ISLANDORA-581 On content model trigered tabs we use module_exists to verify if a module is present and enabled before calling code. We also use module_load_include instead of including directly.

ContentModel.inc

@@ -1475,19 +1475,30 @@ class ContentModel extends XMLDatastream {
                 self::$errors[] = 'Execute Form Handler: file \'' . $path . '\' does not exist.';
               }
               else {
-                require_once($path);
-                $className = $method->getAttribute('class');
-                $methodName = ($method->getAttribute('method'));
-                if (!class_exists($className)) {
-                  self::$errors[] = 'Execute Form Handler: class \'' . $className . '\' does not exist.';
-                }
-                else {
-                  $class = new $className($pid);
-                  if (!method_exists($class, $methodName)) {
-                    self::$errors[] = 'Execute Form Handler: method \'' . $className . '->' . $methodName . '\' does not exist.';
+
+                $file_extension = pathinfo($method->getAttribute('file'), PATHINFO_EXTENSION);
+                $file_path_without_extension = $method->getAttribute('file');
+                /* Only in PHP. This is meant to avoid file path
+                 * concatenation issues.*/
+                $file_path_without_extension = substr($file_path_without_extension, 0, strlen($file_path_without_extension) - (strlen($file_extension) + 1));
+                /* Only try to execute if the module is present, this is
+                 * necessarybecause we go outside of the expected
+                 * 'Drupal Way' and have dynamic dependencies.*/
+                if (module_exists(!empty($module) ? $module : 'fedora_repository')) {
+                  module_load_include($file_extension, !empty($module) ? $module : 'fedora_repository', $file_path_without_extension);
+                  $className = $method->getAttribute('class');
+                  $methodName = ($method->getAttribute('method'));
+                  if (!class_exists($className)) {
+                    self::$errors[] = 'Execute Form Handler: class \'' . $className . '\' does not exist.';
                   }
                   else {
-                    $output = $class->$methodName($page_number);
+                    $class = new $className($pid);
+                    if (!method_exists($class, $methodName)) {
+                      self::$errors[] = 'Execute Form Handler: method \'' . $className . '->' . $methodName . '\' does not exist.';
+                    }
+                    else {
+                      $output = $class->$methodName($page_number);
+                    }
                   }
                 }
               }