feat(ui5-mcb): introduces filter property (#2088)

Build-in filters are

 - StartsWithPerTerm
 - StartsWith
 - Contains
 - None

Users can now set filter to None and filter when input event is fired

FIXES: #799

packages/main/src/ComboBoxFilters.js

@@ -30,4 +30,11 @@ const Contains = (value, items) => {
 	});
 };
 
-export { StartsWithPerTerm, StartsWith, Contains };
+const None = (_, items) => items;
+
+export {
+	StartsWithPerTerm,
+	StartsWith,
+	Contains,
+	None,
+};

packages/main/src/MultiComboBox.js

@@ -24,7 +24,9 @@ import ResponsivePopover from "./ResponsivePopover.js";
 import List from "./List.js";
 import StandardListItem from "./StandardListItem.js";
 import ToggleButton from "./ToggleButton.js";
+import * as Filters from "./ComboBoxFilters.js";
 import Button from "./Button.js";
+
 import {
 	VALUE_STATE_SUCCESS,
 	VALUE_STATE_ERROR,
@@ -201,6 +203,19 @@ const metadata = {
 			type: Boolean,
 		},
 
+		/**
+		 * Defines the filter type of the <code>ui5-multi-combobox</code>.
+		 * Available options are: <code>StartsWithPerTerm</code>, <code>None</code>.
+		 *
+		 * @type {string}
+		 * @defaultvalue "StartsWithPerTerm"
+		 * @public
+		 */
+		filter: {
+			type: String,
+			defaultValue: "StartsWithPerTerm",
+		},
+
 		/**
 		 * Indicates whether the dropdown is open. True if the dropdown is open, false otherwise.
 		 *
@@ -586,12 +601,8 @@ class MultiComboBox extends UI5Element {
 		}
 	}
 
-	_filterItems(value) {
-		return this.items.filter(item => {
-			return item.text
-				&& item.text.toLowerCase().startsWith(value.toLowerCase())
-				&& (this.filterSelected ? item.selected : true);
-		});
+	_filterItems(str) {
+		return (Filters[this.filter] || Filters.StartsWithPerTerm)(str, this.items);
 	}
 
 	_toggle() {