Adding isValidHost method

Improve Host Validation according to RFC3986

- https://tools.ietf.org/html/rfc3986#appendix-A
- https://tools.ietf.org/html/rfc3986#section-3.2.2

A host can be undefined it is up to the URI scheme
to validate if the host presence is required or not

CHANGELOG.md

@@ -6,6 +6,7 @@ All Notable changes to `league-uri-parser` will be documented in this file
 
 ### Added
 
+- `Parser::isValidHost` method
 - `ParserException::createFromInvalidScheme` replaces `ParserException::createFromInvalidState` usage
 - `ParserException::createFromInvalidPath` replaces `ParserException::createFromInvalidState` usage
 

src/HostValidation.php

@@ -37,15 +37,27 @@ trait HostValidation
      */
     protected function filterHost($host)
     {
-        if (filter_var($host, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)
-            || $this->isValidHostnameIpv6($host)
-            || $this->isValidHostname($host)) {
+        if ($this->isValidHost($host)) {
             return $host;
         }
 
         throw ParserException::createFromInvalidHost($host);
     }
 
+    /**
+     * Tell whether a Host is valid
+     *
+     * @param  string $host
+     * @return bool
+     */
+    public function isValidHost($host)
+    {
+        return '' == $host
+            || filter_var($host, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)
+            || $this->isValidHostnameIpv6($host)
+            || $this->isValidHostname($host);
+    }
+
     /**
      * validate an Ipv6 Hostname
      *

test/ParserTest.php

@@ -609,7 +609,6 @@ public function testInvalidURI()
             'invalid host and URI' => ['2620:0:1cfe:face:b00c::3'],
             'invalid scheme and path' => ['0scheme://host/path?query#fragment'],
             'invalid path PHP bug #72811' => ['[::1]:80'],
-            'invalid uri with authority without host' => ['//user@:80'],
         ];
     }
 }