fix: fixed issue where new items in Set where not recorded after iter…

…ating. Fixes #586

__tests__/map-set.js

@@ -225,5 +225,15 @@ function runBaseTest(name, useProxies, autoFreeze, useListener) {
 				}
 			])
 		})
+
+		test("#586", () => {
+			const base = new Set([1, 2])
+			const set = produce(base, draftSet => {
+				debugger
+				expect(Array.from(draftSet)).toEqual([1, 2])
+				draftSet.add(3)
+			})
+			expect(Array.from(set).sort()).toEqual([1, 2, 3])
+		})
 	})
 }

src/plugins/mapset.ts

@@ -241,9 +241,7 @@ export function enableMapSet() {
 		p.add = function(value: any): any {
 			const state: SetState = this[DRAFT_STATE]
 			assertUnrevoked(state)
-			if (state.copy_) {
-				state.copy_.add(value)
-			} else if (!state.base_.has(value)) {
+			if (!this.has(value)) {
 				prepareSetCopy(state)
 				markChanged(state.scope_.immer_, state)
 				state.copy_!.add(value)