psr-7 attempt to set the Host header during construction

src/RequestTrait.php

@@ -69,6 +69,13 @@ private function initialize($uri = null, $method = null, $body = 'php://memory',
         list($this->headerNames, $headers) = $this->filterHeaders($headers);
         $this->assertHeaders($headers);
         $this->headers = $headers;
+
+        // per PSR-7: attempt to set the Host header from a provided URI if no
+        // Host header is provided
+        if (! $this->hasHeader('Host') && $this->uri->getHost()) {
+            $this->headerNames['host'] = 'Host';
+            $this->headers['Host'] = [$this->getHostFromUri()];
+        }
     }
 
     /**

test/RequestTest.php

@@ -395,6 +395,19 @@ public function testGetHostHeaderLineReturnsEmptyStringIfUriDoesNotContainHost()
         $this->assertEmpty($request->getHeaderLine('host'));
     }
 
+    public function testHostHeaderSetFromUriOnCreationIfNoHostHeaderSpecified()
+    {
+        $request = new Request('http://www.example.com');
+        $this->assertTrue($request->hasHeader('Host'));
+        $this->assertEquals('www.example.com', $request->getHeaderLine('host'));
+    }
+
+    public function testHostHeaderNotSetFromUriOnCreationIfHostHeaderSpecified()
+    {
+        $request = new Request('http://www.example.com', null, 'php://memory', ['Host' => 'www.test.com']);
+        $this->assertEquals('www.test.com', $request->getHeaderLine('host'));
+    }
+
     public function testPassingPreserveHostFlagWhenUpdatingUriDoesNotUpdateHostHeader()
     {
         $request = (new Request())