[Bug]: TypeError in ThemingDefaults::getColorPrimary() — preg_match() under PHP 8.4 on unset user primary_color

从 apps/theming/lib/ThemingDefaults.php 第 196 行附近开始，这里 getColorPrimary() 读取用户的 primary_color 并将其传给 preg_match()。检查与 ThemingDefaults 相关的测试，以及 getColorBackground() 是否以相同方式处理输入。确认未设置颜色时会回退到全局默认值且不会报错，然后运行相关的 theming 测试。

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When accessing /apps/files/ (or any page initializing user capabilities/theming) under PHP 8.4+, Nextcloud crashes with a fatal TypeError (HTTP 500) if the logged-in user does not have a custom primary_color configured.

In apps/theming/lib/ThemingDefaults.php line 196-197:

$userPrimaryColor = $this->userConfig->getValueString($user->getUID(), Application::APP_ID, 'primary_color');
if (preg_match('/^\#([0-9a-f]{3}|[0-9a-f]{6})$/i', $userPrimaryColor)) {
    return $userPrimaryColor;
}

Under PHP 8.4+, preg_match enforces strict types and no longer tolerates non-string types or certain uninitialized proxy representations from getValueString(), throwing:

TypeError: preg_match(): Argument #2 ($subject) must be of type string, string given at /var/www/html/apps/theming/lib/ThemingDefaults.php#197

Steps to reproduce

1. Run Nextcloud Server 34.x on PHP 8.4 (e.g. official nextcloud:34.0.5 Apache Docker image).
2. Log in as an admin or normal user who has never set a custom theming primary color.
3. Access /apps/files/.
4. The page fails with HTTP 500 Internal Server Error.

Expected behavior

Nextcloud should fall back gracefully to the global system primary color ($defaultColor) without throwing a fatal TypeError.

Nextcloud Server version

34

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.4

Web server

Apache (supported)

Database engine version

PostgreSQL

Is this bug present after an update or on a fresh install?

Updated from a MINOR version (ex. 32.0.1 to 32.0.2)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)

Nextcloud Logs

{
  "reqId": "n6FAHxGdzIB0H4OyzO55",
  "level": 3,
  "time": "2026-11-04T03:10:52+00:00",
  "remoteAddr": "x.x.x.x",
  "user": "admin",
  "app": "index",
  "method": "GET",
  "url": "/apps/files/",
  "message": "preg_match(): Argument #2 ($subject) must be of type string, string given",
  "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/27.2 Safari/605.1.15",
  "version": "34.0.5.1",
  "exception": {
    "Exception": "TypeError",
    "Message": "preg_match(): Argument #2 ($subject) must be of type string, string given",
    "Code": 0,
    "Trace": [
      {
        "function": "preg_match",
        "file": "/var/www/html/apps/theming/lib/ThemingDefaults.php",
        "line": 197,
        "args": ["/^\\#([0-9a-f]{3}|[0-9a-f]{6})$/i", ""]
      },
      {
        "file": "/var/www/html/apps/theming/lib/Capabilities.php",
        "line": 88,
        "function": "getColorPrimary",
        "class": "OCA\\Theming\\ThemingDefaults",
        "type": "->"
      },
      {
        "file": "/var/www/html/lib/private/CapabilitiesManager.php",
        "line": 60,
        "function": "getCapabilities",
        "class": "OCA\\Theming\\Capabilities",
        "type": "->"
      },
      {
        "file": "/var/www/html/lib/private/Template/JSConfigHelper.php",
        "line": 141,
        "function": "getCapabilities",
        "class": "OC\\CapabilitiesManager",
        "type": "->"
      },
      {
        "file": "/var/www/html/lib/private/TemplateLayout.php",
        "line": 251,
        "function": "getConfig",
        "class": "OC\\Template\\JSConfigHelper",
        "type": "->"
      },
      {
        "file": "/var/www/html/apps/files/lib/Controller/ViewController.php",
        "line": 202,
        "function": "dispatchTyped",
        "class": "OC\\EventDispatcher\\EventDispatcher",
        "type": "->"
      }
    ],
    "File": "/var/www/html/apps/theming/lib/ThemingDefaults.php",
    "Line": 197
  }
}

Suggested Fix

Add defensive type checks and explicit casting in apps/theming/lib/ThemingDefaults.php:

--- a/apps/theming/lib/ThemingDefaults.php
+++ b/apps/theming/lib/ThemingDefaults.php
@@ -194,7 +194,7 @@ class ThemingDefaults extends \OC_Defaults {
 		// user-defined primary color
 		if (!empty($user)) {
 			$userPrimaryColor = $this->userConfig->getValueString($user->getUID(), Application::APP_ID, 'primary_color');
-			if (preg_match('/^\#([0-9a-f]{3}|[0-9a-f]{6})$/i', $userPrimaryColor)) {
+			if (!empty($userPrimaryColor) && is_string($userPrimaryColor) && preg_match('/^\#([0-9a-f]{3}|[0-9a-f]{6})$/i', (string)$userPrimaryColor)) {
 				return $userPrimaryColor;
 			}
 		}

Similarly for getColorBackground() if applicable.