feature #19629 [Workflow] Make the Workflow support State Machines (Nyholm, lyrixx)

This PR was merged into the 3.2-dev branch.

Discussion
----------

[Workflow] Make the Workflow support State Machines

| Q | A |
| --- | --- |
| Branch? | "master" |
| Bug fix? | no |
| New feature? | yes |
| BC breaks? | yes, getEnabledTransistions does not return an assoc array. |
| Deprecations? | no |
| Tests pass? | yes |
| Fixed tickets | Fixes #19605, Closes #19607 |
| License | MIT |
| Doc PR | https://github.com/symfony/symfony-docs/pull/6871 |

While researching for the docs of the component I've found that:
- A Workflow is a subclass of a Petri net
- A state machine is subclass of a Workflow
- A state machine must not be in many places simultaneously.

This PR adds a new interface to the marking store that allow us to validate the transition to true if ANY _input_ (froms) place matches the _tokens_ (marking). The default behavior is that ALL input places must match the tokens.

Commits
-------

9e49198 [Workflow] Made the code more robbust and ease on-boarding
bdd3f95 Make the Workflow support State Machines

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/ValidateWorkflowsPass.php

@@ -0,0 +1,77 @@
+<?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\Bundle\FrameworkBundle\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+use Symfony\Component\Workflow\Validator\DefinitionValidatorInterface;
+use Symfony\Component\Workflow\Validator\SinglePlaceWorkflowValidator;
+use Symfony\Component\Workflow\Validator\StateMachineValidator;
+use Symfony\Component\Workflow\Validator\WorkflowValidator;
+
+/**
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class ValidateWorkflowsPass implements CompilerPassInterface
+{
+    /**
+     * @var DefinitionValidatorInterface[]
+     */
+    private $validators = array();
+
+    public function process(ContainerBuilder $container)
+    {
+        $taggedServices = $container->findTaggedServiceIds('workflow.definition');
+        foreach ($taggedServices as $id => $tags) {
+            $definition = $container->get($id);
+            foreach ($tags as $tag) {
+                if (!array_key_exists('name', $tag)) {
+                    throw new RuntimeException(sprintf('The "name" for the tag "workflow.definition" of service "%s" must be set.', $id));
+                }
+                if (!array_key_exists('type', $tag)) {
+                    throw new RuntimeException(sprintf('The "type" for the tag "workflow.definition" of service "%s" must be set.', $id));
+                }
+                if (!array_key_exists('marking_store', $tag)) {
+                    throw new RuntimeException(sprintf('The "marking_store" for the tag "workflow.definition" of service "%s" must be set.', $id));
+                }
+
+                $this->getValidator($tag)->validate($definition, $tag['name']);
+            }
+        }
+    }
+
+    /**
+     * @param array $tag
+     *
+     * @return DefinitionValidatorInterface
+     */
+    private function getValidator($tag)
+    {
+        if ($tag['type'] === 'state_machine') {
+            $name = 'state_machine';
+            $class = StateMachineValidator::class;
+        } elseif ($tag['marking_store'] === 'scalar') {
+            $name = 'single_place';
+            $class = SinglePlaceWorkflowValidator::class;
+        } else {
+            $name = 'workflow';
+            $class = WorkflowValidator::class;
+        }
+
+        if (empty($this->validators[$name])) {
+            $this->validators[$name] = new $class();
+        }
+
+        return $this->validators[$name];
+    }
+}

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php

@@ -236,6 +236,10 @@ class Configuration implements ConfigurationInterface
                     ->useAttributeAsKey('name')
                     ->prototype('array')
                         ->children()
+                            ->enumNode('type')
+                                ->values(array('workflow', 'state_machine'))
+                                ->defaultValue('workflow')
+                            ->end()
                             ->arrayNode('marking_store')
                                 ->isRequired()
                                 ->children()

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -404,10 +404,20 @@ class FrameworkExtension extends Extension
         $registryDefinition = $container->getDefinition('workflow.registry');
 
         foreach ($workflows as $name => $workflow) {
+            $type = $workflow['type'];
+
             $definitionDefinition = new Definition(Workflow\Definition::class);
             $definitionDefinition->addMethodCall('addPlaces', array($workflow['places']));
             foreach ($workflow['transitions'] as $transitionName => $transition) {
-                $definitionDefinition->addMethodCall('addTransition', array(new Definition(Workflow\Transition::class, array($transitionName, $transition['from'], $transition['to']))));
+                if ($type === 'workflow') {
+                    $definitionDefinition->addMethodCall('addTransition', array(new Definition(Workflow\Transition::class, array($transitionName, $transition['from'], $transition['to']))));
+                } elseif ($type === 'state_machine') {
+                    foreach ($transition['from'] as $from) {
+                        foreach ($transition['to'] as $to) {
+                            $definitionDefinition->addMethodCall('addTransition', array(new Definition(Workflow\Transition::class, array($transitionName, $from, $to))));
+                        }
+                    }
+                }
             }
 
             if (isset($workflow['marking_store']['type'])) {
@@ -415,17 +425,27 @@ class FrameworkExtension extends Extension
                 foreach ($workflow['marking_store']['arguments'] as $argument) {
                     $markingStoreDefinition->addArgument($argument);
                 }
-            } else {
+            } elseif (isset($workflow['marking_store']['service'])) {
                 $markingStoreDefinition = new Reference($workflow['marking_store']['service']);
             }
 
-            $workflowDefinition = new DefinitionDecorator('workflow.abstract');
+            $definitionDefinition->addTag('workflow.definition', array(
+                'name' => $name,
+                'type' => $type,
+                'marking_store' => isset($workflow['marking_store']['type']) ? $workflow['marking_store']['type'] : null,
+            ));
+            $definitionDefinition->setPublic(false);
+
+            $workflowDefinition = new DefinitionDecorator(sprintf('%s.abstract', $type));
             $workflowDefinition->replaceArgument(0, $definitionDefinition);
-            $workflowDefinition->replaceArgument(1, $markingStoreDefinition);
+            if (isset($markingStoreDefinition)) {
+                $workflowDefinition->replaceArgument(1, $markingStoreDefinition);
+            }
             $workflowDefinition->replaceArgument(3, $name);
 
-            $workflowId = 'workflow.'.$name;
+            $workflowId = sprintf('%s.%s', $type, $name);
 
+            $container->setDefinition(sprintf('%s.definition', $workflowId), $definitionDefinition);
             $container->setDefinition($workflowId, $workflowDefinition);
 
             foreach ($workflow['supports'] as $supportedClass) {

src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php

@@ -35,6 +35,7 @@ use Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\TranslationDumpe
 use Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\SerializerPass;
 use Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\UnusedTagsPass;
 use Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\ConfigCachePass;
+use Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\ValidateWorkflowsPass;
 use Symfony\Component\Debug\ErrorHandler;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Compiler\PassConfig;
@@ -93,6 +94,7 @@ class FrameworkBundle extends Bundle
         $container->addCompilerPass(new PropertyInfoPass());
         $container->addCompilerPass(new ControllerArgumentValueResolverPass());
         $container->addCompilerPass(new CachePoolPass());
+        $container->addCompilerPass(new ValidateWorkflowsPass());
         $container->addCompilerPass(new CachePoolClearerPass(), PassConfig::TYPE_AFTER_REMOVING);
 
         if ($container->getParameter('kernel.debug')) {

src/Symfony/Bundle/FrameworkBundle/Resources/config/workflow.xml

@@ -7,7 +7,13 @@
     <services>
         <service id="workflow.abstract" class="Symfony\Component\Workflow\Workflow" abstract="true">
             <argument /> <!-- workflow definition -->
-            <argument /> <!-- marking store -->
+            <argument type="constant">null</argument> <!-- marking store -->
+            <argument type="service" id="event_dispatcher" on-invalid="ignore" />
+            <argument /> <!-- name -->
+        </service>
+        <service id="state_machine.abstract" class="Symfony\Component\Workflow\StateMachine" abstract="true">
+            <argument /> <!-- workflow definition -->
+            <argument type="constant">null</argument> <!-- marking store -->
             <argument type="service" id="event_dispatcher" on-invalid="ignore" />
             <argument /> <!-- name -->
         </service>

src/Symfony/Component/Workflow/Definition.php

@@ -46,6 +46,9 @@ class Definition
         return $this->places;
     }
 
+    /**
+     * @return Transition[]
+     */
     public function getTransitions()
     {
         return $this->transitions;
@@ -103,6 +106,6 @@ class Definition
             }
         }
 
-        $this->transitions[$name] = $transition;
+        $this->transitions[] = $transition;
     }
 }

src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php

@@ -83,9 +83,10 @@ class GraphvizDumper implements DumperInterface
     {
         $transitions = array();
 
-        foreach ($definition->getTransitions() as $name => $transition) {
-            $transitions[$name] = array(
+        foreach ($definition->getTransitions() as $transition) {
+            $transitions[] = array(
                 'attributes' => array('shape' => 'box', 'regular' => true),
+                'name' => $transition->getName(),
             );
         }
 
@@ -111,10 +112,10 @@ class GraphvizDumper implements DumperInterface
     {
         $code = '';
 
-        foreach ($transitions as $id => $place) {
+        foreach ($transitions as $place) {
             $code .= sprintf("  transition_%s [label=\"%s\", shape=box%s];\n",
-                $this->dotize($id),
-                $id,
+                $this->dotize($place['name']),
+                $place['name'],
                 $this->addAttributes($place['attributes'])
             );
         }

src/Symfony/Component/Workflow/Exception/InvalidDefinitionException.php

@@ -0,0 +1,21 @@
+<?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 the DefinitionValidatorInterface when the definition is invalid.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class InvalidDefinitionException extends \LogicException implements ExceptionInterface
+{
+}

src/Symfony/Component/Workflow/MarkingStore/ScalarMarkingStore.php

@@ -20,7 +20,7 @@ use Symfony\Component\Workflow\Marking;
  *
  * @author Grégoire Pineau <lyrixx@lyrixx.info>
  */
-class ScalarMarkingStore implements MarkingStoreInterface, UniqueTransitionOutputInterface
+class ScalarMarkingStore implements MarkingStoreInterface
 {
     private $property;
     private $propertyAccessor;

src/Symfony/Component/Workflow/MarkingStore/UniqueTransitionOutputInterface.php

@@ -1,21 +0,0 @@
-<?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\MarkingStore;
-
-/**
- * UniqueTransitionOutputInterface.
- *
- * @author Grégoire Pineau <lyrixx@lyrixx.info>
- */
-interface UniqueTransitionOutputInterface
-{
-}

src/Symfony/Component/Workflow/StateMachine.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Symfony\Component\Workflow;
+
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\Workflow\MarkingStore\MarkingStoreInterface;
+use Symfony\Component\Workflow\MarkingStore\ScalarMarkingStore;
+
+/**
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class StateMachine extends Workflow
+{
+    public function __construct(Definition $definition, MarkingStoreInterface $markingStore = null, EventDispatcherInterface $dispatcher = null, $name = 'unnamed')
+    {
+        parent::__construct($definition, $markingStore ?: new ScalarMarkingStore(), $dispatcher, $name);
+    }
+}

src/Symfony/Component/Workflow/Tests/DefinitionTest.php

@@ -55,7 +55,7 @@ class DefinitionTest extends \PHPUnit_Framework_TestCase
         $definition = new Definition($places, array($transition));
 
         $this->assertCount(1, $definition->getTransitions());
-        $this->assertSame($transition, $definition->getTransitions()['name']);
+        $this->assertSame($transition, $definition->getTransitions()[0]);
     }
 
     /**

src/Symfony/Component/Workflow/Tests/RegistryTest.php

@@ -18,9 +18,9 @@ class RegistryTest extends \PHPUnit_Framework_TestCase
 
         $this->registry = new Registry();
 
-        $this->registry->add(new Workflow(new Definition(), $this->getMock(MarkingStoreInterface::class), $this->getMock(EventDispatcherInterface::class), 'workflow1'), Subject1::class);
-        $this->registry->add(new Workflow(new Definition(), $this->getMock(MarkingStoreInterface::class), $this->getMock(EventDispatcherInterface::class), 'workflow2'), Subject2::class);
-        $this->registry->add(new Workflow(new Definition(), $this->getMock(MarkingStoreInterface::class), $this->getMock(EventDispatcherInterface::class), 'workflow3'), Subject2::class);
+        $this->registry->add(new Workflow(new Definition(), $this->getMockBuilder(MarkingStoreInterface::class)->getMock(), $this->getMockBuilder(EventDispatcherInterface::class)->getMock(), 'workflow1'), Subject1::class);
+        $this->registry->add(new Workflow(new Definition(), $this->getMockBuilder(MarkingStoreInterface::class)->getMock(), $this->getMockBuilder(EventDispatcherInterface::class)->getMock(), 'workflow2'), Subject2::class);
+        $this->registry->add(new Workflow(new Definition(), $this->getMockBuilder(MarkingStoreInterface::class)->getMock(), $this->getMockBuilder(EventDispatcherInterface::class)->getMock(), 'workflow3'), Subject2::class);
     }
 
     protected function tearDown()
@@ -55,7 +55,7 @@ class RegistryTest extends \PHPUnit_Framework_TestCase
     }
 
     /**
-     * @expectedException Symfony\Component\Workflow\Exception\InvalidArgumentException
+     * @expectedException \Symfony\Component\Workflow\Exception\InvalidArgumentException
      * @expectedExceptionMessage Unable to find a workflow for class "stdClass".
      */
     public function testGetWithNoMatch()

src/Symfony/Component/Workflow/Tests/StateMachineTest.php

@@ -0,0 +1,75 @@
+<?php
+
+namespace Symfony\Component\Workflow\Tests;
+
+use Symfony\Component\Workflow\Definition;
+use Symfony\Component\Workflow\Marking;
+use Symfony\Component\Workflow\StateMachine;
+use Symfony\Component\Workflow\Transition;
+
+class StateMachineTest extends \PHPUnit_Framework_TestCase
+{
+    public function testCan()
+    {
+        $places = array('a', 'b', 'c', 'd');
+        $transitions[] = new Transition('t1', 'a', 'b');
+        $transitions[] = new Transition('t1', 'd', 'b');
+        $transitions[] = new Transition('t2', 'b', 'c');
+        $transitions[] = new Transition('t3', 'b', 'd');
+        $definition = new Definition($places, $transitions);
+
+        $net = new StateMachine($definition);
+        $subject = new \stdClass();
+
+        // If you are in place "a" you should be able to apply "t1"
+        $subject->marking = 'a';
+        $this->assertTrue($net->can($subject, 't1'));
+        $subject->marking = 'd';
+        $this->assertTrue($net->can($subject, 't1'));
+
+        $subject->marking = 'b';
+        $this->assertFalse($net->can($subject, 't1'));
+
+        // The graph looks like:
+        //
+        //                        +-------------------------------+
+        //                        v                               |
+        // +---+     +----+     +----+     +----+     +---+     +----+
+        // | a | --> | t1 | --> | b  | --> | t3 | --> | d | --> | t1 |
+        // +---+     +----+     +----+     +----+     +---+     +----+
+        //                        |
+        //                        |
+        //                        v
+        //                      +----+     +----+
+        //                      | t2 | --> | c  |
+        //                      +----+     +----+
+    }
+
+    public function testCanWithMultipleTransition()
+    {
+        $places = array('a', 'b', 'c');
+        $transitions[] = new Transition('t1', 'a', 'b');
+        $transitions[] = new Transition('t2', 'a', 'c');
+        $definition = new Definition($places, $transitions);
+
+        $net = new StateMachine($definition);
+        $subject = new \stdClass();
+
+        // If you are in place "a" you should be able to apply "t1" and "t2"
+        $subject->marking = 'a';
+        $this->assertTrue($net->can($subject, 't1'));
+        $this->assertTrue($net->can($subject, 't2'));
+
+        // The graph looks like:
+        //
+        // +----+     +----+     +---+
+        // | a  | --> | t1 | --> | b |
+        // +----+     +----+     +---+
+        //   |
+        //   |
+        //   v
+        // +----+     +----+
+        // | t2 | --> | c  |
+        // +----+     +----+
+    }
+}

src/Symfony/Component/Workflow/Tests/Validator/SinglePlaceWorkflowValidatorTest.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Symfony\Component\Workflow\Tests\Validator;
+
+use Symfony\Component\Workflow\Definition;
+use Symfony\Component\Workflow\Marking;
+use Symfony\Component\Workflow\Tests\WorkflowTest;
+use Symfony\Component\Workflow\Transition;
+use Symfony\Component\Workflow\Validator\SinglePlaceWorkflowValidator;
+use Symfony\Component\Workflow\Workflow;
+
+class SinglePlaceWorkflowValidatorTest extends WorkflowTest
+{
+    /**
+     * @expectedException \Symfony\Component\Workflow\Exception\InvalidDefinitionException
+     * @expectedExceptionMessage The marking store of workflow "foo" can not store many places.
+     */
+    public function testSinglePlaceWorkflowValidatorAndComplexWorkflow()
+    {
+        $definition = $this->createComplexWorkflow();
+
+        (new SinglePlaceWorkflowValidator())->validate($definition, 'foo');
+    }
+
+    public function testSinglePlaceWorkflowValidatorAndSimpleWorkflow()
+    {
+        $places = array('a', 'b');
+        $transition = new Transition('t1', 'a', 'b');
+        $definition = new Definition($places, array($transition));
+
+        (new SinglePlaceWorkflowValidator())->validate($definition, 'foo');
+    }
+}

src/Symfony/Component/Workflow/Tests/Validator/StateMachineValidatorTest.php

@@ -0,0 +1,108 @@
+<?php
+
+namespace Symfony\Component\Workflow\Tests\Validator;
+
+use Symfony\Component\Workflow\Definition;
+use Symfony\Component\Workflow\Transition;
+use Symfony\Component\Workflow\Validator\StateMachineValidator;
+
+class StateMachineValidatorTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @expectedException \Symfony\Component\Workflow\Exception\InvalidDefinitionException
+     * @expectedExceptionMessage A transition from a place/state must have an unique name.
+     */
+    public function testWithMultipleTransitionWithSameNameShareInput()
+    {
+        $places = array('a', 'b', 'c');
+        $transitions[] = new Transition('t1', 'a', 'b');
+        $transitions[] = new Transition('t1', 'a', 'c');
+        $definition = new Definition($places, $transitions);
+
+        (new StateMachineValidator())->validate($definition, 'foo');
+
+        // The graph looks like:
+        //
+        //   +----+     +----+     +---+
+        //   | a  | --> | t1 | --> | b |
+        //   +----+     +----+     +---+
+        //    |
+        //    |
+        //    v
+        //  +----+     +----+
+        //  | t1 | --> | c  |
+        //  +----+     +----+
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Workflow\Exception\InvalidDefinitionException
+     * @expectedExceptionMessage A transition in StateMachine can only have one output.
+     */
+    public function testWithMultipleTos()
+    {
+        $places = array('a', 'b', 'c');
+        $transitions[] = new Transition('t1', 'a', array('b', 'c'));
+        $definition = new Definition($places, $transitions);
+
+        (new StateMachineValidator())->validate($definition, 'foo');
+
+        // The graph looks like:
+        //
+        // +---+     +----+     +---+
+        // | a | --> | t1 | --> | b |
+        // +---+     +----+     +---+
+        //             |
+        //             |
+        //             v
+        //           +----+
+        //           | c  |
+        //           +----+
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Workflow\Exception\InvalidDefinitionException
+     * @expectedExceptionMessage A transition in StateMachine can only have one input.
+     */
+    public function testWithMultipleFroms()
+    {
+        $places = array('a', 'b', 'c');
+        $transitions[] = new Transition('t1', array('a', 'b'), 'c');
+        $definition = new Definition($places, $transitions);
+
+        (new StateMachineValidator())->validate($definition, 'foo');
+
+        // The graph looks like:
+        //
+        // +---+     +----+     +---+
+        // | a | --> | t1 | --> | c |
+        // +---+     +----+     +---+
+        //             ^
+        //             |
+        //             |
+        //           +----+
+        //           | b  |
+        //           +----+
+    }
+
+    public function testValid()
+    {
+        $places = array('a', 'b', 'c');
+        $transitions[] = new Transition('t1', 'a', 'b');
+        $transitions[] = new Transition('t2', 'a', 'c');
+        $definition = new Definition($places, $transitions);
+
+        (new StateMachineValidator())->validate($definition, 'foo');
+
+        // The graph looks like:
+        //
+        // +----+     +----+     +---+
+        // | a  | --> | t1 | --> | b |
+        // +----+     +----+     +---+
+        //   |
+        //   |
+        //   v
+        // +----+     +----+
+        // | t2 | --> | c  |
+        // +----+     +----+
+    }
+}

src/Symfony/Component/Workflow/Tests/WorkflowTest.php

@@ -8,32 +8,11 @@ use Symfony\Component\Workflow\Event\GuardEvent;
 use Symfony\Component\Workflow\Marking;
 use Symfony\Component\Workflow\MarkingStore\MarkingStoreInterface;
 use Symfony\Component\Workflow\MarkingStore\PropertyAccessorMarkingStore;
-use Symfony\Component\Workflow\MarkingStore\ScalarMarkingStore;
 use Symfony\Component\Workflow\Transition;
 use Symfony\Component\Workflow\Workflow;
 
 class WorkflowTest extends \PHPUnit_Framework_TestCase
 {
-    /**
-     * @expectedException \Symfony\Component\Workflow\Exception\LogicException
-     * @expectedExceptionMessage The marking store (Symfony\Component\Workflow\MarkingStore\ScalarMarkingStore) of workflow "unnamed" can not store many places. But the transition "t1" has too many output (2). Only one is accepted.
-     */
-    public function testConstructorWithUniqueTransitionOutputInterfaceAndComplexWorkflow()
-    {
-        $definition = $this->createComplexWorkflow();
-
-        new Workflow($definition, new ScalarMarkingStore());
-    }
-
-    public function testConstructorWithUniqueTransitionOutputInterfaceAndSimpleWorkflow()
-    {
-        $places = array('a', 'b');
-        $transition = new Transition('t1', 'a', 'b');
-        $definition = new Definition($places, array($transition));
-
-        new Workflow($definition, new ScalarMarkingStore());
-    }
-
     /**
      * @expectedException \Symfony\Component\Workflow\Exception\LogicException
      * @expectedExceptionMessage The value returned by the MarkingStore is not an instance of "Symfony\Component\Workflow\Marking" for workflow "unnamed".
@@ -42,7 +21,7 @@ class WorkflowTest extends \PHPUnit_Framework_TestCase
     {
         $subject = new \stdClass();
         $subject->marking = null;
-        $workflow = new Workflow(new Definition(), $this->getMock(MarkingStoreInterface::class));
+        $workflow = new Workflow(new Definition(), $this->getMockBuilder(MarkingStoreInterface::class)->getMock());
 
         $workflow->getMarking($subject);
     }
@@ -134,7 +113,9 @@ class WorkflowTest extends \PHPUnit_Framework_TestCase
         $subject = new \stdClass();
         $subject->marking = null;
         $eventDispatcher = new EventDispatcher();
-        $eventDispatcher->addListener('workflow.workflow_name.guard.t1', function (GuardEvent $event) { $event->setBlocked(true); });
+        $eventDispatcher->addListener('workflow.workflow_name.guard.t1', function (GuardEvent $event) {
+            $event->setBlocked(true);
+        });
         $workflow = new Workflow($definition, new PropertyAccessorMarkingStore(), $eventDispatcher, 'workflow_name');
 
         $this->assertFalse($workflow->can($subject, 't1'));
@@ -209,7 +190,9 @@ class WorkflowTest extends \PHPUnit_Framework_TestCase
         $subject = new \stdClass();
         $subject->marking = null;
         $eventDispatcher = new EventDispatcher();
-        $eventDispatcher->addListener('workflow.workflow_name.guard.t1', function (GuardEvent $event) { $event->setBlocked(true); });
+        $eventDispatcher->addListener('workflow.workflow_name.guard.t1', function (GuardEvent $event) {
+            $event->setBlocked(true);
+        });
         $workflow = new Workflow($definition, new PropertyAccessorMarkingStore(), $eventDispatcher, 'workflow_name');
 
         $this->assertEmpty($workflow->getEnabledTransitions($subject));
@@ -217,16 +200,16 @@ class WorkflowTest extends \PHPUnit_Framework_TestCase
         $subject->marking = array('d' => true);
         $transitions = $workflow->getEnabledTransitions($subject);
         $this->assertCount(2, $transitions);
-        $this->assertSame('t3', $transitions['t3']->getName());
-        $this->assertSame('t4', $transitions['t4']->getName());
+        $this->assertSame('t3', $transitions[0]->getName());
+        $this->assertSame('t4', $transitions[1]->getName());
 
         $subject->marking = array('c' => true, 'e' => true);
         $transitions = $workflow->getEnabledTransitions($subject);
         $this->assertCount(1, $transitions);
-        $this->assertSame('t5', $transitions['t5']->getName());
+        $this->assertSame('t5', $transitions[0]->getName());
     }
 
-    private function createComplexWorkflow()
+    protected function createComplexWorkflow()
     {
         $definition = new Definition();
 

src/Symfony/Component/Workflow/Validator/DefinitionValidatorInterface.php

@@ -0,0 +1,31 @@
+<?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\Validator;
+
+use Symfony\Component\Workflow\Definition;
+use Symfony\Component\Workflow\Exception\InvalidDefinitionException;
+
+/**
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+interface DefinitionValidatorInterface
+{
+    /**
+     * @param Definition $definition
+     * @param string     $name
+     *
+     * @return bool
+     *
+     * @throws InvalidDefinitionException on invalid definition
+     */
+    public function validate(Definition $definition, $name);
+}

src/Symfony/Component/Workflow/Validator/SinglePlaceWorkflowValidator.php

@@ -0,0 +1,41 @@
+<?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\Validator;
+
+use Symfony\Component\Workflow\Definition;
+use Symfony\Component\Workflow\Exception\InvalidDefinitionException;
+
+/**
+ * If the marking can contain only one place, we should control the definition.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class SinglePlaceWorkflowValidator extends WorkflowValidator
+{
+    public function validate(Definition $definition, $name)
+    {
+        foreach ($definition->getTransitions() as $transition) {
+            if (1 < count($transition->getTos())) {
+                throw new InvalidDefinitionException(
+                    sprintf(
+                        'The marking store of workflow "%s" can not store many places. But the transition "%s" has too many output (%d). Only one is accepted.',
+                        $name,
+                        $transition->getName(),
+                        count($transition->getTos())
+                    )
+                );
+            }
+        }
+
+        return parent::validate($definition, $name);
+    }
+}

src/Symfony/Component/Workflow/Validator/StateMachineValidator.php

@@ -0,0 +1,68 @@
+<?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\Validator;
+
+use Symfony\Component\Workflow\Definition;
+use Symfony\Component\Workflow\Exception\InvalidDefinitionException;
+
+/**
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class StateMachineValidator implements DefinitionValidatorInterface
+{
+    public function validate(Definition $definition, $name)
+    {
+        $transitionFromNames = array();
+        foreach ($definition->getTransitions() as $transition) {
+            // Make sure that each transition has exactly one TO
+            if (1 !== count($transition->getTos())) {
+                throw new InvalidDefinitionException(
+                    sprintf(
+                        'A transition in StateMachine can only have one output. But the transition "%s" in StateMachine "%s" has %d outputs.',
+                        $transition->getName(),
+                        $name,
+                        count($transition->getTos())
+                    )
+                );
+            }
+
+            // Make sure that each transition has exactly one FROM
+            $froms = $transition->getFroms();
+            if (1 !== count($froms)) {
+                throw new InvalidDefinitionException(
+                    sprintf(
+                        'A transition in StateMachine can only have one input. But the transition "%s" in StateMachine "%s" has %d inputs.',
+                        $transition->getName(),
+                        $name,
+                        count($transition->getTos())
+                    )
+                );
+            }
+
+            // Enforcing uniqueness of the names of transitions starting at each node
+            $from = reset($froms);
+            if (isset($transitionFromNames[$from][$transition->getName()])) {
+                throw new InvalidDefinitionException(
+                    sprintf(
+                        'A transition from a place/state must have an unique name. Multiple transitions named "%s" from place/state "%s" where found on StateMachine "%s". ',
+                        $transition->getName(),
+                        $from,
+                        $name
+                    )
+                );
+            }
+            $transitionFromNames[$from][$transition->getName()] = true;
+        }
+
+        return true;
+    }
+}

src/Symfony/Component/Workflow/Validator/WorkflowValidator.php

@@ -0,0 +1,24 @@
+<?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\Validator;
+
+use Symfony\Component\Workflow\Definition;
+
+/**
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class WorkflowValidator implements DefinitionValidatorInterface
+{
+    public function validate(Definition $definition, $name)
+    {
+    }
+}

src/Symfony/Component/Workflow/Workflow.php

@@ -16,11 +16,12 @@ use Symfony\Component\Workflow\Event\Event;
 use Symfony\Component\Workflow\Event\GuardEvent;
 use Symfony\Component\Workflow\Exception\LogicException;
 use Symfony\Component\Workflow\MarkingStore\MarkingStoreInterface;
-use Symfony\Component\Workflow\MarkingStore\UniqueTransitionOutputInterface;
+use Symfony\Component\Workflow\MarkingStore\PropertyAccessorMarkingStore;
 
 /**
  * @author Fabien Potencier <fabien@symfony.com>
  * @author Grégoire Pineau <lyrixx@lyrixx.info>
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 class Workflow
 {
@@ -29,21 +30,12 @@ class Workflow
     private $dispatcher;
     private $name;
 
-    public function __construct(Definition $definition, MarkingStoreInterface $markingStore, EventDispatcherInterface $dispatcher = null, $name = 'unnamed')
+    public function __construct(Definition $definition, MarkingStoreInterface $markingStore = null, EventDispatcherInterface $dispatcher = null, $name = 'unnamed')
     {
         $this->definition = $definition;
-        $this->markingStore = $markingStore;
+        $this->markingStore = $markingStore ?: new PropertyAccessorMarkingStore();
         $this->dispatcher = $dispatcher;
         $this->name = $name;
-
-        // If the marking can contain only one place, we should control the definition
-        if ($markingStore instanceof UniqueTransitionOutputInterface) {
-            foreach ($definition->getTransitions() as $transition) {
-                if (1 < count($transition->getTos())) {
-                    throw new LogicException(sprintf('The marking store (%s) of workflow "%s" can not store many places. But the transition "%s" has too many output (%d). Only one is accepted.', get_class($markingStore), $this->name, $transition->getName(), count($transition->getTos())));
-                }
-            }
-        }
     }
 
     /**
@@ -102,16 +94,10 @@ class Workflow
      */
     public function can($subject, $transitionName)
     {
-        $transitions = $this->definition->getTransitions();
-
-        if (!isset($transitions[$transitionName])) {
-            throw new LogicException(sprintf('Transition "%s" does not exist for workflow "%s".', $transitionName, $this->name));
-        }
-
-        $transition = $transitions[$transitionName];
+        $transitions = $this->getTransitions($transitionName);
         $marking = $this->getMarking($subject);
 
-        return $this->doCan($subject, $marking, $transition);
+        return null !== $this->getTransitionForSubject($subject, $marking, $transitions);
     }
 
     /**
@@ -127,15 +113,13 @@ class Workflow
      */
     public function apply($subject, $transitionName)
     {
-        if (!$this->can($subject, $transitionName)) {
+        $transitions = $this->getTransitions($transitionName);
+        $marking = $this->getMarking($subject);
+
+        if (null === $transition = $this->getTransitionForSubject($subject, $marking, $transitions)) {
             throw new LogicException(sprintf('Unable to apply transition "%s" for workflow "%s".', $transitionName, $this->name));
         }
 
-        // We can shortcut the getMarking method in order to boost performance,
-        // since the "can" method already checks the Marking state
-        $marking = $this->markingStore->getMarking($subject);
-        $transition = $this->definition->getTransitions()[$transitionName];
-
         $this->leave($subject, $transition, $marking);
 
         $this->transition($subject, $transition, $marking);
@@ -162,8 +146,8 @@ class Workflow
         $marking = $this->getMarking($subject);
 
         foreach ($this->definition->getTransitions() as $transition) {
-            if ($this->doCan($subject, $marking, $transition)) {
-                $enabled[$transition->getName()] = $transition;
+            if (null !== $this->getTransitionForSubject($subject, $marking, array($transition))) {
+                $enabled[] = $transition;
             }
         }
 
@@ -175,21 +159,13 @@ class Workflow
         return $this->name;
     }
 
-    private function doCan($subject, Marking $marking, Transition $transition)
-    {
-        foreach ($transition->getFroms() as $place) {
-            if (!$marking->has($place)) {
-                return false;
-            }
-        }
-
-        if (true === $this->guardTransition($subject, $marking, $transition)) {
-            return false;
-        }
-
-        return true;
-    }
-
+    /**
+     * @param object     $subject
+     * @param Marking    $marking
+     * @param Transition $transition
+     *
+     * @return bool|void boolean true if this transition is guarded, ie you cannot use it
+     */
     private function guardTransition($subject, Marking $marking, Transition $transition)
     {
         if (null === $this->dispatcher) {
@@ -263,9 +239,55 @@ class Workflow
         $event = new Event($subject, $marking, $initialTransition);
 
         foreach ($this->definition->getTransitions() as $transition) {
-            if ($this->doCan($subject, $marking, $transition)) {
+            if (null !== $this->getTransitionForSubject($subject, $marking, array($transition))) {
                 $this->dispatcher->dispatch(sprintf('workflow.%s.announce.%s', $this->name, $transition->getName()), $event);
             }
         }
     }
+
+    /**
+     * @param $transitionName
+     *
+     * @return Transition[]
+     */
+    private function getTransitions($transitionName)
+    {
+        $transitions = $this->definition->getTransitions();
+
+        $transitions = array_filter($transitions, function (Transition $transition) use ($transitionName) {
+            return $transitionName === $transition->getName();
+        });
+
+        if (!$transitions) {
+            throw new LogicException(sprintf('Transition "%s" does not exist for workflow "%s".', $transitionName, $this->name));
+        }
+
+        return $transitions;
+    }
+
+    /**
+     * Return the first Transition in $transitions that is valid for the
+     * $subject and $marking. null is returned when you cannot do any Transition
+     * in $transitions on the $subject.
+     *
+     * @param object       $subject
+     * @param Marking      $marking
+     * @param Transition[] $transitions
+     *
+     * @return Transition|null
+     */
+    private function getTransitionForSubject($subject, Marking $marking, array $transitions)
+    {
+        foreach ($transitions as $transition) {
+            foreach ($transition->getFroms() as $place) {
+                if (!$marking->has($place)) {
+                    continue 2;
+                }
+            }
+
+            if (true !== $this->guardTransition($subject, $marking, $transition)) {
+                return $transition;
+            }
+        }
+    }
 }