MDL-54802 mod_quiz: Improve validation when editing a quiz uusing req…

…uire passing grade

When editing a quiz that is using the require passing grade completion method,
the grade to pass cannot be zero. Since the completion method is locked we
cannot recommend that the completion method is changed (as we do when the quiz
is being created). Instead we have to inform the user that the grade to pass
must not be zero.

mod/quiz/lang/en/quiz.php

@@ -400,6 +400,7 @@
 $string['gradesdeleted'] = 'Quiz grades deleted';
 $string['gradesofar'] = '{$a->method}: {$a->mygrade} / {$a->quizgrade}.';
 $string['gradetopassnotset'] = 'This quiz does not have a grade to pass set so you cannot use this option. Please use the require grade setting instead.';
+$string['gradetopassmustbeset'] = 'Grade to pass cannot be zero as this quiz has its completion method set to require passing grade. Please set a non-zero value.';
 $string['gradingdetails'] = 'Marks for this submission: {$a->raw}/{$a->max}.';
 $string['gradingdetailsadjustment'] = 'With previous penalties this gives <strong>{$a->cur}/{$a->max}</strong>.';
 $string['gradingdetailspenalty'] = 'This submission attracted a penalty of {$a}.';

mod/quiz/mod_form.php

@@ -534,9 +534,15 @@ public function validation($data, $files) {
         }
 
         if (array_key_exists('completion', $data) && $data['completion'] == COMPLETION_TRACKING_AUTOMATIC) {
+            $completionpass = isset($data['completionpass']) ? $data['completionpass'] : $this->current->completionpass;
+
             // Show an error if require passing grade was selected and the grade to pass was set to 0.
-            if ($data['completionpass'] == 1 && (empty($data['gradepass']) || grade_floatval($data['gradepass']) == 0)) {
-                $errors['completionpassgroup'] = get_string('gradetopassnotset', 'quiz');
+            if ($completionpass && (empty($data['gradepass']) || grade_floatval($data['gradepass']) == 0)) {
+                if (isset($data['completionpass'])) {
+                    $errors['completionpassgroup'] = get_string('gradetopassnotset', 'quiz');
+                } else {
+                    $errors['gradepass'] = get_string('gradetopassmustbeset', 'quiz');
+                }
             }
         }