From a61437eb3821756f0a67b7c1bdf3721f368973e3 Mon Sep 17 00:00:00 2001
From: Kristiyan Kostadinov <crisbeto@abv.bg>
Date: Sun, 28 Sep 2025 09:54:25 +0200
Subject: [PATCH] fix(material/select): rotate arrow while open

Rotates the select's arrow while it's open.

Fixes #29985.
Fixes #31869.
---
 src/material/select/select.scss | 8 ++++++++
 src/material/select/select.ts   | 1 +
 2 files changed, 9 insertions(+)

diff --git a/src/material/select/select.scss b/src/material/select/select.scss
index dcab8aa62662..960356863fc3 100644
--- a/src/material/select/select.scss
+++ b/src/material/select/select.scss
@@ -120,6 +120,14 @@ div.mat-mdc-select-panel {
     color: token-utils.slot(select-disabled-arrow-color, $fallbacks);
   }
 
+  .mat-select-open & {
+    transform: rotate(180deg);
+  }
+
+  .mat-form-field-animations-enabled & {
+    transition: transform variables.$swift-linear-duration variables.$swift-linear-timing-function;
+  }
+
   svg {
     fill: currentColor;
     position: absolute;
diff --git a/src/material/select/select.ts b/src/material/select/select.ts
index 1252711bb9d6..b05f7f8b6e3a 100644
--- a/src/material/select/select.ts
+++ b/src/material/select/select.ts
@@ -177,6 +177,7 @@ export class MatSelectChange<T = any> {
     '[class.mat-mdc-select-required]': 'required',
     '[class.mat-mdc-select-empty]': 'empty',
     '[class.mat-mdc-select-multiple]': 'multiple',
+    '[class.mat-select-open]': 'panelOpen',
     '(keydown)': '_handleKeydown($event)',
     '(focus)': '_onFocus()',
     '(blur)': '_onBlur()',