fix(core): ObservableArray splice with start only (#9159)

packages/core/__tests__/observable/observable-array.ts

@@ -0,0 +1,47 @@
+import { ObservableArray } from '@nativescript/core/data/observable-array';
+import { assert } from 'chai';
+
+describe('observable-array', () => {
+	describe('splice', () => {
+		it('removes an item', () => {
+			const _array = new ObservableArray();
+
+			_array.push(1);
+			_array.push(2);
+
+			_array.splice(0, 1);
+
+			assert.equal(2, _array.getItem(0));
+		});
+
+		it('replaces an item', () => {
+			const _array = new ObservableArray();
+
+			_array.push(1);
+			_array.push(2);
+
+			_array.splice(0, 1, 3);
+
+			assert.equal(3, _array.getItem(0));
+		});
+
+		it('empties on start zero and no delete count', () => {
+			const _array = new ObservableArray();
+
+			_array.push(1);
+
+			_array.splice(0);
+			assert.equal(0, _array.length);
+		});
+
+		it('empties on length set to zero', () => {
+			const _array = new ObservableArray();
+
+			_array.push(1);
+			_array.push(2);
+
+			_array.length = 0;
+			assert.equal(0, _array.length);
+		});
+	});
+});

packages/core/data/observable-array/index.ts

@@ -246,7 +246,7 @@ export class ObservableArray<T> extends Observable {
 	 */
 	splice(start: number, deleteCount?: number, ...items: any): T[] {
 		const length = this._array.length;
-		const result = this._array.splice(start, deleteCount, ...items);
+		const result = arguments.length === 1 ? this._array.splice(start) : this._array.splice(start, deleteCount, ...items);
 
 		this.notify(<ChangedData<T>>{
 			eventName: CHANGE,