bug #29141 [Workflow] Fixed bug of buildTransitionBlockerList when many transition are enabled (Tetragramat, lyrixx)

This PR was merged into the 4.1 branch.

Discussion
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[Workflow] Fixed bug of buildTransitionBlockerList when many transition are enabled

| Q             | A
| ------------- | ---
| Branch?       | 4.1
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #28429 #28432 #28493
| License       | MIT
| Doc PR        |

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Commits
-------

732f343572 [Workflow] Made code simpler
db69ccc185 method buildTransitionBlockerList returns TransitionBlockerList of expected transition

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

@@ -3,7 +3,10 @@
 namespace Symfony\Component\Workflow\Tests;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+use Symfony\Component\Workflow\Event\GuardEvent;
 use Symfony\Component\Workflow\StateMachine;
+use Symfony\Component\Workflow\TransitionBlocker;
 
 class StateMachineTest extends TestCase
 {
@@ -38,4 +41,70 @@ class StateMachineTest extends TestCase
         $this->assertTrue($net->can($subject, 't2'));
         $this->assertTrue($net->can($subject, 't3'));
     }
+
+    public function testBuildTransitionBlockerList()
+    {
+        $definition = $this->createComplexStateMachineDefinition();
+
+        $net = new StateMachine($definition);
+        $subject = new \stdClass();
+
+        $subject->marking = 'a';
+        $this->assertTrue($net->buildTransitionBlockerList($subject, 't1')->isEmpty());
+        $subject->marking = 'd';
+        $this->assertTrue($net->buildTransitionBlockerList($subject, 't1')->isEmpty());
+
+        $subject->marking = 'b';
+        $this->assertFalse($net->buildTransitionBlockerList($subject, 't1')->isEmpty());
+    }
+
+    public function testBuildTransitionBlockerListWithMultipleTransitions()
+    {
+        $definition = $this->createComplexStateMachineDefinition();
+
+        $net = new StateMachine($definition);
+        $subject = new \stdClass();
+
+        $subject->marking = 'b';
+        $this->assertTrue($net->buildTransitionBlockerList($subject, 't2')->isEmpty());
+        $this->assertTrue($net->buildTransitionBlockerList($subject, 't3')->isEmpty());
+    }
+
+    public function testBuildTransitionBlockerListReturnsExpectedReasonOnBranchMerge()
+    {
+        $definition = $this->createComplexStateMachineDefinition();
+
+        $dispatcher = new EventDispatcher();
+        $net = new StateMachine($definition, null, $dispatcher);
+
+        $dispatcher->addListener('workflow.guard', function (GuardEvent $event) {
+            $event->addTransitionBlocker(new TransitionBlocker(\sprintf('Transition blocker of place %s', $event->getTransition()->getFroms()[0]), 'blocker'));
+        });
+
+        $subject = new \stdClass();
+
+        // There may be multiple transitions with the same name. Make sure that transitions
+        // that are not enabled by the marking are evaluated.
+        // see https://github.com/symfony/symfony/issues/28432
+
+        // Test if when you are in place "a"trying transition "t1" then returned
+        // blocker list contains guard blocker instead blockedByMarking
+        $subject->marking = 'a';
+        $transitionBlockerList = $net->buildTransitionBlockerList($subject, 't1');
+        $this->assertCount(1, $transitionBlockerList);
+        $blockers = iterator_to_array($transitionBlockerList);
+
+        $this->assertSame('Transition blocker of place a', $blockers[0]->getMessage());
+        $this->assertSame('blocker', $blockers[0]->getCode());
+
+        // Test if when you are in place "d" trying transition "t1" then
+        // returned blocker list contains guard blocker instead blockedByMarking
+        $subject->marking = 'd';
+        $transitionBlockerList = $net->buildTransitionBlockerList($subject, 't1');
+        $this->assertCount(1, $transitionBlockerList);
+        $blockers = iterator_to_array($transitionBlockerList);
+
+        $this->assertSame('Transition blocker of place d', $blockers[0]->getMessage());
+        $this->assertSame('blocker', $blockers[0]->getCode());
+    }
 }

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

@@ -195,6 +195,32 @@ class WorkflowTest extends TestCase
         $workflow->buildTransitionBlockerList($subject, '404 Not Found');
     }
 
+    public function testBuildTransitionBlockerList()
+    {
+        $definition = $this->createComplexWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+        $workflow = new Workflow($definition, new MultipleStateMarkingStore());
+
+        $this->assertTrue($workflow->buildTransitionBlockerList($subject, 't1')->isEmpty());
+        $this->assertFalse($workflow->buildTransitionBlockerList($subject, 't2')->isEmpty());
+
+        $subject->marking = array('b' => 1);
+
+        $this->assertFalse($workflow->buildTransitionBlockerList($subject, 't1')->isEmpty());
+        $this->assertFalse($workflow->buildTransitionBlockerList($subject, 't2')->isEmpty());
+
+        $subject->marking = array('b' => 1, 'c' => 1);
+
+        $this->assertFalse($workflow->buildTransitionBlockerList($subject, 't1')->isEmpty());
+        $this->assertTrue($workflow->buildTransitionBlockerList($subject, 't2')->isEmpty());
+
+        $subject->marking = array('f' => 1);
+
+        $this->assertFalse($workflow->buildTransitionBlockerList($subject, 't5')->isEmpty());
+        $this->assertTrue($workflow->buildTransitionBlockerList($subject, 't6')->isEmpty());
+    }
+
     public function testBuildTransitionBlockerListReturnsReasonsProvidedByMarking()
     {
         $definition = $this->createComplexWorkflowDefinition();

src/Symfony/Component/Workflow/TransitionBlockerList.php

@@ -37,6 +37,17 @@ final class TransitionBlockerList implements \IteratorAggregate, \Countable
         $this->blockers[] = $blocker;
     }
 
+    public function has(string $code): bool
+    {
+        foreach ($this->blockers as $blocker) {
+            if ($code === $blocker->getCode()) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     public function clear(): void
     {
         $this->blockers = array();

src/Symfony/Component/Workflow/Workflow.php

@@ -119,7 +119,15 @@ class Workflow implements WorkflowInterface
             $transitionBlockerList = $this->buildTransitionBlockerListForTransition($subject, $marking, $transition);
 
             if ($transitionBlockerList->isEmpty()) {
-                continue;
+                return $transitionBlockerList;
+            }
+
+            // We prefer to return transitions blocker by something else than
+            // marking. Because it means the marking was OK. Transitions are
+            // deterministic: it's not possible to have many transitions enabled
+            // at the same time that match the same marking with the same name
+            if (!$transitionBlockerList->has(TransitionBlocker::BLOCKED_BY_MARKING)) {
+                return $transitionBlockerList;
             }
         }