Merge pull request #47 from clue-labs/double-cancellation

Cancellation handler must only be called once, ignore double cancellation

Author: jsor

src/Promise.php

@@ -91,7 +91,10 @@ public function cancel()
             return;
         }
 
-        $this->call($this->canceller);
+        $canceller = $this->canceller;
+        $this->canceller = null;
+
+        $this->call($canceller);
     }
 
     private function resolver(callable $onFulfilled = null, callable $onRejected = null, callable $onProgress = null)

tests/PromiseTest/CancelTestTrait.php

@@ -189,6 +189,31 @@ public function cancelShouldTriggerCancellerWhenAllChildrenCancel()
         $child2->cancel();
     }
 
+    /** @test */
+    public function cancelShouldNotTriggerCancellerWhenCancellingOneChildrenMultipleTimes()
+    {
+        $adapter = $this->getPromiseTestAdapter($this->expectCallableNever());
+
+        $child1 = $adapter->promise()
+            ->then()
+            ->then();
+
+        $child2 = $adapter->promise()
+            ->then();
+
+        $child1->cancel();
+        $child1->cancel();
+    }
+
+    /** @test */
+    public function cancelShouldTriggerCancellerOnlyOnceWhenCancellingMultipleTimes()
+    {
+        $adapter = $this->getPromiseTestAdapter($this->expectCallableOnce());
+
+        $adapter->promise()->cancel();
+        $adapter->promise()->cancel();
+    }
+
     /** @test */
     public function cancelShouldAlwaysTriggerCancellerWhenCalledOnRootPromise()
     {