avoid infinite loop when all steps are skipped

Exception/AllStepsSkippedException.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Craue\FormFlowBundle\Exception;
+
+/**
+ * @author Christian Raue <christian.raue@gmail.com>
+ * @copyright 2011-2020 Christian Raue
+ * @license http://opensource.org/licenses/mit-license.php MIT License
+ */
+class AllStepsSkippedException extends \RuntimeException {
+
+	public function __construct() {
+		parent::__construct('All steps are marked as skipped. Please check the flow to make sure at least one step is not skipped.');
+	}
+
+}

Form/FormFlow.php

@@ -11,6 +11,7 @@
 use Craue\FormFlowBundle\Event\PostValidateEvent;
 use Craue\FormFlowBundle\Event\PreBindEvent;
 use Craue\FormFlowBundle\Event\PreviousStepInvalidEvent;
+use Craue\FormFlowBundle\Exception\AllStepsSkippedException;
 use Craue\FormFlowBundle\Exception\InvalidTypeException;
 use Craue\FormFlowBundle\Storage\DataManagerInterface;
 use Craue\FormFlowBundle\Util\StringUtil;
@@ -429,10 +430,11 @@ public function isStepSkipped($stepNumber) {
 	/**
 	 * @param int $stepNumber Assumed step to which skipped steps shall be applied to.
 	 * @param int $direction Either 1 (to skip forwards) or -1 (to skip backwards).
+	 * @param int $boundsReached Internal counter to avoid endlessly bouncing back and forth.
 	 * @return int Target step number with skipping applied.
 	 * @throws \InvalidArgumentException If the value of <code>$direction</code> is invalid.
 	 */
-	protected function applySkipping($stepNumber, $direction = 1) {
+	protected function applySkipping($stepNumber, $direction = 1, $boundsReached = 0) {
 		if ($direction !== 1 && $direction !== -1) {
 			throw new \InvalidArgumentException(sprintf('Argument of either -1 or 1 expected, "%s" given.', $direction));
 		}
@@ -445,11 +447,17 @@ protected function applySkipping($stepNumber, $direction = 1) {
 			// change direction if outer bounds are reached
 			if ($direction === 1 && $stepNumber > $this->getStepCount()) {
 				$direction = -1;
+				++$boundsReached;
 			} elseif ($direction === -1 && $stepNumber < 1) {
 				$direction = 1;
+				++$boundsReached;
 			}
 
-			return $this->applySkipping($stepNumber, $direction);
+			if ($boundsReached > 2) {
+				throw new AllStepsSkippedException();
+			}
+
+			return $this->applySkipping($stepNumber, $direction, $boundsReached);
 		}
 
 		return $stepNumber;

Tests/Form/FormFlowTest.php

@@ -673,6 +673,29 @@ public function dataApplySkipping_invalidArguments() {
 		];
 	}
 
+	/**
+	 * @expectedException Craue\FormFlowBundle\Exception\AllStepsSkippedException
+	 * @expectedExceptionMessage All steps are marked as skipped. Please check the flow to make sure at least one step is not skipped.
+	 */
+	public function testApplySkipping_bouncing() {
+		$flow = $this->getFlowWithMockedMethods(['loadStepsConfig']);
+
+		$flow
+			->expects($this->once())
+			->method('loadStepsConfig')
+			->will($this->returnValue([
+				[
+					'skip' => true,
+				],
+			]))
+		;
+
+		$method = new \ReflectionMethod($flow, 'applySkipping');
+		$method->setAccessible(true);
+
+		$method->invoke($flow, 1);
+	}
+
 	/**
 	 * @dataProvider dataGetStep_invalidArguments
 	 * @expectedException \Craue\FormFlowBundle\Exception\InvalidTypeException