[11.x] Handle circular references in model serialization (#52461)

* [11.x] Added failing test for serializing circular relations

If a circular relationship is set up between two models using
 `setRelation()` (or similar methods) then calling
 `$model->relationsToArray()` will call `toArray()` on each related
 model, which will in turn call `relationsToArray()`. In an instance
 where one of the related models is an object that has already had
 `toArray()` called further up the stack, it will infinitely recurse
  down and result in a stack overflow.

The same issue exists with `getQueueableRelations()`, `push()`, and
 potentially other methods. This adds tests which will fail if one of
 the known potentially problematic methods gets into a recursive loop.

* [11.x] Added PreventsCircularRecursion

This adds a trait for Eloquent which can be used to prevent recursively
 serializing circular references.

* [11.x] Changed the name to `withoutRecursion()`, accept a callable default

* formatting

* [11.x] Delay calling a "default" callback until the last possible second

* [11.x] Added additional tests for "callable" defaults

---------

Co-authored-by: Taylor Otwell <taylor@laravel.com>

Author: samlev

src/Illuminate/Database/Eloquent/Concerns/PreventsCircularRecursion.php

@@ -0,0 +1,103 @@
+<?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);
+
+        $stack = static::getRecursiveCallStack($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];
+    }
+}

src/Illuminate/Database/Eloquent/Model.php

@@ -35,6 +35,7 @@ abstract class Model implements Arrayable, ArrayAccess, CanBeEscapedWhenCastToSt
         Concerns\HasUniqueIds,
         Concerns\HidesAttributes,
         Concerns\GuardsAttributes,
+        Concerns\PreventsCircularRecursion,
         ForwardsCalls;
     /** @use HasCollection<\Illuminate\Database\Eloquent\Collection<array-key, static>> */
     use HasCollection;
@@ -1083,25 +1084,27 @@ protected function decrementQuietly($column, $amount = 1, array $extra = [])
      */
     public function push()
     {
-        if (! $this->save()) {
-            return false;
-        }
-
-        // To sync all of the relationships to the database, we will simply spin through
-        // the relationships and save each model via this "push" method, which allows
-        // us to recurse into all of these nested relations for the model instance.
-        foreach ($this->relations as $models) {
-            $models = $models instanceof Collection
-                ? $models->all() : [$models];
+        return $this->withoutRecursion(function () {
+            if (! $this->save()) {
+                return false;
+            }
 
-            foreach (array_filter($models) as $model) {
-                if (! $model->push()) {
-                    return false;
+            // To sync all of the relationships to the database, we will simply spin through
+            // the relationships and save each model via this "push" method, which allows
+            // us to recurse into all of these nested relations for the model instance.
+            foreach ($this->relations as $models) {
+                $models = $models instanceof Collection
+                    ? $models->all() : [$models];
+
+                foreach (array_filter($models) as $model) {
+                    if (! $model->push()) {
+                        return false;
+                    }
                 }
             }
-        }
 
-        return true;
+            return true;
+        }, true);
     }
 
     /**
@@ -1657,7 +1660,10 @@ public function callNamedScope($scope, array $parameters = [])
      */
     public function toArray()
     {
-        return array_merge($this->attributesToArray(), $this->relationsToArray());
+        return $this->withoutRecursion(
+            fn () => array_merge($this->attributesToArray(), $this->relationsToArray()),
+            fn () => $this->attributesToArray(),
+        );
     }
 
     /**
@@ -2004,29 +2010,31 @@ public function getQueueableId()
      */
     public function getQueueableRelations()
     {
-        $relations = [];
+        return $this->withoutRecursion(function () {
+            $relations = [];
 
-        foreach ($this->getRelations() as $key => $relation) {
-            if (! method_exists($this, $key)) {
-                continue;
-            }
+            foreach ($this->getRelations() as $key => $relation) {
+                if (! method_exists($this, $key)) {
+                    continue;
+                }
 
-            $relations[] = $key;
+                $relations[] = $key;
 
-            if ($relation instanceof QueueableCollection) {
-                foreach ($relation->getQueueableRelations() as $collectionValue) {
-                    $relations[] = $key.'.'.$collectionValue;
+                if ($relation instanceof QueueableCollection) {
+                    foreach ($relation->getQueueableRelations() as $collectionValue) {
+                        $relations[] = $key.'.'.$collectionValue;
+                    }
                 }
-            }
 
-            if ($relation instanceof QueueableEntity) {
-                foreach ($relation->getQueueableRelations() as $entityValue) {
-                    $relations[] = $key.'.'.$entityValue;
+                if ($relation instanceof QueueableEntity) {
+                    foreach ($relation->getQueueableRelations() as $entityValue) {
+                        $relations[] = $key.'.'.$entityValue;
+                    }
                 }
             }
-        }
 
-        return array_unique($relations);
+            return array_unique($relations);
+        }, []);
     }
 
     /**