Add clear function to Enumerable{Set,Map} (#5486)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

contracts/utils/structs/EnumerableMap.sol

@@ -16,6 +16,7 @@ import {EnumerableSet} from "./EnumerableSet.sol";
  * - Entries are added, removed, and checked for existence in constant time
  * (O(1)).
  * - Entries are enumerated in O(n). No guarantees are made on the ordering.
+ * - Map can be cleared (all entries removed) in O(n).
  *
  * ```solidity
  * contract Example {
@@ -90,6 +91,20 @@ library EnumerableMap {
         return map._keys.remove(key);
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(Bytes32ToBytes32Map storage map) internal {
+        uint256 len = length(map);
+        for (uint256 i = 0; i < len; ++i) {
+            delete map._values[map._keys.at(i)];
+        }
+        map._keys.clear();
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -185,6 +200,16 @@ library EnumerableMap {
         return remove(map._inner, bytes32(key));
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(UintToUintMap storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -278,6 +303,16 @@ library EnumerableMap {
         return remove(map._inner, bytes32(key));
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(UintToAddressMap storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -371,6 +406,16 @@ library EnumerableMap {
         return remove(map._inner, bytes32(key));
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(UintToBytes32Map storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -464,6 +509,16 @@ library EnumerableMap {
         return remove(map._inner, bytes32(uint256(uint160(key))));
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(AddressToUintMap storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -557,6 +612,16 @@ library EnumerableMap {
         return remove(map._inner, bytes32(uint256(uint160(key))));
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(AddressToAddressMap storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -650,6 +715,16 @@ library EnumerableMap {
         return remove(map._inner, bytes32(uint256(uint160(key))));
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(AddressToBytes32Map storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -743,6 +818,16 @@ library EnumerableMap {
         return remove(map._inner, key);
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(Bytes32ToUintMap storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */
@@ -836,6 +921,16 @@ library EnumerableMap {
         return remove(map._inner, key);
     }
 
+    /**
+     * @dev Removes all the entries from a map. 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 map grows to the point where clearing it consumes too much gas to fit in a block.
+     */
+    function clear(Bytes32ToAddressMap storage map) internal {
+        clear(map._inner);
+    }
+
     /**
      * @dev Returns true if the key is in the map. O(1).
      */