fix(navigation): fix swipe-to-go-back

fix swipe-to-go-back

src/navigation/nav-controller-base.ts

@@ -1048,7 +1048,7 @@ export class NavControllerBase extends Ion implements NavController {
   canSwipeBack(): boolean {
     return (this._sbEnabled &&
             !this._isPortal &&
-            this._child &&
+            !this._child &&
             !this.isTransitioning() &&
             this._app.isEnabled() &&
             this.canGoBack());

src/navigation/test/nav-controller.spec.ts

@@ -1100,7 +1100,53 @@ describe('NavController', () => {
         });
       nav.destroy();
     }, 10000);
+  });
+
+  describe('canSwipeBack', () => {
+    it('should not swipe back when its not enabled', () => {
+      nav._sbEnabled = false;
+
+      const view1 = mockView();
+      const view2 = mockView();
+      mockViews(nav, [view1, view2]);
+
+      const result = nav.canSwipeBack();
+      expect(result).toEqual(false);
+    });
+
+    it('should not swipe back if its the portal', () => {
+      nav._sbEnabled = true;
+      nav._isPortal = true;
 
+      const view1 = mockView();
+      const view2 = mockView();
+      mockViews(nav, [view1, view2]);
+
+      const result = nav.canSwipeBack();
+      expect(result).toEqual(false);
+    });
+
+    it('should not swipe back if it has a child nav', () => {
+      nav._sbEnabled = true;
+      nav._child = mockNavController();
+
+      const view1 = mockView();
+      const view2 = mockView();
+      mockViews(nav, [view1, view2]);
+
+      const result = nav.canSwipeBack();
+      expect(result).toEqual(false);
+    });
+
+    it('should swipe back when has a view to go back to', () => {
+      nav._sbEnabled = true;
+      const view1 = mockView();
+      const view2 = mockView();
+      mockViews(nav, [view1, view2]);
+
+      const result = nav.canSwipeBack();
+      expect(result).toEqual(true);
+    });
   });