Allow case sensitive validator/feedback function names. Issue #1792.

Author: sangwinc

stack/input/inputbase.class.php

@@ -209,8 +209,12 @@ protected function internal_construct() {
         if (trim($options ?? '') != '') {
             $options = explode(',', $options);
             foreach ($options as $option) {
-                $option = strtolower(trim($option));
                 [$option, $arg] = stack_utils::parse_option($option);
+                // Maintain back compatibility following fix to #1792.
+                $option = strtolower(trim($option));
+                if (!($option == 'validator' || $option == 'feedback')) {
+                    $arg = strtolower(trim($arg));
+                }
                 // Only accept those options specified in the array for this input type.
                 if (array_key_exists($option, $this->extraoptions)) {
                     if ($arg === '') {

tests/helper.php

@@ -4325,7 +4325,7 @@ public static function make_stack_question_validator() {
         // We need to check that local variable names within the block are not invalid for student's input.
         // We need to chack mathematics within the castext is correctly displayed.
         $q->questionvariables = 'texput(foo,lambda([e],[a,b]:args(e), sconcat("\\\\frac{", tex1(a), "}{", tex1(b), "}")));' .
-            'ta:phi^2-1;myvalidityidea(ex):=block(if ev(subsetp(setify(listofvars(ex)),' .
+            'ta:phi^2-1;myvalidityIdea(ex):=block(if ev(subsetp(setify(listofvars(ex)),' .
             'setify(listofvars(ta))), simp) then return(""),castext("[[lang code=\'fi\']]Vastauksesi sisältää ' .
             'vääriä muuttujia.[[/lang]][[lang code=\'en,other\']]Your answer {@ex@} contains the wrong variables.[[/lang]]"));';
         // This question is also used to test the lang blocks at the top level.
@@ -4346,7 +4346,7 @@ public static function make_stack_question_validator() {
             null,
             [
                 'boxWidth' => 20, 'forbidWords' => '', 'allowWords' => 'foo',
-                'options' => 'validator:myvalidityidea',
+                'options' => 'validator:myvalidityIdea',
             ]
         );