CachingIterator: do not ask when not in valid state (#230)

src/Latte/Runtime/CachingIterator.php

@@ -156,22 +156,24 @@ public function rewind(): void
 
 
 	/**
-	 * Returns the next key.
+	 * Returns the next key or null if position is not valid.
 	 * @return mixed
 	 */
 	public function getNextKey()
 	{
-		return $this->getInnerIterator()->key();
+		$iterator = $this->getInnerIterator();
+		return $iterator->valid() ? $iterator->key() : null;
 	}
 
 
 	/**
-	 * Returns the next element.
+	 * Returns the next element or null if position is not valid.
 	 * @return mixed
 	 */
 	public function getNextValue()
 	{
-		return $this->getInnerIterator()->current();
+		$iterator = $this->getInnerIterator();
+		return $iterator->valid() ? $iterator->current() : null;
 	}
 
 

tests/Latte/CachingIterator.basic.phpt

@@ -73,3 +73,40 @@ test('', function () {
 	Assert::same(0, $iterator->getCounter());
 	Assert::true($iterator->isEmpty());
 });
+
+test('Check if next position is valid', function () {
+	// empty iterator
+	$inner = new class implements Iterator {
+		public function current()
+		{
+			throw new RuntimeException('Invalid state');
+		}
+
+
+		public function next(): void
+		{
+		}
+
+
+		public function key()
+		{
+			throw new RuntimeException('Invalid state');
+		}
+
+
+		public function valid(): bool
+		{
+			return false;
+		}
+
+
+		public function rewind(): void
+		{
+		}
+	};
+
+	$iterator = new CachingIterator($inner);
+	$iterator->rewind();
+	Assert::null($iterator->nextKey);
+	Assert::null($iterator->nextValue);
+});