symfony · d-ph · Oct 29, 2017 · Oct 29, 2017 · Oct 29, 2017 · Oct 29, 2017
diff --git a/src/Symfony/Component/Workflow/CHANGELOG.md b/src/Symfony/Component/Workflow/CHANGELOG.md
@@ -8,6 +8,8 @@ CHANGELOG
  * Deprecate the usage of `SupportStrategyInterface`, use `WorkflowSupportStrategyInterface` instead.
  * The `Workflow` class now implements `WorkflowInterface`.
  * Deprecated the class `ClassInstanceSupportStrategy` in favor of the class `InstanceOfSupportStrategy`.
+ * Added TransitionBlockers as a way to pass around reasons why exactly transitions 
+   can't be made.
 
 4.0.0
 -----

diff --git a/src/Symfony/Component/Workflow/Event/GuardEvent.php b/src/Symfony/Component/Workflow/Event/GuardEvent.php
@@ -11,21 +11,52 @@
 
 namespace Symfony\Component\Workflow\Event;
 
+use Symfony\Component\Workflow\Marking;
+use Symfony\Component\Workflow\Transition;
+use Symfony\Component\Workflow\TransitionBlocker;
+use Symfony\Component\Workflow\TransitionBlockerList;
+
 /**
  * @author Fabien Potencier <fabien@symfony.com>
  * @author Grégoire Pineau <lyrixx@lyrixx.info>
  */
 class GuardEvent extends Event
 {
-    private $blocked = false;
+    private $transitionBlockerList;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function __construct($subject, Marking $marking, Transition $transition, $workflowName = 'unnamed')
+    {
+        parent::__construct($subject, $marking, $transition, $workflowName);
+
+        $this->transitionBlockerList = new TransitionBlockerList();
+    }
+
+    public function isBlocked(): bool
+    {
+        return 0 !== count($this->transitionBlockerList);
+    }
+
+    public function setBlocked(bool $blocked): void
+    {
+        if (!$blocked) {
+            $this->transitionBlockerList = new TransitionBlockerList();
+
+            return;
+        }
+
+        $this->transitionBlockerList->add(TransitionBlocker::createUnknownReason($this->getTransition()->getName()));
+    }
 
-    public function isBlocked()
+    public function getTransitionBlockerList(): TransitionBlockerList
     {
-        return $this->blocked;
+        return $this->transitionBlockerList;
     }
 
-    public function setBlocked($blocked)
+    public function addTransitionBlocker(TransitionBlocker $transitionBlocker): void
     {
-        $this->blocked = (bool) $blocked;
+        $this->transitionBlockerList->add($transitionBlocker);
     }
 }
diff --git a/src/Symfony/Component/Workflow/Exception/BlockedTransitionException.php b/src/Symfony/Component/Workflow/Exception/BlockedTransitionException.php
@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Workflow\Exception;
+
+use Symfony\Component\Workflow\TransitionBlockerList;
+
+/**
+ * Thrown by the workflow when a transition is not enabled.
+ */
+class BlockedTransitionException extends LogicException
+{
+    private $transitionBlockerList;
+
+    public function __construct(string $message, TransitionBlockerList $transitionBlockerList)
+    {
+        parent::__construct($message);
+
+        $this->transitionBlockerList = $transitionBlockerList;
+    }
+
+    public function getTransitionBlockerList(): TransitionBlockerList
+    {
+        return $this->transitionBlockerList;
+    }
+}
diff --git a/src/Symfony/Component/Workflow/Exception/UndefinedTransitionException.php b/src/Symfony/Component/Workflow/Exception/UndefinedTransitionException.php
@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Workflow\Exception;
+
+/**
+ * Thrown by Workflow when an undefined transition is applied on a subject.
+ */
+class UndefinedTransitionException extends LogicException
+{
+}
diff --git a/src/Symfony/Component/Workflow/Tests/WorkflowTest.php b/src/Symfony/Component/Workflow/Tests/WorkflowTest.php
@@ -7,10 +7,12 @@
 use Symfony\Component\Workflow\Definition;
 use Symfony\Component\Workflow\Event\Event;
 use Symfony\Component\Workflow\Event\GuardEvent;
+use Symfony\Component\Workflow\Exception\BlockedTransitionException;
 use Symfony\Component\Workflow\Marking;
 use Symfony\Component\Workflow\MarkingStore\MarkingStoreInterface;
 use Symfony\Component\Workflow\MarkingStore\MultipleStateMarkingStore;
 use Symfony\Component\Workflow\Transition;
+use Symfony\Component\Workflow\TransitionBlocker;
 use Symfony\Component\Workflow\Workflow;
 
 class WorkflowTest extends TestCase
@@ -411,6 +413,116 @@ public function testGetEnabledTransitionsWithSameNameTransition()
         $this->assertSame('to_a', $transitions[1]->getName());
         $this->assertSame('to_a', $transitions[2]->getName());
     }
+
+    public function testWhyCannotReturnsReasonsProvidedInGuards()
+    {
+        $definition = $this->createSimpleWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+        $dispatcher = new EventDispatcher();
+        $workflow = new Workflow($definition, new MultipleStateMarkingStore(), $dispatcher);
+
+        $guardsAddingTransitionBlockers = array(
+            function (GuardEvent $event) {
+                $event->addTransitionBlocker(new TransitionBlocker('Transition blocker 1', 'blocker_1'));
+                $event->addTransitionBlocker(new TransitionBlocker('Transition blocker 2', 'blocker_2'));
+            },
+            function (GuardEvent $event) {
+                $event->addTransitionBlocker(new TransitionBlocker('Transition blocker 3', 'blocker_3'));
+            },
+        );
+
+        foreach ($guardsAddingTransitionBlockers as $guard) {
+            $dispatcher->addListener('workflow.guard', $guard);
+        }
+
+        $transitionBlockerList = $workflow->buildTransitionBlockerList($subject, 't1');
+
+        $this->assertCount(3, $transitionBlockerList);
+
+        $assertTransitionBlockerPresentByCodeFn = function (string $code) use ($transitionBlockerList) {
+            $this->assertNotNull(
+                $transitionBlockerList->findByCode($code),
+                sprintf('Workflow did not produce transition blocker with code "%s"', $code)
+            );
+        };
+
+        $assertTransitionBlockerPresentByCodeFn('blocker_1');
+        $assertTransitionBlockerPresentByCodeFn('blocker_2');
+        $assertTransitionBlockerPresentByCodeFn('blocker_3');
+    }
+
+    public function testWhyCannotReturnsTransitionNotDefinedReason()
+    {
+        $definition = $this->createSimpleWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+        $workflow = new Workflow($definition);
+
+        $transitionBlockerList = $workflow->buildTransitionBlockerList($subject, 'undefined_transition_name');
+
+        $this->assertCount(1, $transitionBlockerList);
+        $this->assertEquals(
+            TransitionBlocker::REASON_TRANSITION_NOT_DEFINED,
+            $transitionBlockerList->get(0)->getCode()
+        );
+    }
+
+    public function testWhyCannotReturnsTransitionNotApplicableReason()
+    {
+        $definition = $this->createSimpleWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+        $workflow = new Workflow($definition);
+
+        $transitionBlockerList = $workflow->buildTransitionBlockerList($subject, 't2');
+
+        $this->assertCount(1, $transitionBlockerList);
+        $this->assertEquals(
+            TransitionBlocker::REASON_TRANSITION_NOT_APPLICABLE,
+            $transitionBlockerList->get(0)->getCode()
+        );
+    }
+
+    public function testApplyConveysTheTransitionBlockers()
+    {
+        $definition = $this->createSimpleWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+        $dispatcher = new EventDispatcher();
+        $workflow = new Workflow($definition, new MultipleStateMarkingStore(), $dispatcher);
+
+        $dispatcher->addListener('workflow.guard', function (GuardEvent $event) {
+            $event->addTransitionBlocker(new TransitionBlocker('Transition blocker 3', 'blocker_1'));
+        });
+
+        try {
+            $workflow->apply($subject, 't1');
+        } catch (BlockedTransitionException $exception) {
+            $this->assertNotNull(
+                $exception->getTransitionBlockerList()->findByCode('blocker_1'),
+                'Workflow failed to convey it could not transition subject because of expected blocker'
+            );
+
+            return;
+        }
+
+        $this->fail('Workflow failed to prevent a transition from happening');
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Workflow\Exception\UndefinedTransitionException
+     * @expectedExceptionMessage Transition "undefined_transition" is not defined in workflow "unnamed".
+     */
+    public function testApplyWithUndefinedTransition()
+    {
+        $definition = $this->createSimpleWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+        $workflow = new Workflow($definition);
+
+        $workflow->apply($subject, 'undefined_transition');
+    }
 }
 
 class EventDispatcherMock implements \Symfony\Component\EventDispatcher\EventDispatcherInterface

diff --git a/src/Symfony/Component/Workflow/TransitionBlocker.php b/src/Symfony/Component/Workflow/TransitionBlocker.php
@@ -0,0 +1,112 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Workflow;
+
+/**
+ * A reason why a transition cannot be performed for a subject.
+ */
+class TransitionBlocker
+{
+    const REASON_TRANSITION_NOT_DEFINED = '80f2a8e9-ee53-408a-9dd8-cce09e031db8';
+    const REASON_TRANSITION_NOT_APPLICABLE = '19beefc8-6b1e-4716-9d07-a39bd6d16e34';
+    const REASON_TRANSITION_UNKNOWN = 'e8b5bbb9-5913-4b98-bfa6-65dbd228a82a';
+
+    private $message;
+    private $code;
+
+    /**
+     * @var array This is useful if you would like to pass around the condition values, that
+     *            blocked the transition. E.g. for a condition "distance must be larger than
+     *            5 miles", you might want to pass around the value of 5.
+     */
+    private $parameters;
+
+    public function __construct(string $message, string $code, array $parameters = array())
+    {
+        $this->message = $message;
+        $this->code = $code;
+        $this->parameters = $parameters;
+    }
+
+    /**
+     * Create a blocker, that says the transition cannot be made because it is undefined
+     * in a workflow.
+     *
+     * @param string $transitionName
+     * @param string $workflowName
+     *
+     * @return static
+     */
+    public static function createNotDefined(string $transitionName, string $workflowName): self
+    {
+        $message = sprintf('Transition "%s" is not defined in workflow "%s".', $transitionName, $workflowName);
+        $parameters = array(
+            'transitionName' => $transitionName,
+            'workflowName' => $workflowName,
+        );
+
+        return new static($message, self::REASON_TRANSITION_NOT_DEFINED, $parameters);
+    }
+
+    /**
+     * Create a blocker, that says the transition cannot be made because the subject
+     * is in wrong place (i.e. status).
+     *
+     * @param string $transitionName
+     *
+     * @return static
+     */
+    public static function createNotApplicable(string $transitionName): self
+    {
+        $message = sprintf('Transition "%s" cannot be made, because the subject is not in the required place.', $transitionName);
+        $parameters = array(
+            'transitionName' => $transitionName,
+        );
+
+        return new static($message, self::REASON_TRANSITION_NOT_APPLICABLE, $parameters);
+    }
+
+    /**
+     * Create a blocker, that says the transition cannot be made because of unknown
+     * reason.
+     *
+     * This blocker code is chiefly for preserving backwards compatibility.
+     *
+     * @param string $transitionName
+     *
+     * @return static
+     */
+    public static function createUnknownReason(string $transitionName): self
+    {
+        $message = sprintf('Transition "%s" cannot be made, because of unknown reason.', $transitionName);
+        $parameters = array(
+            'transitionName' => $transitionName,
+        );
+
+        return new static($message, self::REASON_TRANSITION_UNKNOWN, $parameters);
+    }
+
+    public function getMessage(): string
+    {
+        return $this->message;
+    }
+
+    public function getCode(): string
+    {
+        return $this->code;
+    }
+
+    public function getParameters(): array
+    {
+        return $this->parameters;
+    }
+}