Improve DNS error messages

Author: clue

src/DnsConnector.php

@@ -41,7 +41,7 @@ public function connect($uri)
         }
 
         return $this
-            ->resolveHostname($host)
+            ->resolveHostname($host, $uri)
             ->then(function ($ip) use ($connector, $host, $parts) {
                 $uri = '';
 
@@ -89,18 +89,20 @@ public function connect($uri)
             });
     }
 
-    private function resolveHostname($host)
+    private function resolveHostname($host, $uri)
     {
         $promise = $this->resolver->resolve($host);
 
         return new Promise\Promise(
-            function ($resolve, $reject) use ($promise) {
+            function ($resolve, $reject) use ($promise, $uri) {
                 // resolve/reject with result of DNS lookup
-                $promise->then($resolve, $reject);
+                $promise->then($resolve, function ($e) use ($uri, $reject) {
+                    $reject(new RuntimeException('Connection to ' . $uri .' failed during DNS lookup: ' . $e->getMessage(), 0, $e));
+                });
             },
-            function ($_, $reject) use ($promise) {
+            function ($_, $reject) use ($promise, $uri) {
                 // cancellation should reject connection attempt
-                $reject(new RuntimeException('Connection attempt cancelled during DNS lookup'));
+                $reject(new RuntimeException('Connection to ' . $uri . ' cancelled during DNS lookup'));
 
                 // (try to) cancel pending DNS lookup
                 if ($promise instanceof CancellablePromiseInterface) {

tests/DnsConnectorTest.php

@@ -77,14 +77,38 @@ public function testRejectsImmediatelyIfUriIsInvalid()
         $promise->then($this->expectCallableNever(), $this->expectCallableOnce());
     }
 
+    /**
+     * @expectedException RuntimeException
+     * @expectedExceptionMessage Connection to example.invalid:80 failed during DNS lookup: DNS error
+     */
     public function testSkipConnectionIfDnsFails()
     {
-        $this->resolver->expects($this->once())->method('resolve')->with($this->equalTo('example.invalid'))->will($this->returnValue(Promise\reject()));
+        $promise = Promise\reject(new \RuntimeException('DNS error'));
+        $this->resolver->expects($this->once())->method('resolve')->with($this->equalTo('example.invalid'))->willReturn($promise);
         $this->tcp->expects($this->never())->method('connect');
 
-        $this->connector->connect('example.invalid:80');
+        $promise = $this->connector->connect('example.invalid:80');
+
+        $this->throwRejection($promise);
+    }
+
+    public function testRejectionExceptionUsesPreviousExceptionIfDnsFails()
+    {
+        $exception = new \RuntimeException();
+
+        $this->resolver->expects($this->once())->method('resolve')->with($this->equalTo('example.invalid'))->willReturn(Promise\reject($exception));
+
+        $promise = $this->connector->connect('example.invalid:80');
+
+        $promise->then(null, function ($e) {
+            throw $e->getPrevious();
+        })->then(null, $this->expectCallableOnceWith($this->identicalTo($exception)));
     }
 
+    /**
+     * @expectedException RuntimeException
+     * @expectedExceptionMessage Connection to example.com:80 cancelled during DNS lookup
+     */
     public function testCancelDuringDnsCancelsDnsAndDoesNotStartTcpConnection()
     {
         $pending = new Promise\Promise(function () { }, $this->expectCallableOnce());
@@ -94,7 +118,7 @@ public function testCancelDuringDnsCancelsDnsAndDoesNotStartTcpConnection()
         $promise = $this->connector->connect('example.com:80');
         $promise->cancel();
 
-        $promise->then($this->expectCallableNever(), $this->expectCallableOnce());
+        $this->throwRejection($promise);
     }
 
     public function testCancelDuringTcpConnectionCancelsTcpConnection()
@@ -108,4 +132,14 @@ public function testCancelDuringTcpConnectionCancelsTcpConnection()
 
         $promise->then($this->expectCallableNever(), $this->expectCallableOnce());
     }
+
+    private function throwRejection($promise)
+    {
+        $ex = null;
+        $promise->then(null, function ($e) use (&$ex) {
+            $ex = $e;
+        });
+
+        throw $ex;
+    }
 }