From c1a497f58c1710e354c4a531d8bda59d7d0ab962 Mon Sep 17 00:00:00 2001
From: ylorber <yann.lorber@amadeus.com>
Date: Wed, 6 May 2026 09:58:50 +0200
Subject: [PATCH] fix(material/select): stop event propagation on keyboard
 close in inline popover mode
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When mat-select uses inline popover positioning (the default), the CDK
overlay host is inserted inside the mat-select host element. This caused
keydown events (ENTER, SPACE, ALT+Arrow) handled by the open panel to
bubble up to the host element's listener, which then ran _handleClosedKeydown
and immediately re-opened the panel.

Fixed by calling event.stopPropagation() in _handleOpenKeydown for the
ENTER/SPACE selection and ALT+Arrow close branches. Also added a focus()
call before close() in the ALT+Arrow branch so focus is explicitly
restored to the trigger before the overlay detaches, consistent with
the Tab and ENTER paths.

This bug was particularly noticeable with screen readers since the panel
would re-open immediately after selection, causing aria-expanded to
toggle true→false→true in a single frame and confusing the a11y tree.
---
 src/material/select/select.ts | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/material/select/select.ts b/src/material/select/select.ts
index 94efdfec1f28..8e153c842b64 100644
--- a/src/material/select/select.ts
+++ b/src/material/select/select.ts
@@ -942,6 +942,11 @@ export class MatSelect
     if (isArrowKey && event.altKey) {
       // Close the select on ALT + arrow key to match the native <select>
       event.preventDefault();
+      // Stop propagation so the event doesn't bubble to the host element and trigger
+      // _handleClosedKeydown, which would re-open the panel immediately.
+      event.stopPropagation();
+      // Restore focus to the trigger before closing so focus isn't lost when the overlay detaches.
+      this.focus();
       this.close();
       // Don't do anything in this case if the user is typing,
       // because the typing sequence can include the space key.
@@ -952,6 +957,9 @@ export class MatSelect
       !hasModifierKey(event)
     ) {
       event.preventDefault();
+      // Stop propagation so the event doesn't bubble to the host element and trigger
+      // _handleClosedKeydown, which would re-open the panel immediately.
+      event.stopPropagation();
       manager.activeItem._selectViaInteraction();
     } else if (!isTyping && this._multiple && keyCode === A && event.ctrlKey) {
       event.preventDefault();