Add support for transformation max depths

config/data.php

@@ -120,6 +120,21 @@
      */
     'ignore_invalid_partials' => false,
 
+    /**
+     * When transforming a nested chain of data objects, the package can end up in an infinite
+     * loop when including a recursive relationship. The max transformation depth can be
+     * set as a safety measure to prevent this from happening. When set to null, the
+     * package will not enforce a maximum depth.
+     */
+    'max_transformation_depth' => null,
+
+    /**
+     * When the maximum transformation depth is reached, the package will throw an exception.
+     * You can disable this behaviour by setting this option to true which will return an
+     * empty array.
+     */
+    'fail_when_max_transformation_depth_reached' => true,
+
     /**
     * When using the `make:data` command, the package will use these settings to generate
     * the data classes. You can override these settings by passing options to the command.

docs/as-a-resource/transformers.md

@@ -154,3 +154,36 @@ ArtistData::from($artist)->transform(
 );
 ```
 
+## Transformation depth
+
+When transforming a complicated structure of nested data objects it is possible that an infinite loop is created of data objects including each other.
+To prevent this, a transformation depth can be set, when that depth is reached when transforming, either an exception will be thrown or an empty
+array is returned, stopping the transformation.
+
+This transformation depth can be set globally in the `data.php` config file:
+
+```php
+'max_transformation_depth' => 20,
+```
+
+It is also possible if a `MaxTransformationDepthReached` exception should be thrown or an empty array should be returned:
+
+```php
+'fail_when_max_transformation_depth_reached' => true,
+```
+
+It is also possible to set the transformation depth on a specific transformation by using a `TransformationContextFactory`:
+
+```php
+ArtistData::from($artist)->transform(
+    TransformationContextFactory::create()->maxDepth(20)
+);
+```
+
+By default, an exception will be thrown when the maximum transformation depth is reached. This can be changed to return an empty array as such:
+
+```php
+ArtistData::from($artist)->transform(
+    TransformationContextFactory::create()->maxDepth(20, fail: false)
+);
+```

src/Concerns/TransformableData.php

@@ -21,7 +21,10 @@ public function transform(
         $transformationContext = match (true) {
             $transformationContext instanceof TransformationContext => $transformationContext,
             $transformationContext instanceof TransformationContextFactory => $transformationContext->get($this),
-            $transformationContext === null => new TransformationContext()
+            $transformationContext === null => new TransformationContext(
+                maxDepth: config('data.max_transformation_depth'),
+                failWhenMaxDepthReached: config('data.fail_when_max_transformation_depth_reached')
+            )
         };
 
         $resolver = match (true) {

src/Exceptions/MaxTransformationDepthReached.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Spatie\LaravelData\Exceptions;
+
+use Exception;
+
+class MaxTransformationDepthReached extends Exception
+{
+    public static function create(int $depth): self
+    {
+        return new self("Max transformation depth of {$depth} reached.");
+    }
+}

src/Resolvers/Concerns/ChecksTransformationDepths.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Spatie\LaravelData\Resolvers\Concerns;
+
+use Spatie\LaravelData\Exceptions\MaxTransformationDepthReached;
+use Spatie\LaravelData\Support\Transformation\TransformationContext;
+
+trait ChecksTransformationDepths
+{
+    public function hasReachedMaxTransformationDepth(TransformationContext $context): bool
+    {
+        return $context->maxDepth !== null && $context->depth >= $context->maxDepth;
+    }
+
+    public function handleMaxDepthReached(TransformationContext $context): array
+    {
+        if ($context->failWhenMaxDepthReached) {
+            throw MaxTransformationDepthReached::create($context->maxDepth);
+        }
+
+        return [];
+    }
+}

src/Resolvers/TransformedDataCollectableResolver.php

@@ -14,6 +14,7 @@
 use Spatie\LaravelData\CursorPaginatedDataCollection;
 use Spatie\LaravelData\DataCollection;
 use Spatie\LaravelData\PaginatedDataCollection;
+use Spatie\LaravelData\Resolvers\Concerns\ChecksTransformationDepths;
 use Spatie\LaravelData\Support\DataConfig;
 use Spatie\LaravelData\Support\Transformation\TransformationContext;
 use Spatie\LaravelData\Support\Wrapping\Wrap;
@@ -22,6 +23,8 @@
 
 class TransformedDataCollectableResolver
 {
+    use ChecksTransformationDepths;
+
     public function __construct(
         protected DataConfig $dataConfig
     ) {
@@ -31,6 +34,10 @@ public function execute(
         iterable $items,
         TransformationContext $context,
     ): array {
+        if ($this->hasReachedMaxTransformationDepth($context)) {
+            return $this->handleMaxDepthReached($context);
+        }
+
         $wrap = $items instanceof WrappableData
             ? $items->getWrap()
             : new Wrap(WrapType::UseGlobal);

src/Resolvers/TransformedDataResolver.php

@@ -9,6 +9,7 @@
 use Spatie\LaravelData\Contracts\WrappableData;
 use Spatie\LaravelData\Lazy;
 use Spatie\LaravelData\Optional;
+use Spatie\LaravelData\Resolvers\Concerns\ChecksTransformationDepths;
 use Spatie\LaravelData\Support\DataClass;
 use Spatie\LaravelData\Support\DataConfig;
 use Spatie\LaravelData\Support\DataContainer;
@@ -20,6 +21,8 @@
 
 class TransformedDataResolver
 {
+    use ChecksTransformationDepths;
+
     public function __construct(
         protected DataConfig $dataConfig,
         protected VisibleDataFieldsResolver $visibleDataFieldsResolver,
@@ -30,6 +33,10 @@ public function execute(
         BaseData&TransformableData $data,
         TransformationContext $context,
     ): array {
+        if ($this->hasReachedMaxTransformationDepth($context)) {
+            return $this->handleMaxDepthReached($context);
+        }
+
         $dataClass = $this->dataConfig->getDataClass($data::class);
 
         $transformed = $this->transform($data, $context, $dataClass);
@@ -140,7 +147,7 @@ protected function resolvePropertyValue(
     protected function transformDataOrDataCollection(
         mixed $value,
         TransformationContext $currentContext,
-        ?TransformationContext $fieldContext
+        TransformationContext $fieldContext
     ): mixed {
         $wrapExecutionType = $this->resolveWrapExecutionType($value, $currentContext);
 
@@ -215,7 +222,7 @@ protected function resolvePotentialPartialArray(
         array $value,
         ?TransformationContext $fieldContext,
     ): array {
-        if($fieldContext === null) {
+        if ($fieldContext === null) {
             return $value;
         }
 

src/Resolvers/VisibleDataFieldsResolver.php

@@ -43,6 +43,9 @@ public function execute(
                     $transformationContext->mapPropertyNames,
                     $transformationContext->wrapExecutionType,
                     $transformationContext->transformers,
+                    depth: $transformationContext->depth + 1,
+                    maxDepth: $transformationContext->maxDepth,
+                    failWhenMaxDepthReached: $transformationContext->failWhenMaxDepthReached,
                 );
             }
         }

src/Support/Transformation/TransformationContext.php

@@ -24,6 +24,9 @@ public function __construct(
         public ?PartialsCollection $excludePartials = null,
         public ?PartialsCollection $onlyPartials = null,
         public ?PartialsCollection $exceptPartials = null,
+        public int $depth = 0,
+        public ?int $maxDepth = null,
+        public bool $failWhenMaxDepthReached = true,
     ) {
     }
 

src/Support/Transformation/TransformationContextFactory.php

@@ -27,6 +27,8 @@ protected function __construct(
         public ?PartialsCollection $excludePartials = null,
         public ?PartialsCollection $onlyPartials = null,
         public ?PartialsCollection $exceptPartials = null,
+        public ?int $maxDepth = null,
+        public bool $failWhenMaxDepthReached = true,
     ) {
     }
 
@@ -90,6 +92,9 @@ public function get(
             $excludePartials,
             $onlyPartials,
             $exceptPartials,
+            depth: 0,
+            maxDepth: $this->maxDepth,
+            failWhenMaxDepthReached: $this->failWhenMaxDepthReached,
         );
     }
 
@@ -155,6 +160,14 @@ public function withTransformer(string $transformable, Transformer|string $trans
         return $this;
     }
 
+    public function maxDepth(?int $maxDepth, bool $fail = true): static
+    {
+        $this->maxDepth = $maxDepth;
+        $this->failWhenMaxDepthReached = $fail;
+
+        return $this;
+    }
+
     public function mergeIncludePartials(PartialsCollection $partials): static
     {
         if ($this->includePartials === null) {

tests/PartialsTest.php

@@ -1476,20 +1476,20 @@ public function __construct()
         }
     };
 
-    //    expect($dataClass->include('collection.simple')->toArray())->toMatchArray([
-    //        'collection' => [
-    //            [
-    //                'simple' => [
-    //                    'string' => 'Rick Astley',
-    //                ],
-    //            ],
-    //            [
-    //                'simple' => [
-    //                    'string' => 'Jon Bon Jovi',
-    //                ],
-    //            ],
-    //        ],
-    //    ]);
+    expect($dataClass->include('collection.simple')->toArray())->toMatchArray([
+        'collection' => [
+            [
+                'simple' => [
+                    'string' => 'Rick Astley',
+                ],
+            ],
+            [
+                'simple' => [
+                    'string' => 'Jon Bon Jovi',
+                ],
+            ],
+        ],
+    ]);
 
     $nested = $dataClass->include('collection.simple')->all()['collection'];
 
@@ -1596,6 +1596,5 @@ public function __construct()
             ],
         ],
     ]);
-
     // Not really a test with expectation, we just want to check we don't end up in an infinite loop
 });

tests/Support/Transformation/TransformationContextFactoryTest.php

@@ -16,6 +16,9 @@
     expect($context->mapPropertyNames)->toBeTrue();
     expect($context->wrapExecutionType)->toBe(WrapExecutionType::Disabled);
     expect($context->transformers)->toBeNull();
+    expect($context->depth)->toBe(0);
+    expect($context->maxDepth)->toBeNull();
+    expect($context->failWhenMaxDepthReached)->toBeTrue();
 });
 
 it('can disable value transformation', function () {
@@ -82,3 +85,23 @@
     expect($context->transformers)->not()->toBe(null);
     expect($context->transformers->findTransformerForValue('Hello World'))->toBeInstanceOf(StringToUpperTransformer::class);
 });
+
+it('can set a max transformation depth', function () {
+    $context = TransformationContextFactory::create()
+        ->maxDepth(4)
+        ->get(SimpleData::from('Hello World'));
+
+    expect($context->maxDepth)->toBe(4);
+    expect($context->depth)->toBe(0);
+    expect($context->failWhenMaxDepthReached)->toBeTrue();
+});
+
+it('can set a max transformation depth without failing', function () {
+    $context = TransformationContextFactory::create()
+        ->maxDepth(4, fail: false)
+        ->get(SimpleData::from('Hello World'));
+
+    expect($context->maxDepth)->toBe(4);
+    expect($context->depth)->toBe(0);
+    expect($context->failWhenMaxDepthReached)->toBeFalse();
+});