Support promise cancellation for CachingExecutor

Author: clue

src/Query/CachingExecutor.php

@@ -4,6 +4,7 @@
 
 use React\Cache\CacheInterface;
 use React\Dns\Model\Message;
+use React\Promise\Promise;
 
 class CachingExecutor implements ExecutorInterface
 {
@@ -30,21 +31,29 @@ public function query($nameserver, Query $query)
         $cache = $this->cache;
         $executor = $this->executor;
 
-        return $cache->get($id)->then(function ($message) use ($nameserver, $query, $id, $cache, $executor) {
-            // return cached response message on cache hit
-            if ($message !== null) {
-                return $message;
-            }
-
-            // perform DNS lookup if not already cached
-            return $executor->query($nameserver, $query)->then(
-                function (Message $message) use ($cache, $id) {
-                    // DNS response message received => store in cache and return
-                    $cache->set($id, $message, CachingExecutor::TTL);
-
-                    return $message;
+        $pending = $cache->get($id);
+        return new Promise(function ($resolve, $reject) use ($nameserver, $query, $id, $cache, $executor, &$pending) {
+            $pending->then(
+                function ($message) use ($nameserver, $query, $id, $cache, $executor, &$pending) {
+                    // return cached response message on cache hit
+                    if ($message !== null) {
+                        return $message;
+                    }
+
+                    // perform DNS lookup if not already cached
+                    return $pending = $executor->query($nameserver, $query)->then(
+                        function (Message $message) use ($cache, $id) {
+                            // DNS response message received => store in cache and return
+                            $cache->set($id, $message, CachingExecutor::TTL);
+
+                            return $message;
+                        }
+                    );
                 }
-            );
+            )->then($resolve, $reject);
+        }, function ($_, $reject) use (&$pending, $query) {
+            $reject(new \RuntimeException('DNS query for ' . $query->name . ' has been cancelled'));
+            $pending->cancel();
         });
     }
 }

tests/Query/CachingExecutorTest.php

@@ -101,8 +101,6 @@ public function testQueryWillReturnRejectedPromiseWhenCacheReturnsMissAndFallbac
 
     public function testCancelQueryWillReturnRejectedPromiseAndCancelPendingPromiseFromCache()
     {
-        $this->markTestIncomplete();
-
         $fallback = $this->getMockBuilder('React\Dns\Query\ExecutorInterface')->getMock();
         $fallback->expects($this->never())->method('query');
 
@@ -122,8 +120,6 @@ public function testCancelQueryWillReturnRejectedPromiseAndCancelPendingPromiseF
 
     public function testCancelQueryWillReturnRejectedPromiseAndCancelPendingPromiseFromFallbackExecutorWhenCacheReturnsMiss()
     {
-        $this->markTestIncomplete();
-
         $pending = new Promise(function () { }, $this->expectCallableOnce());
         $fallback = $this->getMockBuilder('React\Dns\Query\ExecutorInterface')->getMock();
         $fallback->expects($this->once())->method('query')->willReturn($pending);