Revert when setting zero address zone or setting to already allowed value

Author: lfportal

contracts/trading/seaport16/ImmutableSeaport.sol

@@ -26,6 +26,7 @@ contract ImmutableSeaport is Consideration, Ownable, ImmutableSeaportEvents {
     mapping(address => bool) public allowedZones;
 
     error OrderNotRestricted(uint8 orderType);
+    error AllowedZoneAlreadySet(address zone);
     error InvalidZone(address zone);
 
     /**
@@ -48,6 +49,12 @@ contract ImmutableSeaport is Consideration, Ownable, ImmutableSeaportEvents {
      * @dev Set the validity of a zone for use during fulfillment.
      */
     function setAllowedZone(address zone, bool allowed) external onlyOwner {
+        require(zone != address(0), "ImmutableSeaport: zone is the zero address");
+
+        if (allowedZones[zone] == allowed) {
+            revert AllowedZoneAlreadySet(zone);
+        }
+
         allowedZones[zone] = allowed;
         emit AllowedZoneSet(zone, allowed);
     }

test/trading/seaport16/ImmutableSeaportConfig.t.sol

@@ -2,9 +2,9 @@
 pragma solidity ^0.8.13;
 
 import {ImmutableSeaportBaseTest} from "./ImmutableSeaportBase.t.sol";
+import {ImmutableSeaport} from "../../../contracts/trading/seaport16/ImmutableSeaport.sol";
 
 contract ImmutableSeaportConfigTest is ImmutableSeaportBaseTest {
-
     function testEmitsAllowedZoneSetEvent() public {
         address zone = makeAddr("zone");
         bool allowed = true;
@@ -14,4 +14,21 @@ contract ImmutableSeaportConfigTest is ImmutableSeaportBaseTest {
         emit AllowedZoneSet(zone, allowed);
         immutableSeaport.setAllowedZone(zone, allowed);
     }
+
+    function testRejectZeroAddressZone() public {
+        vm.prank(owner);
+        vm.expectRevert("ImmutableSeaport: zone is the zero address");
+        immutableSeaport.setAllowedZone(address(0), true);
+    }
+
+    function testRejectAllowedZoneAlreadySet() public {
+        address zone = makeAddr("zone");
+
+        vm.prank(owner);
+        immutableSeaport.setAllowedZone(zone, true);
+
+        vm.prank(owner);
+        vm.expectRevert(abi.encodeWithSelector(ImmutableSeaport.AllowedZoneAlreadySet.selector, zone));
+        immutableSeaport.setAllowedZone(zone, true);
+    }
 }