Undefined property: Illuminate\Support\Number::$required

Using Laravel 11.36.1 with PHP 8.3, mews/purifier 3.4.2 and the latest version of ezyang/htmlpurifier.

When validating Number custom attributes, I get the following exception when i want to purify this string:

<p>Test</p>

This is the exception trace:

{
    "message": "Undefined property: Illuminate\\Support\\Number::$required",
    "exception": "ErrorException",
    "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrCollections.php",
    "line": 129,
    "trace": [
        {
            "file": "/var/www/html/vendor/laravel/framework/src/Illuminate/Foundation/Bootstrap/HandleExceptions.php",
            "line": 290,
            "function": "handleError",
            "class": "Illuminate\\Foundation\\Bootstrap\\HandleExceptions",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrCollections.php",
            "line": 129,
            "function": "Illuminate\\Foundation\\Bootstrap\\{closure}",
            "class": "Illuminate\\Foundation\\Bootstrap\\HandleExceptions",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLModuleManager.php",
            "line": 437,
            "function": "expandIdentifiers",
            "class": "HTMLPurifier_AttrCollections",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLModuleManager.php",
            "line": 361,
            "function": "getElement",
            "class": "HTMLPurifier_HTMLModuleManager",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLDefinition.php",
            "line": 253,
            "function": "getElements",
            "class": "HTMLPurifier_HTMLModuleManager",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLDefinition.php",
            "line": 195,
            "function": "processModules",
            "class": "HTMLPurifier_HTMLDefinition",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Definition.php",
            "line": 51,
            "function": "doSetup",
            "class": "HTMLPurifier_HTMLDefinition",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Config.php",
            "line": 497,
            "function": "setup",
            "class": "HTMLPurifier_Definition",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Config.php",
            "line": 415,
            "function": "getDefinition",
            "class": "HTMLPurifier_Config",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Generator.php",
            "line": 74,
            "function": "getHTMLDefinition",
            "class": "HTMLPurifier_Config",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/ezyang/htmlpurifier/library/HTMLPurifier.php",
            "line": 158,
            "function": "__construct",
            "class": "HTMLPurifier_Generator",
            "type": "->"
        },
        {
            "file": "/var/www/html/vendor/mews/purifier/src/Purifier.php",
            "line": 290,
            "function": "purify",
            "class": "HTMLPurifier",
            "type": "->"
        },
        // rest is omitted for clairty

Config:

return [
    'encoding' => 'UTF-8',
    'finalize' => true,
    'ignoreNonStrings' => false,
    'cachePath' => storage_path('app/purifier'),
    'cacheFileMode' => 0755,
    'settings' => [
        'default' => [
            'HTML.Doctype' => 'HTML 4.01 Transitional',
            'HTML.Allowed' => 'div,b,strong,i,em,u,a[href|title],ul,ol,li,p[style],br,span[style|data-mention|data-mention-user-id|data-mention-user-type],h1,h2,h3',
            'CSS.AllowedProperties' => 'font,font-size,font-weight,font-style,font-family,text-decoration,padding-left,color,background-color,text-align',
            'AutoFormat.AutoParagraph' => true,
            'AutoFormat.RemoveEmpty' => true,
        ],
        'custom_config_note' => [
            'HTML.Allowed' => 'div,b,strong,i,a[href|title],ul,ol,li,p,br,span[style|data-mention|data-mention-user-id|data-mention-user-type]',
            'AutoFormat.AutoParagraph' => true,
            'AutoFormat.RemoveEmpty' => true,
        ],
        'custom_config_svg_overlay' => [
            'HTML.Allowed' => 'svg,path[d|fill],circle[cx|cy|r|fill],rect[x|y|rx|ry|width|height]',
        ],
        'test' => [
            'Attr.EnableID' => 'true',
        ],
        "youtube" => [
            "HTML.SafeIframe" => 'true',
            "URI.SafeIframeRegexp" => "%^(http://|https://|//)(www.youtube.com/embed/|player.vimeo.com/video/)%",
        ],
        'custom_definition' => [
            'id' => 'html5-definitions',
            'rev' => 1,
            'debug' => false,
            'elements' => [
                // http://developers.whatwg.org/sections.html
                ['section', 'Block', 'Flow', 'Common'],
                ['nav', 'Block', 'Flow', 'Common'],
                ['article', 'Block', 'Flow', 'Common'],
                ['aside', 'Block', 'Flow', 'Common'],
                ['header', 'Block', 'Flow', 'Common'],
                ['footer', 'Block', 'Flow', 'Common'],

                // Content model actually excludes several tags, not modelled here
                ['address', 'Block', 'Flow', 'Common'],
                ['hgroup', 'Block', 'Required: h1 | h2 | h3 | h4 | h5 | h6', 'Common'],

                // http://developers.whatwg.org/grouping-content.html
                ['figure', 'Block', 'Optional: (figcaption, Flow) | (Flow, figcaption) | Flow', 'Common'],
                ['figcaption', 'Inline', 'Flow', 'Common'],

                // http://developers.whatwg.org/the-video-element.html#the-video-element
                ['video', 'Block', 'Optional: (source, Flow) | (Flow, source) | Flow', 'Common', [
                    'src' => 'URI',
                    'type' => 'Text',
                    'width' => 'Length',
                    'height' => 'Length',
                    'poster' => 'URI',
                    'preload' => 'Enum#auto,metadata,none',
                    'controls' => 'Bool',
                ]],
                ['source', 'Block', 'Flow', 'Common', [
                    'src' => 'URI',
                    'type' => 'Text',
                ]],

                // http://developers.whatwg.org/text-level-semantics.html
                ['s', 'Inline', 'Inline', 'Common'],
                ['var', 'Inline', 'Inline', 'Common'],
                ['sub', 'Inline', 'Inline', 'Common'],
                ['sup', 'Inline', 'Inline', 'Common'],
                ['mark', 'Inline', 'Inline', 'Common'],
                ['wbr', 'Inline', 'Empty', 'Core'],

                // http://developers.whatwg.org/edits.html
                ['ins', 'Block', 'Flow', 'Common', ['cite' => 'URI', 'datetime' => 'CDATA']],
                ['del', 'Block', 'Flow', 'Common', ['cite' => 'URI', 'datetime' => 'CDATA']],
            ],
            'attributes' => [
                ['iframe', 'allowfullscreen', 'Bool'],
                ['table', 'height', 'Text'],
                ['td', 'border', 'Text'],
                ['th', 'border', 'Text'],
                ['tr', 'width', 'Text'],
                ['tr', 'height', 'Text'],
                ['tr', 'border', 'Text'],
            ],
        ],
        'custom_attributes' => [
            ['a', 'target', 'Enum#_blank,_self,_target,_top'],

            // SVG <path> element attributes
            ['path', 'd', 'Text'],
            ['path', 'fill', 'Color'],

            // SVG <circle> element attributes
            ['circle', 'cx', 'Number'],
            ['circle', 'cy', 'Number'],
            ['circle', 'r', 'Number'],
            ['circle', 'fill', 'Color'],

            // SVG <rect> element attributes
            ['rect', 'rx', 'Number'],
            ['rect', 'ry', 'Number'],
            ['rect', 'x', 'Number'],
            ['rect', 'y', 'Number'],
            ['rect', 'width', 'Number'],
            ['rect', 'height', 'Number'],
            ['rect', 'pathLength', 'Number'],
            ['rect', 'fill', 'Color'],

            // CKEditor Mentions
            ['span', 'data-mention', 'Text'],
            ['span', 'data-mention-user-id', 'Text'],
            ['span', 'data-mention-user-type', 'Text'],
        ],
        'custom_elements' => [
            ['u', 'Inline', 'Inline', 'Common'],

            // SVG <path> element
            ['path', 'Inline', 'Empty', 'Common'],

            // SVG <circle> element
            ['circle', 'Inline', 'Empty', 'Common'],

            // SVG <rect> element
            ['rect', 'Inline', 'Empty', 'Common'],
        ],
    ],
];

Reproduce the issue with the shown custom_attributes Number configuration and the

Test

input. Start at vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrCollections.php line 129, then follow the HTMLPurifier_HTMLModuleManager.php calls; done means purification completes without the Undefined property exception.