Traverser: can return different nodes

src/Neon/Node/ArrayItemNode.php

@@ -86,6 +86,6 @@ public function toString(callable $serializer = null): string
 
 	public function getSubNodes(): array
 	{
-		return $this->key ? [$this->key, $this->value] : [$this->value];
+		return $this->key ? [&$this->key, &$this->value] : [&$this->value];
 	}
 }

src/Neon/Node/ArrayNode.php

@@ -53,6 +53,10 @@ public function toString(callable $serializer = null): string
 
 	public function getSubNodes(): array
 	{
-		return $this->items;
+		$res = [];
+		foreach ($this->items as &$item) {
+			$res[] = &$item;
+		}
+		return $res;
 	}
 }

src/Neon/Node/EntityChainNode.php

@@ -48,6 +48,10 @@ public function toString(callable $serializer = null): string
 
 	public function getSubNodes(): array
 	{
-		return $this->chain;
+		$res = [];
+		foreach ($this->chain as &$item) {
+			$res[] = &$item;
+		}
+		return $res;
 	}
 }

src/Neon/Node/EntityNode.php

@@ -52,6 +52,10 @@ public function toString(callable $serializer = null): string
 
 	public function getSubNodes(): array
 	{
-		return array_merge([$this->value], $this->attributes);
+		$res = [&$this->value];
+		foreach ($this->attributes as &$item) {
+			$res[] = &$item;
+		}
+		return $res;
 	}
 }

src/Neon/Traverser.php

@@ -13,11 +13,11 @@
 /** @internal */
 final class Traverser
 {
-	/** @var callable(Node): void */
+	/** @var callable(Node): ?Node */
 	private $callback;
 
 
-	/** @param  callable(Node): void  $callback */
+	/** @param  callable(Node): ?Node  $callback */
 	public function traverse(Node $node, callable $callback): Node
 	{
 		$this->callback = $callback;
@@ -27,9 +27,9 @@ public function traverse(Node $node, callable $callback): Node
 
 	private function traverseNode(Node $node): Node
 	{
-		($this->callback)($node);
-		foreach ($node->getSubNodes() as $subnode) {
-			$this->traverseNode($subnode);
+		$node = ($this->callback)($node) ?? $node;
+		foreach ($node->getSubNodes() as &$subnode) {
+			$subnode = $this->traverseNode($subnode);
 		}
 		return $node;
 	}

tests/Neon/Traverser.alter.phpt

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+use Nette\Neon;
+use Nette\Neon\Node;
+use Tester\Assert;
+
+
+require __DIR__ . '/../bootstrap.php';
+
+$visitor = function (Node $node) {
+	return clone $node;
+};
+
+$decoder = new Neon\Decoder;
+$node = $decoder->parseToNode('
+a: foo(1, 2, 3)
+');
+
+$traverser = new Neon\Traverser;
+$newNode = $traverser->traverse($node, $visitor);
+
+Assert::equal($node, $newNode);
+Assert::notSame($node, $newNode);
+
+Assert::equal($node->items[0], $newNode->items[0]);
+Assert::notSame($node->items[0], $newNode->items[0]);
+
+Assert::equal($node->items[0]->key, $newNode->items[0]->key);
+Assert::notSame($node->items[0]->key, $newNode->items[0]->key);
+
+Assert::equal($node->items[0]->value, $newNode->items[0]->value);
+Assert::notSame($node->items[0]->value, $newNode->items[0]->value);
+
+Assert::equal($node->items[0]->value->value, $newNode->items[0]->value->value);
+Assert::notSame($node->items[0]->value->value, $newNode->items[0]->value->value);
+
+Assert::equal($node->items[0]->value->attributes[0], $newNode->items[0]->value->attributes[0]);
+Assert::notSame($node->items[0]->value->attributes[0], $newNode->items[0]->value->attributes[0]);