fix(list): selection list not marking options as selected correctly when setting value with duplicates (#13363)

Along the same lines as #13361. Fixes the selection list not marking all selected options correctly when an array with duplicate values is assigned programmatically.

src/lib/list/selection-list.spec.ts

@@ -789,7 +789,7 @@ describe('MatSelectionList with forms', () => {
 
       expect(fixture.componentInstance.selectedOptions).toEqual(['opt2', 'opt3']);
 
-      fixture.componentInstance.renderLastOption = false;
+      fixture.componentInstance.options.pop();
       fixture.detectChanges();
       tick();
 
@@ -829,6 +829,20 @@ describe('MatSelectionList with forms', () => {
       expect(fixture.componentInstance.modelChangeSpy).not.toHaveBeenCalled();
     });
 
+    it('should be able to programmatically set an array with duplicate values', fakeAsync(() => {
+      fixture.componentInstance.options = ['one', 'two', 'two', 'two', 'three'];
+      fixture.detectChanges();
+      tick();
+
+      listOptions = fixture.debugElement.queryAll(By.directive(MatListOption))
+          .map(optionDebugEl => optionDebugEl.componentInstance);
+
+      fixture.componentInstance.selectedOptions = ['one', 'two', 'two'];
+      fixture.detectChanges();
+      tick();
+
+      expect(listOptions.map(option => option.selected)).toEqual([true, true, true, false, false]);
+    }));
 
   });
 
@@ -1076,15 +1090,13 @@ class SelectionListWithTabindexBinding {
 @Component({
   template: `
     <mat-selection-list [(ngModel)]="selectedOptions" (ngModelChange)="modelChangeSpy()">
-      <mat-list-option value="opt1">Option 1</mat-list-option>
-      <mat-list-option value="opt2">Option 2</mat-list-option>
-      <mat-list-option value="opt3" *ngIf="renderLastOption">Option 3</mat-list-option>
+      <mat-list-option *ngFor="let option of options" [value]="option">{{option}}</mat-list-option>
     </mat-selection-list>`
 })
 class SelectionListWithModel {
   modelChangeSpy = jasmine.createSpy('model change spy');
   selectedOptions: string[] = [];
-  renderLastOption = true;
+  options = ['opt1', 'opt2', 'opt3'];
 }
 
 @Component({

src/lib/list/selection-list.ts

@@ -473,13 +473,21 @@ export class MatSelectionList extends _MatSelectionListMixinBase implements Focu
   private _setOptionsFromValues(values: string[]) {
     this.options.forEach(option => option._setSelected(false));
 
-    values
-      .map(value => {
-        return this.options.find(option =>
-            this.compareWith ? this.compareWith(option.value, value) : option.value === value);
-      })
-      .filter(Boolean)
-      .forEach(option => option!._setSelected(true));
+    values.forEach(value => {
+      const correspondingOption = this.options.find(option => {
+        // Skip options that are already in the model. This allows us to handle cases
+        // where the same primitive value is selected multiple times.
+        if (option.selected) {
+          return false;
+        }
+
+        return this.compareWith ? this.compareWith(option.value, value) : option.value === value;
+      });
+
+      if (correspondingOption) {
+        correspondingOption._setSelected(true);
+      }
+    });
   }
 
   /** Returns the values of the selected options. */