Calling cancel() on coroutine should cancel pending promise

Author: clue

src/functions.php

@@ -224,10 +224,16 @@ function coroutine(callable $function, ...$args): PromiseInterface
         return resolve($generator);
     }
 
-    $deferred = new Deferred();
+    $promise = null;
+    $deferred = new Deferred(function () use (&$promise) {
+        if ($promise instanceof CancellablePromiseInterface) {
+            $promise->cancel();
+        }
+        $promise = null;
+    });
 
     /** @var callable $next */
-    $next = function () use ($deferred, $generator, &$next) {
+    $next = function () use ($deferred, $generator, &$next, &$promise) {
         try {
             if (!$generator->valid()) {
                 $deferred->resolve($generator->getReturn());

tests/CoroutineTest.php

@@ -2,6 +2,7 @@
 
 namespace React\Tests\Async;
 
+use React\Promise\Promise;
 use function React\Async\coroutine;
 use function React\Promise\reject;
 use function React\Promise\resolve;
@@ -104,4 +105,17 @@ public function testCoroutineReturnsRejectedPromiseIfFunctionYieldsInvalidValue(
 
         $promise->then(null, $this->expectCallableOnceWith(new \UnexpectedValueException('Expected coroutine to yield React\Promise\PromiseInterface, but got integer')));
     }
+
+    public function testCoroutineWillCancelPendingPromiseWhenCallingCancelOnResultingPromise()
+    {
+        $promise = coroutine(function () {
+            yield new Promise(function () { }, function () {
+                throw new \RuntimeException('Operation cancelled', 42);
+            });
+        });
+
+        $promise->cancel();
+
+        $promise->then(null, $this->expectCallableOnceWith(new \RuntimeException('Operation cancelled', 42)));
+    }
 }