prevent degenerate ways caused by deleting a corner of a triangle

Author: k-yle

modules/osm/way.js

@@ -242,7 +242,7 @@ Object.assign(osmWay.prototype, {
 
 
     isDegenerate: function() {
-        return (new Set(this.nodes).size < (this.isArea() ? 3 : 2));
+        return (new Set(this.nodes).size < (this.isClosed() ? 3 : 2));
     },
 
 

test/spec/osm/way.js

@@ -473,6 +473,10 @@ describe('iD.osmWay', function() {
             expect(iD.osmWay({nodes: ['a', 'b']}).isDegenerate()).to.equal(false);
         });
 
+        it('returns true for a linear way that doubles back on itself', function () {
+            expect(iD.osmWay({nodes: ['a', 'b', 'a']}).isDegenerate()).to.equal(true);
+        });
+
         it('returns true for an area with zero, one, or two unique nodes', function () {
             expect(iD.osmWay({tags: {area: 'yes'}, nodes: []}).isDegenerate()).to.equal(true);
             expect(iD.osmWay({tags: {area: 'yes'}, nodes: ['a', 'a']}).isDegenerate()).to.equal(true);