Extend protection to multipolygon outer ways

js/id/actions/delete_way.js

@@ -33,12 +33,15 @@ iD.actions.DeleteWay = function(wayId) {
 
     action.disabled = function(graph) {
         var way = graph.entity(wayId);
-        var reltypes = ['route','boundary'];
+        var reltypes = ['route','boundary','multipolygon'];
+        var required_roles = { 'multipolygon': 'outer' };
         var disabled = false;
         graph.parentRelations(way)
             .forEach(function(parent) {
                 if (reltypes.indexOf(parent.tags.type)>-1) {
-                    disabled = 'part_of_relation';
+                    if (!required_roles[parent.tags.type] || parent.containsEntityInRole(way,required_roles[parent.tags.type])) {
+                        disabled = 'part_of_relation';
+                    }
                 }
             });
         return disabled;

js/id/core/relation.js

@@ -115,6 +115,16 @@ _.extend(iD.Relation.prototype, {
         }
     },
 
+    // Test whether the relation contains an entity in the given role.
+    containsEntityInRole: function(entity, role) {
+        for (var i = 0; i < this.members.length; i++) {
+            if (this.members[i].id === entity.id && this.members[i].type === entity.type && this.members[i].role === role) {
+                return true;
+            }
+        }
+        return false;
+    },
+
     addMember: function(member, index) {
         var members = this.members.slice();
         members.splice(index === undefined ? members.length : index, 0, member);