Fix behavior of Zotero.Utilities.Internal.delayGenerator and add tests

Also convert to an ES6 generator

test/tests/utilities_internalTest.js

@@ -10,4 +10,58 @@ describe("Zotero.Utilities.Internal", function () {
 			);
 		})
 	})
+	
+	
+	describe("#delayGenerator", function () {
+		var spy;
+		
+		before(function () {
+			spy = sinon.spy(Zotero.Promise, "delay");
+		});
+		
+		afterEach(function () {
+			spy.reset();
+		});
+		
+		after(function () {
+			spy.restore();
+		});
+		
+		it("should delay for given amounts of time without limit", function* () {
+			var intervals = [1, 2];
+			var gen = Zotero.Utilities.Internal.delayGenerator(intervals);
+			
+			// When intervals are exhausted, keep using last interval
+			var testIntervals = intervals.slice();
+			testIntervals.push(intervals[intervals.length - 1]);
+			
+			for (let i of testIntervals) {
+				let val = yield gen.next().value;
+				assert.isTrue(val);
+				assert.isTrue(spy.calledWith(i));
+				spy.reset();
+			}
+		});
+		
+		it("should return false when maxTime is reached", function* () {
+			var intervals = [5, 10];
+			var gen = Zotero.Utilities.Internal.delayGenerator(intervals, 30);
+			
+			// When intervals are exhausted, keep using last interval
+			var testIntervals = intervals.slice();
+			testIntervals.push(intervals[intervals.length - 1]);
+			
+			for (let i of testIntervals) {
+				let val = yield gen.next().value;
+				assert.isTrue(val);
+				assert.isTrue(spy.calledWith(i));
+				spy.reset();
+			}
+			
+			// Another interval would put us over maxTime, so return false immediately
+			let val = yield gen.next().value;
+			assert.isFalse(val);
+			assert.isFalse(spy.called);
+		});
+	})
 })