Fix non-conforming URL validation

Json schema spec says URLs are validated as per RFC-3986, but PHP's
FILTER_VALIDATE_URL can't cope with relative path references, which are
explicitly allowed. See https://tools.ietf.org/html/rfc3986#section-4.2
for further information.

Author: erayd

src/JsonSchema/Constraints/FormatConstraint.php

@@ -81,7 +81,26 @@ public function check(&$element, $schema = null, JsonPointer $path = null, $i =
 
             case 'uri':
                 if (null === filter_var($element, FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE)) {
-                    $this->addError($path, 'Invalid URL format', 'format', array('format' => $schema->format));
+                    // FILTER_VALIDATE_URL does not conform to RFC-3986, and cannot handle relative URLs, but
+                    // the json-schema spec uses RFC-3986, so need a bit of hackery to properly validate them.
+                    // See https://tools.ietf.org/html/rfc3986#section-4.2 for additional information.
+                    if (substr($element, 0, 2) === '//') { // network-path reference
+                        $validURL = filter_var('scheme:' . $element, FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE);
+                    } elseif (substr($element, 0, 1) === '/') { // absolute-path reference
+                        $validURL = filter_var('scheme://host' . $element, FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE);
+                    } elseif (strlen($element)) { // relative-path reference
+                        $pathParts = explode('/', $element, 2)[0];
+                        if ($pathParts[0] !== '.' && strpos($pathParts, ':') !== false) {
+                            $validURL = null;
+                        } else {
+                            $validURL = filter_var('scheme://host/' . $element, FILTER_VALIDATE_URL, FILTER_NULL_ON_FAILURE);
+                        }
+                    } else {
+                        $validURL = null;
+                    }
+                    if ($validURL === null) {
+                        $this->addError($path, 'Invalid URL format', 'format', array('format' => $schema->format));
+                    }
                 }
                 break;
 

tests/Constraints/FormatTest.php

@@ -126,6 +126,9 @@ public function getValidFormats()
             array('555 320 1212', 'phone'),
 
             array('http://bluebox.org', 'uri'),
+            array('//bluebox.org', 'uri'),
+            array('/absolutePathReference/', 'uri'),
+            array('relativePathReference/', 'uri'),
 
             array('[email protected]', 'email'),
 
@@ -175,6 +178,7 @@ public function getInvalidFormats()
             array('1 123 4424', 'phone'),
 
             array('htt:/bluebox.org', 'uri'),
+            array('', 'uri'),
 
             array('info@somewhere', 'email'),