fix(searchWhileComposing): control whether items should be filtered while composing

fixes ng-select#1296, default `true`

Author: varnastadeus

README.md

@@ -152,6 +152,7 @@ map: {
 | [searchable] | `boolean` | `true` | no | Allow to search for value. Default `true`|
 | [readonly] | `boolean` | `false` | no | Set ng-select as readonly. Mostly used with reactive forms. |
 | [searchFn] | `(term: string, item: any) => boolean` | `null` | no | Allow to filter by custom search function |
+| [searchWhileComposing] | `boolean` | `true` | no | Whether items should be filtered while composition started |
 | [trackByFn] | `(item: any) => any` | `null` | no | Provide custom trackBy function |
 | [clearSearchOnAdd] | `boolean` | `true` | no | Clears search input when item is selected. Default `true`. Default `false` when **closeOnSelect** is `false` |
 | [selectOnTab] | `boolean` | `false` | no | Select marked dropdown item using tab. Default `false`|

src/ng-select/lib/ng-select.component.spec.ts

@@ -3600,6 +3600,7 @@ describe('NgSelectComponent', () => {
                 `<ng-select [items]="citiesNames"
                     [addTag]="true"
                     placeholder="select value"
+                    [searchWhileComposing]="false"
                     [(ngModel)]="selectedCity">
                 </ng-select>`);
             select = fixture.componentInstance.select;

src/ng-select/lib/ng-select.component.ts

@@ -107,6 +107,7 @@ export class NgSelectComponent implements OnDestroy, OnChanges, AfterViewInit, C
     @Input() inputAttrs: { [key: string]: string } = {};
     @Input() tabIndex: number;
     @Input() readonly = false;
+    @Input() searchWhileComposing = true;
     @Input() keyDownFn = (_: KeyboardEvent) => true;
 
     @Input() @HostBinding('class.ng-select-typeahead') typeahead: Subject<string>;
@@ -192,14 +193,13 @@ export class NgSelectComponent implements OnDestroy, OnChanges, AfterViewInit, C
     private _pressedKeys: string[] = [];
     private _compareWith: CompareWithFn;
     private _clearSearchOnAdd: boolean;
+    private _isComposing = false;
 
     private readonly _destroy$ = new Subject<void>();
     private readonly _keyPress$ = new Subject<string>();
     private _onChange = (_: any) => { };
     private _onTouched = () => { };
 
-    private _isComposing = false;
-
     clearItem = (item: any) => {
         const option = this.selectedItems.find(x => x.value === item);
         this.unselect(option);
@@ -535,12 +535,15 @@ export class NgSelectComponent implements OnDestroy, OnChanges, AfterViewInit, C
     }
 
     onCompositionEnd(term: string) {
+        if (this.searchWhileComposing) {
+            return;
+        }
         this._isComposing = false;
         this.filter(term);
     }
 
     filter(term: string) {
-        if (this._isComposing) {
+        if (this._isComposing && !this.searchWhileComposing) {
             return;
         }
         this._changeSearch(term);