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vendor/illuminate/database/Eloquent/Concerns/PreventsCircularRecursion.php

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+<?php
+
+namespace Illuminate\Database\Eloquent\Concerns;
+
+use Illuminate\Support\Arr;
+use Illuminate\Support\Onceable;
+use WeakMap;
+
+trait PreventsCircularRecursion
+{
+    /**
+     * The cache of objects processed to prevent infinite recursion.
+     *
+     * @var WeakMap<static, array<string, mixed>>
+     */
+    protected static $recursionCache;
+
+    /**
+     * Prevent a method from being called multiple times on the same object within the same call stack.
+     *
+     * @param  callable  $callback
+     * @param  mixed  $default
+     * @return mixed
+     */
+    protected function withoutRecursion($callback, $default = null)
+    {
+        $trace = debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT, 2);
+
+        $onceable = Onceable::tryFromTrace($trace, $callback);
+
+        if (is_null($onceable)) {
+            return call_user_func($callback);
+        }
+
+        $stack = static::getRecursiveCallStack($this);
+
+        if (array_key_exists($onceable->hash, $stack)) {
+            return is_callable($stack[$onceable->hash])
+                ? static::setRecursiveCallValue($this, $onceable->hash, call_user_func($stack[$onceable->hash]))
+                : $stack[$onceable->hash];
+        }
+
+        try {
+            static::setRecursiveCallValue($this, $onceable->hash, $default);
+
+            return call_user_func($onceable->callable);
+        } finally {
+            static::clearRecursiveCallValue($this, $onceable->hash);
+        }
+    }
+
+    /**
+     * Remove an entry from the recursion cache for an object.
+     *
+     * @param  object  $object
+     * @param  string  $hash
+     */
+    protected static function clearRecursiveCallValue($object, string $hash)
+    {
+        if ($stack = Arr::except(static::getRecursiveCallStack($object), $hash)) {
+            static::getRecursionCache()->offsetSet($object, $stack);
+        } elseif (static::getRecursionCache()->offsetExists($object)) {
+            static::getRecursionCache()->offsetUnset($object);
+        }
+    }
+
+    /**
+     * Get the stack of methods being called recursively for the current object.
+     *
+     * @param  object  $object
+     * @return array
+     */
+    protected static function getRecursiveCallStack($object): array
+    {
+        return static::getRecursionCache()->offsetExists($object)
+            ? static::getRecursionCache()->offsetGet($object)
+            : [];
+    }
+
+    /**
+     * Get the current recursion cache being used by the model.
+     *
+     * @return WeakMap
+     */
+    protected static function getRecursionCache()
+    {
+        return static::$recursionCache ??= new WeakMap();
+    }
+
+    /**
+     * Set a value in the recursion cache for the given object and method.
+     *
+     * @param  object  $object
+     * @param  string  $hash
+     * @param  mixed  $value
+     * @return mixed
+     */
+    protected static function setRecursiveCallValue($object, string $hash, $value)
+    {
+        static::getRecursionCache()->offsetSet(
+            $object,
+            tap(static::getRecursiveCallStack($object), fn (&$stack) => $stack[$hash] = $value),
+        );
+
+        return static::getRecursiveCallStack($object)[$hash];
+    }
+}