Add not_in_list rule

system/Language/en/Validation.php

@@ -48,6 +48,7 @@
    'max_length'            => 'The {field} field cannot exceed {param} characters in length.',
    'min_length'            => 'The {field} field must be at least {param} characters in length.',
    'not_equals'            => 'The {field} field cannot be: {param}.',
+   'not_in_list'           => 'The {field} field must not be one of: {param}.',
    'numeric'               => 'The {field} field must contain only numbers.',
    'regex_match'           => 'The {field} field is not in the correct format.',
    'required'              => 'The {field} field is required.',

system/Validation/Rules.php

@@ -174,8 +174,7 @@ public function is_not_unique(string $str = null, string $field, array $data): b
 			}
 		}
 
-		return (bool) ($row->get()
-						->getRow() !== null);
+		return (bool) ($row->get()->getRow() !== null);
 	}
 
 	//--------------------------------------------------------------------
@@ -190,10 +189,7 @@ public function is_not_unique(string $str = null, string $field, array $data): b
 	 */
 	public function in_list(string $value = null, string $list): bool
 	{
-		$list = explode(',', $list);
-		$list = array_map(function ($value) {
-			return trim($value);
-		}, $list);
+		$list = array_map('trim', explode(',', $list));
 		return in_array($value, $list, true);
 	}
 
@@ -237,8 +233,7 @@ public function is_unique(string $str = null, string $field, array $data): bool
 			}
 		}
 
-		return (bool) ($row->get()
-						->getRow() === null);
+		return (bool) ($row->get()->getRow() === null);
 	}
 
 	//--------------------------------------------------------------------
@@ -334,6 +329,21 @@ public function not_equals(string $str = null, string $val): bool
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * Value should not be within an array of values.
+	 *
+	 * @param string $value
+	 * @param string $list
+	 *
+	 * @return boolean
+	 */
+	public function not_in_list(string $value = null, string $list): bool
+	{
+		return ! $this->in_list($value, $list);
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * Required
 	 *

tests/system/Validation/RulesTest.php

@@ -1319,8 +1319,9 @@ public function lessThanEqualProvider()
 	/**
 	 * @dataProvider inListProvider
 	 *
-	 * @param $str
-	 * @param $expected
+	 * @param string  $first
+	 * @param string  $second
+	 * @param boolean $expected
 	 */
 	public function testInList($first, $second, $expected)
 	{
@@ -1337,6 +1338,30 @@ public function testInList($first, $second, $expected)
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * @dataProvider inListProvider
+	 *
+	 * @param string  $first
+	 * @param string  $second
+	 * @param boolean $expected
+	 */
+	public function testNotInList($first, $second, $expected)
+	{
+		$expected = ! $expected;
+
+		$data = [
+			'foo' => $first,
+		];
+
+		$this->validation->setRules([
+			'foo' => "not_in_list[{$second}]",
+		]);
+
+		$this->assertEquals($expected, $this->validation->run($data));
+	}
+
+	//--------------------------------------------------------------------
+
 	public function inListProvider()
 	{
 		return [

user_guide_src/source/libraries/validation.rst

@@ -781,6 +781,7 @@ less_than_equal_to      Yes         Fails if field is greater than the parameter
 matches                 Yes         The value must match the value of the field in the parameter.                                   matches[field]
 max_length              Yes         Fails if field is longer than the parameter value.                                              max_length[8]
 min_length              Yes         Fails if field is shorter than the parameter value.                                             min_length[3]
+not_in_list             Yes         Fails if field is within a predetermined list.                                                  not_in_list[red,blue,green]
 numeric                 No          Fails if field contains anything other than numeric characters.
 regex_match             Yes         Fails if field does not match the regular expression.                                           regex_match[/regex/]
 permit_empty            No          Allows the field to receive an empty array, empty string, null or false.
@@ -829,7 +830,7 @@ Rule                    Parameter   Description
 ======================= =========== =============================================================================================== ========================================
 uploaded                Yes         Fails if the name of the parameter does not match the name of any uploaded files.               uploaded[field_name]
 max_size                Yes         Fails if the uploaded file named in the parameter is larger than the second parameter in        max_size[field_name,2048]
-                                    kilobytes (kb). Or if the file is larger than allowed maximum size declared in 
+                                    kilobytes (kb). Or if the file is larger than allowed maximum size declared in
                                     php.ini config file - ``upload_max_filesize`` directive.
 max_dims                Yes         Fails if the maximum width and height of an uploaded image exceed values. The first parameter   max_dims[field_name,300,150]
                                     is the field name. The second is the width, and the third is the height. Will also fail if