fix(select): do not emit change event when same value selected twice

PiperOrigin-RevId: 320435732
material-components · Jul 9, 2020 · e07a708 · e07a708
1 parent d850de5
commit e07a708
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Showing 2 changed files with 6 additions and 1 deletion.
diff --git a/packages/mdc-select/foundation.ts b/packages/mdc-select/foundation.ts
@@ -102,6 +102,7 @@ export class MDCSelectFoundation extends MDCFoundation<MDCSelectAdapter> {
   // By default, select is invalid if it is required but no value is selected.
   private useDefaultValidation = true;
   private customValidity = true;
+  private lastSelectedIndex = numbers.UNSET_INDEX;
 
   /* istanbul ignore next: optional argument is not a branch statement */
   /**
@@ -138,9 +139,10 @@ export class MDCSelectFoundation extends MDCFoundation<MDCSelectAdapter> {
       this.adapter.closeMenu();
     }
 
-    if (!skipNotify) {
+    if (!skipNotify && this.lastSelectedIndex !== index) {
       this.handleChange();
     }
+    this.lastSelectedIndex = index;
   }
 
   setValue(value: string) {

diff --git a/packages/mdc-select/test/foundation.test.ts b/packages/mdc-select/test/foundation.test.ts
@@ -774,6 +774,9 @@ describe('MDCSelectFoundation', () => {
     foundation.setSelectedIndex(1);
     expect(mockAdapter.setSelectedIndex).toHaveBeenCalledWith(1);
 
+    foundation.setSelectedIndex(0);
+    // We intentionally call this twice, expecting notifyChange to be called
+    // only once for these two calls.
     foundation.setSelectedIndex(0);
     expect(mockAdapter.setSelectedIndex).toHaveBeenCalledWith(0);