minor #23781 [Workflow] do not emit not needed guard events (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
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[Workflow] do not emit not needed guard events

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #23677
| License       | MIT
| Doc PR        |

Commits
-------

47c68e1 [Workflow] do not emit not needed guard events

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

@@ -137,6 +137,31 @@ public function testCanWithGuard()
         $this->assertFalse($workflow->can($subject, 't1'));
     }
 
+    public function testCanDoesNotTriggerGuardEventsForNotEnabledTransitions()
+    {
+        $definition = $this->createComplexWorkflowDefinition();
+        $subject = new \stdClass();
+        $subject->marking = null;
+
+        $dispatchedEvents = array();
+        $eventDispatcher = new EventDispatcher();
+
+        $workflow = new Workflow($definition, new MultipleStateMarkingStore(), $eventDispatcher, 'workflow_name');
+        $workflow->apply($subject, 't1');
+        $workflow->apply($subject, 't2');
+
+        $eventDispatcher->addListener('workflow.workflow_name.guard.t3', function () use (&$dispatchedEvents) {
+            $dispatchedEvents[] = 'workflow_name.guard.t3';
+        });
+        $eventDispatcher->addListener('workflow.workflow_name.guard.t4', function () use (&$dispatchedEvents) {
+            $dispatchedEvents[] = 'workflow_name.guard.t4';
+        });
+
+        $workflow->can($subject, 't3');
+
+        $this->assertSame(array('workflow_name.guard.t3'), $dispatchedEvents);
+    }
+
     /**
      * @expectedException \Symfony\Component\Workflow\Exception\LogicException
      * @expectedExceptionMessage Unable to apply transition "t2" for workflow "unnamed".

src/Symfony/Component/Workflow/Workflow.php

@@ -92,10 +92,19 @@ public function getMarking($subject)
      */
     public function can($subject, $transitionName)
     {
-        $transitions = $this->getEnabledTransitions($subject);
+        $transitions = $this->definition->getTransitions();
+        $marking = $this->getMarking($subject);
 
         foreach ($transitions as $transition) {
-            if ($transitionName === $transition->getName()) {
+            foreach ($transition->getFroms() as $place) {
+                if (!$marking->has($place)) {
+                    // do not emit guard events for transitions where the marking does not contain
+                    // all "from places" (thus the transition couldn't be applied anyway)
+                    continue 2;
+                }
+            }
+
+            if ($transitionName === $transition->getName() && $this->doCan($subject, $marking, $transition)) {
                 return true;
             }
         }