URL-safe `tokenURIs`. ([#2884](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2884))
  * `ERC20`: reduce allowance before triggering transfer. ([#3056](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3056))
  * `ERC20`: do not update allowance on `transferFrom` when allowance is `type(uint256).max`. ([#3085](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3085))
+ * `ERC20`: add a `_spendAllowance` internal function. ([#3170](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3170))
+ * `ERC20Burnable`: do not update allowance on `burnFrom` when allowance is `type(uint256).max`. ([#3170](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3170))
  * `ERC777`: do not update allowance on `transferFrom` when allowance is `type(uint256).max`. ([#3085](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3085))
+ * `ERC777`: add a `_spendAllowance` internal function. ([#3170](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3170))
  * `SignedMath`: a new signed version of the Math library with `max`, `min`,  and `average`. ([#2686](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2686))
  * `SignedMath`: add a `abs(int256)` method that returns the unsigned absolute value of a signed value. ([#2984](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2984))
  * `ERC1967Upgrade`: Refactor the secure upgrade to use `ERC1822` instead of the previous rollback mechanism. This reduces code complexity and attack surface with similar security guarantees. ([#3021](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3021))

contracts/token/ERC20/ERC20.sol

@@ -161,16 +161,8 @@ contract ERC20 is Context, IERC20, IERC20Metadata {
         uint256 amount
     ) public virtual override returns (bool) {
         address spender = _msgSender();
-        uint256 currentAllowance = allowance(from, spender);
-        if (currentAllowance != type(uint256).max) {
-            require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
-            unchecked {
-                _approve(from, spender, currentAllowance - amount);
-            }
-        }
-
+        _spendAllowance(from, spender, amount);
         _transfer(from, to, amount);
-
         return true;
     }
 
@@ -327,6 +319,28 @@ contract ERC20 is Context, IERC20, IERC20Metadata {
         emit Approval(owner, spender, amount);
     }
 
+    /**
+     * @dev Spend `amount` form the allowance of `owner` toward `spender`.
+     *
+     * Does not update the allowance amount in case of infinite allowance.
+     * Revert if not enough allowance is available.
+     *
+     * Might emit an {Approval} event.
+     */
+    function _spendAllowance(
+        address owner,
+        address spender,
+        uint256 amount
+    ) internal virtual {
+        uint256 currentAllowance = allowance(owner, spender);
+        if (currentAllowance != type(uint256).max) {
+            require(currentAllowance >= amount, "ERC20: insufficient allowance");
+            unchecked {
+                _approve(owner, spender, currentAllowance - amount);
+            }
+        }
+    }
+
     /**
      * @dev Hook that is called before any transfer of tokens. This includes
      * minting and burning.

contracts/token/ERC20/extensions/ERC20Burnable.sol

@@ -33,11 +33,7 @@ abstract contract ERC20Burnable is Context, ERC20 {
      * `amount`.
      */
     function burnFrom(address account, uint256 amount) public virtual {
-        uint256 currentAllowance = allowance(account, _msgSender());
-        require(currentAllowance >= amount, "ERC20: burn amount exceeds allowance");
-        unchecked {
-            _approve(account, _msgSender(), currentAllowance - amount);
-        }
+        _spendAllowance(account, _msgSender(), amount);
         _burn(account, amount);
     }
 }

contracts/token/ERC777/ERC777.sol

@@ -293,13 +293,7 @@ contract ERC777 is Context, IERC777, IERC20 {
 
         _callTokensToSend(spender, holder, recipient, amount, "", "");
 
-        uint256 currentAllowance = _allowances[holder][spender];
-        if (currentAllowance != type(uint256).max) {
-            require(currentAllowance >= amount, "ERC777: transfer amount exceeds allowance");
-            unchecked {
-                _approve(holder, spender, currentAllowance - amount);
-            }
-        }
+        _spendAllowance(holder, spender, amount);
 
         _move(spender, holder, recipient, amount, "", "");
 
@@ -526,6 +520,28 @@ contract ERC777 is Context, IERC777, IERC20 {
         }
     }
 
+    /**
+     * @dev Spend `amount` form the allowance of `owner` toward `spender`.
+     *
+     * Does not update the allowance amount in case of infinite allowance.
+     * Revert if not enough allowance is available.
+     *
+     * Might emit an {Approval} event.
+     */
+    function _spendAllowance(
+        address owner,
+        address spender,
+        uint256 amount
+    ) internal virtual {
+        uint256 currentAllowance = allowance(owner, spender);
+        if (currentAllowance != type(uint256).max) {
+            require(currentAllowance >= amount, "ERC777: insufficient allowance");
+            unchecked {
+                _approve(owner, spender, currentAllowance - amount);
+            }
+        }
+    }
+
     /**
      * @dev Hook that is called before any token transfer. This includes
      * calls to {send}, {transfer}, {operatorSend}, minting and burning.

test/token/ERC20/ERC20.behavior.js

@@ -108,7 +108,7 @@ function shouldBehaveLikeERC20 (errorPrefix, initialSupply, initialHolder, recip
             it('reverts', async function () {
               await expectRevert(
                 this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
-                `${errorPrefix}: transfer amount exceeds allowance`,
+                `${errorPrefix}: insufficient allowance`,
               );
             });
           });

test/token/ERC20/extensions/ERC20Burnable.behavior.js

@@ -98,7 +98,7 @@ function shouldBehaveLikeERC20Burnable (owner, initialBalance, [burner]) {
       it('reverts', async function () {
         await this.token.approve(burner, allowance, { from: owner });
         await expectRevert(this.token.burnFrom(owner, allowance.addn(1), { from: burner }),
-          'ERC20: burn amount exceeds allowance',
+          'ERC20: insufficient allowance',
         );
       });
     });

test/token/ERC20/extensions/ERC20Wrapper.test.js

@@ -59,7 +59,7 @@ contract('ERC20', function (accounts) {
     it('missing approval', async function () {
       await expectRevert(
         this.token.depositFor(initialHolder, initialSupply, { from: initialHolder }),
-        'ERC20: transfer amount exceeds allowance',
+        'ERC20: insufficient allowance',
       );
     });