feat: implement is_same_response

Author: MHajoha

classes/utils.php

@@ -127,4 +127,15 @@ public static function reindex_integer_arrays(array &$array): void {
             $array = array_values($array);
         }
     }
+
+    /**
+     * Given an array as returned by {@see \question_attempt_step::get_qt_data()}, filters out vars starting with `_`.
+     *
+     * @param array $qtvars
+     * @return array
+     * @see question_attempt_step for the meaning of different step var prefixes
+     */
+    public static function filter_for_response(array $qtvars): array {
+        return array_filter($qtvars, fn($key) => !str_starts_with($key, '_'), ARRAY_FILTER_USE_KEY);
+    }
 }

question.php

@@ -24,8 +24,8 @@
 
 use qtype_questionpy\api\api;
 use qtype_questionpy\api\attempt_ui;
-use qtype_questionpy\constants;
 use qtype_questionpy\api\scoring_code;
+use qtype_questionpy\constants;
 use qtype_questionpy\question_ui_metadata_extractor;
 use qtype_questionpy\utils;
 
@@ -267,7 +267,7 @@ public function is_complete_response(array $response): bool {
     }
 
     /**
-     * Use by many of the behaviours to determine whether the student's
+     * Used by many of the behaviours to determine whether the student's
      * response has changed. This is normally used to determine that a new set
      * of responses can safely be discarded.
      *
@@ -277,8 +277,10 @@ public function is_complete_response(array $response): bool {
      * @return bool whether the two sets of responses are the same - that is
      *                            whether the new set of responses can safely be discarded.
      */
-    public function is_same_response(array $prevresponse, array $newresponse) {
-        return false;
+    public function is_same_response(array $prevresponse, array $newresponse): bool {
+        // The response has already been filtered against get_expected_data, we just need to filter out attempt state
+        // and scoring state before comparing.
+        return utils::filter_for_response($prevresponse) == utils::filter_for_response($newresponse);
     }
 
     /**