Fix #2143

When trying to load rules from a configuration file, the Form validation library matched against
ruri_string() as opposed to 'controller/method' like described in the manual. Since ruri_string()
also makes sense, now both are being checked with ruri_string() having a higher precedence.

Supersedes PR #2224
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index e8bd25b..852fc71 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -414,17 +414,14 @@
 				return FALSE;
 			}
 
-			// Is there a validation rule for the particular URI being accessed?
-			$uri = ($group === '') ? trim($this->CI->uri->ruri_string(), '/') : $group;
+			if (empty($group))
+			{
+				// Is there a validation rule for the particular URI being accessed?
+				$group = trim($this->CI->uri->ruri_string(), '/');
+				isset($this->_config_rules[$group]) OR $group = $this->CI->router->class.'/'.$this->CI->router->method;
+			}
 
-			if ($uri !== '' && isset($this->_config_rules[$uri]))
-			{
-				$this->set_rules($this->_config_rules[$uri]);
-			}
-			else
-			{
-				$this->set_rules($this->_config_rules);
-			}
+			$this->set_rules(isset($this->_config_rules[$group]) ? $this->_config_rules[$group] : $this->_config_rules);
 
 			// Were we able to set the rules correctly?
 			if (count($this->_field_data) === 0)
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 32d033c..2ad8eff 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -638,6 +638,7 @@
 -  Fixed a bug (#2579) - :doc:`Query Builder <database/query_builder>`s "no escape" functionality didn't work properly with query cache.
 -  Fixed a bug (#2237) - :doc:`Parser Library <libraries/parser>` failed if the same tag pair is used more than once within a template.
 -  Fixed a bug (#2268) - :doc:`Security Library <libraries/security>` didn't properly match JavaScript events.
+-  Fixed a bug (#2143) - :doc:`Form Validation Library <libraries/form_validation>` didn't check for rule groups named in a *controller/method* manner when trying to load from a config file.
 
 Version 2.1.4
 =============