fix(ui5-multi-combobox): adjust open property handling (#7763)

packages/main/src/MultiComboBox.ts

@@ -353,19 +353,6 @@ class MultiComboBox extends UI5Element {
 	@property({ type: ComboBoxFilter, defaultValue: ComboBoxFilter.StartsWithPerTerm })
 	filter!: `${ComboBoxFilter}`;
 
-	/**
-	 * Indicates whether the dropdown is open. True if the dropdown is open, false otherwise.
-	 *
-	 * @type {boolean}
-	 * @name sap.ui.webc.main.MultiComboBox.prototype.open
-	 * @defaultvalue false
-	 * @readonly
-	 * @since 1.0.0-rc.5
-	 * @public
-	 */
-	@property({ type: Boolean })
-	open!: boolean;
-
 	/**
 	 * Defines the accessible ARIA name of the component.
 	 *
@@ -390,6 +377,16 @@ class MultiComboBox extends UI5Element {
 	@property()
 	accessibleNameRef!: string;
 
+	/**
+	 * Indicates whether the dropdown is open. True if the dropdown is open, false otherwise.
+	 *
+	 * @type {boolean}
+	 * @defaultvalue false
+	 * @private
+	 */
+	@property({ type: Boolean })
+	_open!: boolean;
+
 	@property({ type: Object, noAttribute: true, multiple: true })
 	_filteredItems!: Array<IMultiComboBoxItem>;
 
@@ -545,6 +542,19 @@ class MultiComboBox extends UI5Element {
 		this.selectedItems = this.items.filter((item, idx, allItems) => MultiComboBox._groupItemFilter(item, ++idx, allItems, selectedItems) || selectedItems.indexOf(item) !== -1);
 	}
 
+	/**
+	 * Indicates whether the dropdown is open. True if the dropdown is open, false otherwise.
+	 *
+	 * @type {boolean}
+	 * @name sap.ui.webc.main.MultiComboBox.prototype.open
+	 * @defaultvalue false
+	 * @readonly
+	 * @public
+	 */
+	get open() {
+		return this._open;
+	}
+
 	get _showAllItemsButtonPressed(): boolean {
 		return this.filterSelected;
 	}
@@ -1251,7 +1261,7 @@ class MultiComboBox extends UI5Element {
 	}
 
 	_toggle() {
-		this.open = !this.open;
+		this._open = !this._open;
 		this.fireEvent("open-change");
 	}