Improve FilterVar with FILTER_VALIDATE_* options

The `filter_var` function is more of a sanitizer, but we as
a validation library do not care for that use case.

We should treat its sanitizings as a signal for checking if
the type after sanitization matches the option provided.

This fixes #1387

docs/rules/FilterVar.md

@@ -22,6 +22,7 @@ v::filterVar(FILTER_VALIDATE_DOMAIN, FILTER_FLAG_HOSTNAME)->validate('@local');
 
 Version  | Description
 ---------|-------------
+  2.3.0  | `v::filterVar(FILTER_VALIDATE_INT)->validate(0)` is no longer false
   2.0.15 | Allow validating domains
    0.8.0 | Created
 

library/Rules/FilterVar.php

@@ -15,7 +15,8 @@ namespace Respect\Validation\Rules;
 
 use Respect\Validation\Exceptions\ComponentException;
 
-use function in_array;
+use function array_key_exists;
+use function filter_var;
 use function is_array;
 use function is_int;
 
@@ -36,14 +37,14 @@ use const FILTER_VALIDATE_URL;
 final class FilterVar extends AbstractEnvelope
 {
     private const ALLOWED_FILTERS = [
-        FILTER_VALIDATE_BOOLEAN,
-        FILTER_VALIDATE_DOMAIN,
-        FILTER_VALIDATE_EMAIL,
-        FILTER_VALIDATE_FLOAT,
-        FILTER_VALIDATE_INT,
-        FILTER_VALIDATE_IP,
-        FILTER_VALIDATE_REGEXP,
-        FILTER_VALIDATE_URL,
+        FILTER_VALIDATE_BOOLEAN => 'is_bool',
+        FILTER_VALIDATE_DOMAIN => 'is_string',
+        FILTER_VALIDATE_EMAIL => 'is_string',
+        FILTER_VALIDATE_FLOAT => 'is_float',
+        FILTER_VALIDATE_INT => 'is_int',
+        FILTER_VALIDATE_IP => 'is_string',
+        FILTER_VALIDATE_REGEXP => 'is_string',
+        FILTER_VALIDATE_URL => 'is_string',
     ];
 
     /**
@@ -55,7 +56,7 @@ final class FilterVar extends AbstractEnvelope
      */
     public function __construct(int $filter, $options = null)
     {
-        if (!in_array($filter, self::ALLOWED_FILTERS)) {
+        if (!array_key_exists($filter, self::ALLOWED_FILTERS)) {
             throw new ComponentException('Cannot accept the given filter');
         }
 
@@ -64,6 +65,10 @@ final class FilterVar extends AbstractEnvelope
             $arguments[] = $options;
         }
 
-        parent::__construct(new Callback('filter_var', ...$arguments));
+        parent::__construct(new Callback(static function ($input) use ($filter, $arguments) {
+            return (self::ALLOWED_FILTERS[$filter])(
+                filter_var($input, ...$arguments)
+            );
+        }));
     }
 }

tests/unit/Rules/FilterVarTest.php

@@ -60,6 +60,7 @@ final class FilterVarTest extends RuleTestCase
             [new FilterVar(FILTER_VALIDATE_BOOLEAN), 'On'],
             [new FilterVar(FILTER_VALIDATE_URL, FILTER_FLAG_QUERY_REQUIRED), 'http://example.com?foo=bar'],
             [new FilterVar(FILTER_VALIDATE_DOMAIN), 'example.com'],
+            [new FilterVar(FILTER_VALIDATE_INT), '0'],
         ];
     }