Include multipolygon members in complete()

(closes #3613)

modules/core/difference.js

@@ -1,7 +1,7 @@
 import deepEqual from 'fast-deep-equal';
 
 import { geoVecEqual } from '../geo';
-import { utilArrayDifference } from '../util';
+import { utilArrayDifference, utilArrayUnion } from '../util';
 
 
 /*
@@ -173,6 +173,8 @@ export function coreDifference(base, head) {
     };
 
 
+    // returns complete set of entities that require a redraw
+    //  (optionally within given `extent`)
     _diff.complete = function complete(extent) {
         var result = {};
         var id, change;
@@ -183,6 +185,7 @@ export function coreDifference(base, head) {
             var h = change.head;
             var b = change.base;
             var entity = h || b;
+            var i;
 
             if (extent &&
                 (!h || !h.intersects(extent, head)) &&
@@ -194,7 +197,7 @@ export function coreDifference(base, head) {
             if (entity.type === 'way') {
                 var nh = h ? h.nodes : [];
                 var nb = b ? b.nodes : [];
-                var diff, i;
+                var diff;
 
                 diff = utilArrayDifference(nh, nb);
                 for (i = 0; i < diff.length; i++) {
@@ -207,6 +210,15 @@ export function coreDifference(base, head) {
                 }
             }
 
+            if (entity.type === 'relation' && entity.isMultipolygon()) {
+                var mh = h ? h.members.map(function(m) { return m.id; }) : [];
+                var mb = b ? b.members.map(function(m) { return m.id; }) : [];
+                var ids = utilArrayUnion(mh, mb);
+                for (i = 0; i < ids.length; i++) {
+                    result[ids[i]] = head.hasEntity(ids[i]);
+                }
+            }
+
             addParents(head.parentWays(entity), result);
             addParents(head.parentRelations(entity), result);
         }

test/spec/core/difference.js

@@ -382,6 +382,22 @@ describe('iD.coreDifference', function () {
             expect(diff.complete().n2).to.equal(n2);
         });
 
+        it('includes multipolygon members', function () {
+            var w1 = iD.osmWay({id: 'w1'});
+            var w2 = iD.osmWay({id: 'w2'});
+            var r1 = iD.osmRelation({
+                id: 'r',
+                tags: { type: 'multipolygon' },
+                members: [{role: 'outer', id: 'w1', type: 'way'}, {role: '', id: 'w2', type: 'way'}]
+            });
+            var r2 = r1.updateMember({role: 'inner', id: 'w2', type: 'way'}, 1);
+            var base = iD.coreGraph([w1, w2, r1]);
+            var head = base.replace(r2);
+            var diff = iD.coreDifference(base, head);
+
+            expect(diff.complete().w2).to.equal(w2);
+        });
+
         it('includes parent ways of modified nodes', function () {
             var n1   = iD.osmNode({id: 'n'});
             var n2   = n1.move([1, 2]);