When NoShipping is used, print rule Name as error message to inform the user.

Special care is taken (using a global array of messages...) to ensure that the message is not printed twice...

language/en-GB/en-GB.plg_vmshipment_rules_shipping.ini

@@ -56,3 +56,5 @@ VMSHIPMENT_RULES_EVALUATE_UNKNOWN_VALUE="Evaluation yields unknown value while e
 
 VMSHIPMENT_RULES_EVALUATE_LISTFUNCTION_ARGS="List function '%s' requires all arguments to be lists. (Full rule: '%s')" 
 VMSHIPMENT_RULES_EVALUATE_LISTFUNCTION_UNKNOWN="Unknown list function '%s' encountered. (Full rule: '%s')" 
+
+VMSHIPMENT_RULES_NOSHIPPING_MESSAGE="%s"

rules_shipping_base.php

@@ -29,6 +29,9 @@ if (class_exists ('plgVmShipmentRules_Shipping_Base')) {
 	return;
 }
 
+// Keep track of warning messages, so we don't print them twice:
+$printed_warnings = array();
+
 /** Shipping costs according to general rules.
  *  Supported Variables: Weight, ZIP, Amount, Products (1 for each product, even if multiple ordered), Articles
  *  Assignable variables: Shipping, Name
@@ -58,6 +61,16 @@ class plgVmShipmentRules_Shipping_Base extends vmPSPlugin {
 	public function getVmPluginCreateTableSQL () {
 		return $this->createTableSQL ('Shipment Rules Table');
 	}
+	
+	public function printWarning($message) {
+		global $printed_warnings;
+// 		JFactory::getApplication()->enqueueMessage("<pre>warnings so far are:".print_r($printed_warnings,1). ", new warning: |$message|</pre>", 'warning');
+		if (!in_array($message, $printed_warnings)) {
+			JFactory::getApplication()->enqueueMessage($message, 'error');
+			$printed_warnings[] = $message;
+		}
+		
+	}
 
 	/**
 	 * @return array
@@ -534,6 +547,7 @@ class plgVmShipmentRules_Shipping_Base extends vmPSPlugin {
 				$method->rule_name = $r->getRuleName($cartvals);
 				// If NoShipping is set, this method should NOT offer any shipping at all, so return FALSE, otherwise TRUE
 				if ($r->isNoShipping()) {
+					$this->printWarning(JText::sprintf('VMSHIPMENT_RULES_NOSHIPPING_MESSAGE', $method->rule_name));
 					vmdebug('checkConditions '.$method->shipment_name.' indicates NoShipping for rule "'.$method->rule_name.'" ('.$r->rulestring.').');
 					return FALSE;
 				} else {