From 3e2ee4ba2f8d3a80c2cc006ccd185cfe6902c000 Mon Sep 17 00:00:00 2001
From: Kristiyan Kostadinov <crisbeto@abv.bg>
Date: Fri, 25 Jul 2025 09:11:40 +0200
Subject: [PATCH] fix(cdk/listbox): coerce tabindex value

Fixes that the CDK listbox option wasn't coercing its `tabindex` value.

Fixes #31595.
---
 goldens/cdk/listbox/index.api.md | 2 ++
 src/cdk/listbox/listbox.ts       | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/goldens/cdk/listbox/index.api.md b/goldens/cdk/listbox/index.api.md
index e4e97db2e089..16d788cf44e5 100644
--- a/goldens/cdk/listbox/index.api.md
+++ b/goldens/cdk/listbox/index.api.md
@@ -122,6 +122,8 @@ export class CdkOption<T = unknown> implements ListKeyManagerOption, Highlightab
     // (undocumented)
     static ngAcceptInputType_disabled: unknown;
     // (undocumented)
+    static ngAcceptInputType_enabledTabIndex: unknown;
+    // (undocumented)
     ngOnDestroy(): void;
     select(): void;
     setActiveStyles(): void;
diff --git a/src/cdk/listbox/listbox.ts b/src/cdk/listbox/listbox.ts
index b4405757ea89..8a327f9a15c4 100644
--- a/src/cdk/listbox/listbox.ts
+++ b/src/cdk/listbox/listbox.ts
@@ -39,6 +39,7 @@ import {
   inject,
   Input,
   NgZone,
+  numberAttribute,
   OnDestroy,
   Output,
   QueryList,
@@ -130,7 +131,10 @@ export class CdkOption<T = unknown> implements ListKeyManagerOption, Highlightab
   private _disabled = signal(false);
 
   /** The tabindex of the option when it is enabled. */
-  @Input('tabindex')
+  @Input({
+    alias: 'tabindex',
+    transform: (value: unknown) => (value == null ? undefined : numberAttribute(value)),
+  })
   get enabledTabIndex() {
     return this._enabledTabIndex() === undefined
       ? this.listbox.enabledTabIndex