test(json-crdt-extensions): 💍 add test for collapsed slice insertion

Author: streamich

src/json-crdt-extensions/peritext/overlay/Overlay.ts

@@ -375,7 +375,6 @@ export class Overlay<T = string> implements Printable, Stateful {
   }
 
   private insSlice(slice: Slice<T>): [start: OverlayPoint<T>, end: OverlayPoint<T>] {
-    // TODO: Test cases where the inserted slice is collapsed to one point.
     const x0 = slice.start;
     const x1 = slice.end;
     const [start, isStartNew] = this.upsertPoint(x0);
@@ -395,10 +394,7 @@ export class Overlay<T = string> implements Printable, Stateful {
       let curr: OverlayPoint<T> | undefined = start;
       do curr.addLayer(slice);
       while ((curr = next(curr)) && curr !== end);
-    } else {
-      // TODO: review if this is needed:
-      start.addMarker(slice);
-    }
+    } else start.addMarker(slice);
     return [start, end];
   }
 

src/json-crdt-extensions/peritext/overlay/__tests__/Overlay.spec.ts

@@ -161,6 +161,18 @@ describe('slices', () => {
       expect(points.length).toBe(4);
     });
 
+    test('can insert a slice, which is collapsed to a point', () => {
+      const {peritext} = setup();
+      peritext.editor.cursor.setAt(3);
+      const [slice] = peritext.editor.saved.insStack('em', {emphasis: true});
+      peritext.overlay.refresh();
+      const [point] = [...peritext.overlay.points()];
+      expect(point.layers.length).toBe(0);
+      expect(point.markers.length).toBe(2);
+      expect(point.markers.find((m) => m === peritext.editor.cursor)).toBe(peritext.editor.cursor);
+      expect(point.markers.find((m) => m === slice)).toBe(slice);
+    });
+
     test('intersecting slice chunks point to two slices', () => {
       const {peritext} = setup();
       peritext.editor.cursor.setAt(2, 2);