Don't-preserve-keys mode

src/Attribute/Collection.php

@@ -19,9 +19,11 @@
 class Collection
 {
     /**
-     * @param string|null $indexBy property of the elements to use as keys instead of their position, can be a property merged by inline
+     * @param bool        $preserveKeys whether to preserve keys of the collection
+     * @param string|null $indexBy      property of the elements to use as keys instead of their position, can be a property merged by inline
      */
     public function __construct(
+        public bool $preserveKeys = true,
         public ?string $indexBy = null,
     ) {
     }

src/Compiler/SpecializedNormalizerCompiler.php

@@ -337,6 +337,7 @@ protected function compileNormalizerClass(StreamWriter $fd, ResolvedClassInfo $c
                 $fd
                     ->printfln('\'inline_property\'   => %s,', \var_export($meta->inlineSubProperty, true))
                     ->printfln('\'index_by_property\' => %s,', \var_export($meta->indexBySubProperty, true))
+                    ->printfln('\'preserve_keys\'     => %s,', \var_export($meta->preserveKeys, true))
                     ->printfln('\'skip_property\'     => %s,', \var_export(null !== $inverseMeta && null !== $inverseMeta->type && $inverseMeta->type->isCollection() ? null : $meta->inverseSubProperty, true))
                     ->printfln('\'inbound_property\'  => %s,', \var_export($property, true))
                     ->outdent()
@@ -369,7 +370,6 @@ protected function compileNormalizerClass(StreamWriter $fd, ResolvedClassInfo $c
         /* ----- Breadth-first Normalization ----- */
 
         $fd
-            ->printfln('/** @param T $object */')
             ->printfln('private function normalizeBreadthFirst(T $object, ?string $format = null, array $context = []): void')
             ->printfln('{')
             ->indent()
@@ -492,6 +492,7 @@ protected function compileNormalizerClass(StreamWriter $fd, ResolvedClassInfo $c
                 $fd
                     ->printfln('\'inline_property\'   => %s,', \var_export($meta->inlineSubProperty, true))
                     ->printfln('\'index_by_property\' => %s,', \var_export($meta->indexBySubProperty, true))
+                    ->printfln('\'preserve_keys\'     => %s,', \var_export($meta->preserveKeys, true))
                     ->printfln('\'skip_property\'     => %s,', \var_export(null !== $inverseMeta && null !== $inverseMeta->type && $inverseMeta->type->isCollection() ? null : $meta->inverseSubProperty, true))
                     ->printfln('\'inbound_property\'  => %s,', \var_export($property, true))
                     ->printfln('\'continuation\'      => $inline ? ($context[\'continuation\'] ?? null) : null,', \var_export($property, true))

src/Metadata/AutoNormalizableMetadataProvider.php

@@ -212,6 +212,7 @@ public function getNormalizableProperties(string $className): array
                 }
             }
             if (null !== $collectionAttribute) {
+                $property->preserveKeys = $collectionAttribute->preserveKeys;
                 $property->indexBySubProperty = $collectionAttribute->indexBy;
             }
         }

src/Metadata/NormalizableProperty.php

@@ -22,6 +22,7 @@ class NormalizableProperty
 
     public bool $alwaysNormalize = false;
     public ?Type $type = null;
+    public bool $preserveKeys = true;
     public ?string $indexBySubProperty = null;
     public ?string $inlineSubProperty = null;
     public ?string $inverseSubProperty = null;

src/Normalizer/CollectionNormalizer.php

@@ -159,8 +159,14 @@ public function normalize($object, $format = null, array $context = []): array|\
         }
 
         $normalized = [];
-        foreach ($object as $key => $element) {
-            $normalized[$key] = $this->normalizer->normalize($element, $format, $context);
+        if ($context['preserve_keys'] ?? true) {
+            foreach ($object as $key => $element) {
+                $normalized[$key] = $this->normalizer->normalize($element, $format, $context);
+            }
+        } else {
+            foreach ($object as $element) {
+                $normalized[] = $this->normalizer->normalize($element, $format, $context);
+            }
         }
 
         if (isset($context['index_by_property'])) {
@@ -179,7 +185,7 @@ public function normalize($object, $format = null, array $context = []): array|\
         return $normalized;
     }
 
-    private function normalizeBreadthFirst($object, ?string $format, array $context): void
+    private function normalizeBreadthFirst(iterable $object, ?string $format, array $context): void
     {
         $helper = $context['breadth_first_helper'];
         $normalized = &$helper->getCurrentBindPoint();
@@ -227,12 +233,18 @@ private function normalizeBreadthFirst($object, ?string $format, array $context)
             if ($empty) {
                 $normalized = new \stdClass();
             }
-        } else {
+        } elseif ($context['preserve_keys'] ?? true) {
             foreach ($object as $key => $element) {
                 $helper->bind($normalized[$key], $this->normalizer, $element, $format, [
                     'continuation' => null,
                 ] + $context);
             }
+        } else {
+            foreach ($object as $element) {
+                $helper->bind($normalized[], $this->normalizer, $element, $format, [
+                    'continuation' => null,
+                ] + $context);
+            }
         }
 
         if (isset($context['continuation'])) {