Load hosts file by default

Author: clue

README.md

@@ -40,6 +40,11 @@ $loop->run();
 
 See also the [first example](examples).
 
+> Note that the factory loads the hosts file from the filesystem once when
+  creating the resolver instance.
+  Ideally, this method should thus be executed only once before the loop starts
+  and not repeatedly while it is running.
+
 Pending DNS queries can be cancelled by cancelling its pending promise like so:
 
 ```php

src/Resolver/Factory.php

@@ -4,21 +4,24 @@
 
 use React\Cache\ArrayCache;
 use React\Cache\CacheInterface;
-use React\Dns\Query\Executor;
-use React\Dns\Query\CachedExecutor;
-use React\Dns\Query\RecordCache;
+use React\Dns\Config\HostsFile;
 use React\Dns\Protocol\Parser;
 use React\Dns\Protocol\BinaryDumper;
-use React\EventLoop\LoopInterface;
+use React\Dns\Query\CachedExecutor;
+use React\Dns\Query\Executor;
+use React\Dns\Query\ExecutorInterface;
+use React\Dns\Query\HostsFileExecutor;
+use React\Dns\Query\RecordCache;
 use React\Dns\Query\RetryExecutor;
 use React\Dns\Query\TimeoutExecutor;
+use React\EventLoop\LoopInterface;
 
 class Factory
 {
     public function create($nameserver, LoopInterface $loop)
     {
         $nameserver = $this->addPortToServerIfMissing($nameserver);
-        $executor = $this->createRetryExecutor($loop);
+        $executor = $this->decorateHostsFileExecutor($this->createRetryExecutor($loop));
 
         return new Resolver($nameserver, $executor);
     }
@@ -30,11 +33,30 @@ public function createCached($nameserver, LoopInterface $loop, CacheInterface $c
         }
 
         $nameserver = $this->addPortToServerIfMissing($nameserver);
-        $executor = $this->createCachedExecutor($loop, $cache);
+        $executor = $this->decorateHostsFileExecutor($this->createCachedExecutor($loop, $cache));
 
         return new Resolver($nameserver, $executor);
     }
 
+    /**
+     * Tries to load the hosts file and decorates the given executor on success
+     *
+     * @param ExecutorInterface $executor
+     * @return ExecutorInterface
+     * @codeCoverageIgnore
+     */
+    private function decorateHostsFileExecutor(ExecutorInterface $executor)
+    {
+        try {
+            $hosts = HostsFile::loadFromPathBlocking();
+        } catch (\RuntimeException $e) {
+            // ignore this file if it can not be loaded
+            return $executor;
+        }
+
+        return new HostsFileExecutor($hosts, $executor);
+    }
+
     protected function createExecutor(LoopInterface $loop)
     {
         return new TimeoutExecutor(

tests/FunctionalResolverTest.php

@@ -17,6 +17,18 @@ public function setUp()
         $this->resolver = $factory->create('8.8.8.8', $this->loop);
     }
 
+    public function testResolveLocalhostResolves()
+    {
+        if (DIRECTORY_SEPARATOR === '\\') {
+            $this->markTestSkipped('Not supported on Windows');
+        }
+
+        $promise = $this->resolver->resolve('localhost');
+        $promise->then($this->expectCallableOnce(), $this->expectCallableNever());
+
+        $this->loop->run();
+    }
+
     public function testResolveGoogleResolves()
     {
         $promise = $this->resolver->resolve('google.com');

tests/Resolver/FactoryTest.php

@@ -4,6 +4,7 @@
 
 use React\Dns\Resolver\Factory;
 use React\Tests\Dns\TestCase;
+use React\Dns\Query\HostsFileExecutor;
 
 class FactoryTest extends TestCase
 {
@@ -39,7 +40,7 @@ public function createCachedShouldCreateResolverWithCachedExecutor()
         $resolver = $factory->createCached('8.8.8.8:53', $loop);
 
         $this->assertInstanceOf('React\Dns\Resolver\Resolver', $resolver);
-        $executor = $this->getResolverPrivateMemberValue($resolver, 'executor');
+        $executor = $this->getResolverPrivateExecutor($resolver);
         $this->assertInstanceOf('React\Dns\Query\CachedExecutor', $executor);
         $recordCache = $this->getCachedExecutorPrivateMemberValue($executor, 'cache');
         $recordCacheCache = $this->getRecordCachePrivateMemberValue($recordCache, 'cache');
@@ -57,7 +58,7 @@ public function createCachedShouldCreateResolverWithCachedExecutorWithCustomCach
         $resolver = $factory->createCached('8.8.8.8:53', $loop, $cache);
 
         $this->assertInstanceOf('React\Dns\Resolver\Resolver', $resolver);
-        $executor = $this->getResolverPrivateMemberValue($resolver, 'executor');
+        $executor = $this->getResolverPrivateExecutor($resolver);
         $this->assertInstanceOf('React\Dns\Query\CachedExecutor', $executor);
         $recordCache = $this->getCachedExecutorPrivateMemberValue($executor, 'cache');
         $recordCacheCache = $this->getRecordCachePrivateMemberValue($recordCache, 'cache');
@@ -92,6 +93,20 @@ public static function factoryShouldAddDefaultPortProvider()
         );
     }
 
+    private function getResolverPrivateExecutor($resolver)
+    {
+        $executor = $this->getResolverPrivateMemberValue($resolver, 'executor');
+
+        if ($executor instanceof HostsFileExecutor) {
+            $reflector = new \ReflectionProperty('React\Dns\Query\HostsFileExecutor', 'fallback');
+            $reflector->setAccessible(true);
+
+            $executor = $reflector->getValue($executor);
+        }
+
+        return $executor;
+    }
+
     private function getResolverPrivateMemberValue($resolver, $field)
     {
         $reflector = new \ReflectionProperty('React\Dns\Resolver\Resolver', $field);