Add clear function to Enumerable{Set,Map}

.changeset/sixty-tips-wink.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`EnumerableSet`: Add `clear` function to EnumerableSets which deletes all items in the set.

contracts/utils/structs/EnumerableSet.sol

@@ -4,6 +4,8 @@
 
 pragma solidity ^0.8.20;
 
+import {Arrays} from "../Arrays.sol";
+
 /**
  * @dev Library for managing
  * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
@@ -13,7 +15,7 @@ pragma solidity ^0.8.20;
  *
  * - Elements are added, removed, and checked for existence in constant time
  * (O(1)).
- * - Elements are enumerated in O(n). No guarantees are made on the ordering.
+ * - Elements are enumerated and cleared in O(n). No guarantees are made on the ordering.
  *
  * ```solidity
  * contract Example {
@@ -114,6 +116,20 @@ library EnumerableSet {
         }
     }
 
+    /**
+     * @dev Removes all the values from a set. O(n).
+     *
+     * WARNING: Developers should keep in mind that this function has an unbounded cost and using it may render the
+     * function uncallable if the set grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function _clear(Set storage set) private {
+        uint256 len = _length(set);
+        for (uint256 i = 0; i < len; ++i) {
+            delete set._positions[set._values[i]];
+        }
+        Arrays.unsafeSetLength(set._values, 0);
+    }
+
     /**
      * @dev Returns true if the value is in the set. O(1).
      */
@@ -180,6 +196,16 @@ library EnumerableSet {
         return _remove(set._inner, value);
     }
 
+    /**
+     * @dev Removes all the values from a set. O(n).
+     *
+     * WARNING: Developers should keep in mind that this function has an unbounded cost and using it may render the
+     * function uncallable if the set grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(Bytes32Set storage set) internal {
+        _clear(set._inner);
+    }
+
     /**
      * @dev Returns true if the value is in the set. O(1).
      */
@@ -253,6 +279,16 @@ library EnumerableSet {
         return _remove(set._inner, bytes32(uint256(uint160(value))));
     }
 
+    /**
+     * @dev Removes all the values from a set. O(n).
+     *
+     * WARNING: Developers should keep in mind that this function has an unbounded cost and using it may render the
+     * function uncallable if the set grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(AddressSet storage set) internal {
+        _clear(set._inner);
+    }
+
     /**
      * @dev Returns true if the value is in the set. O(1).
      */
@@ -326,6 +362,16 @@ library EnumerableSet {
         return _remove(set._inner, bytes32(value));
     }
 
+    /**
+     * @dev Removes all the values from a set. O(n).
+     *
+     * WARNING: Developers should keep in mind that this function has an unbounded cost and using it may render the
+     * function uncallable if the set grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(UintSet storage set) internal {
+        _clear(set._inner);
+    }
+
     /**
      * @dev Returns true if the value is in the set. O(1).
      */

scripts/generate/templates/EnumerableSet.js

@@ -5,6 +5,8 @@ const { TYPES } = require('./EnumerableSet.opts');
 const header = `\
 pragma solidity ^0.8.20;
 
+import {Arrays} from "../Arrays.sol";
+
 /**
  * @dev Library for managing
  * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
@@ -14,7 +16,7 @@ pragma solidity ^0.8.20;
  *
  * - Elements are added, removed, and checked for existence in constant time
  * (O(1)).
- * - Elements are enumerated in O(n). No guarantees are made on the ordering.
+ * - Elements are enumerated and cleared in O(n). No guarantees are made on the ordering.
  *
  * \`\`\`solidity
  * contract Example {
@@ -117,6 +119,20 @@ function _remove(Set storage set, bytes32 value) private returns (bool) {
     }
 }
 
+/**
+ * @dev Removes all the values from a set. O(n).
+ *
+ * WARNING: Developers should keep in mind that this function has an unbounded cost and using it may render the
+ * function uncallable if the set grows to the point where clearing it consumes too much gas to fit in a block.
+ */
+function _clear(Set storage set) private {
+    uint256 len = _length(set);
+    for (uint256 i = 0; i < len; ++i) {
+        delete set._positions[set._values[i]];
+    }
+    Arrays.unsafeSetLength(set._values, 0);
+}
+
 /**
  * @dev Returns true if the value is in the set. O(1).
  */
@@ -185,6 +201,16 @@ function remove(${name} storage set, ${type} value) internal returns (bool) {
     return _remove(set._inner, ${toBytes32(type, 'value')});
 }
 
+/**
+ * @dev Removes all the values from a set. O(n).
+ *
+ * WARNING: Developers should keep in mind that this function has an unbounded cost and using it may render the
+ * function uncallable if the set grows to the point where clearing it consumes too much gas to fit in a block.
+ */
+function clear(${name} storage set) internal {
+    _clear(set._inner);
+}
+
 /**
  * @dev Returns true if the value is in the set. O(1).
  */

test/utils/structs/EnumerableSet.behavior.js

@@ -109,6 +109,41 @@ function shouldBehaveLikeSet() {
       expect(await this.methods.contains(this.valueB)).to.be.false;
     });
   });
+
+  describe('clear', function () {
+    it('clears a single item', async function () {
+      await this.methods.add(this.valueA);
+      await expect(this.methods.length()).to.eventually.equal(1);
+
+      await this.methods.clear();
+
+      await expect(this.methods.length()).to.eventually.equal(0);
+    });
+
+    it('clears multiple items', async function () {
+      await this.methods.add(this.valueA);
+      await this.methods.add(this.valueB);
+      await this.methods.add(this.valueC);
+      await expect(this.methods.length()).to.eventually.equal(3);
+
+      await this.methods.clear();
+
+      await expect(this.methods.length()).to.eventually.equal(0);
+    });
+
+    it('does not revert on empty set', async function () {
+      await this.methods.clear();
+    });
+
+    it('clear then add value', async function () {
+      await this.methods.add(this.valueA);
+      await this.methods.add(this.valueB);
+      await this.methods.clear();
+
+      await this.methods.add(this.valueA);
+      await expectMembersMatch(this.methods, [this.valueA]);
+    });
+  });
 }
 
 module.exports = {

test/utils/structs/EnumerableSet.test.js

@@ -27,6 +27,7 @@ async function fixture() {
         methods: getMethods(mock, {
           add: `$add(uint256,${type})`,
           remove: `$remove(uint256,${type})`,
+          clear: `$clear_EnumerableSet_${name}(uint256)`,
           contains: `$contains(uint256,${type})`,
           length: `$length_EnumerableSet_${name}(uint256)`,
           at: `$at_EnumerableSet_${name}(uint256,uint256)`,