refactor: use file_prepare_draft_area to load response files

It modifies the 'source' field, which other functions might depend on.

Closes: #219

Author: MHajoha

classes/local/attempt_ui/qpy_file_upload.php

@@ -136,17 +136,18 @@ private function render_writable(question_attempt $qa, question_ui_renderer $ren
         global $CFG, $PAGE, $USER;
         require_once($CFG->libdir . '/form/filemanager.php');
 
-        $draftitemid = file_get_unused_draft_itemid();
+        $combineddraftitemid = $renderer->prepare_combined_draft_area($qa);
+
         $rfs = di::get(response_file_service::class);
-        $rfs->prepare_draft_area($renderer->options->context->id, $qa, $this->name, $USER->id, $draftitemid);
+        $splitdraftitemid = $rfs->prepare_split_draft_area($this->name, $USER->id, $combineddraftitemid);
 
         // This is used to tell the qbehaviour what draft areas to save.
-        $renderer->draftareas[$this->name] = $draftitemid;
+        $renderer->draftareas[$this->name] = $splitdraftitemid;
 
         $limits = $this->get_limits_in($renderer->options->context);
 
         $fm = new form_filemanager((object)[
-            'itemid' => $draftitemid,
+            'itemid' => $splitdraftitemid,
             'subdirs' => false,
             'context' => $renderer->options->context,
             'maxfiles' => $limits->maxfiles,

classes/local/attempt_ui/question_ui_renderer.php

@@ -69,6 +69,9 @@ class question_ui_renderer {
      */
     public array $mappableduplicatefieldnames = [];
 
+    /** @var int $combineddraftitemid */
+    private int $combineddraftitemid = 0;
+
     /**
      * Private constructor. Use {@see question_ui_renderer::render()}.
      *
@@ -779,4 +782,27 @@ private function check_for_and_preserve_unknown_options(array $availableoptsinfo
         }
         return $warnings;
     }
+
+    /**
+     * Uses {@see file_prepare_draft_area} (indirectly) to copy all response files to a new draft area.
+     *
+     * We do this because {@see file_prepare_draft_area} does some possibly important and hard-to-rewrite magic concerning the
+     * file source.
+     *
+     * This is done lazily because read-only views won't need a draft area, and at most once because the draft area contains all
+     * field's files. When rendering the upload field, each element calls this method and then copies its own files in to a separate
+     * draft area.
+     *
+     * @param question_attempt $qa
+     * @return int
+     */
+    public function prepare_combined_draft_area(question_attempt $qa): int {
+        if (!$this->combineddraftitemid) {
+            $this->combineddraftitemid = $qa->prepare_response_files_draft_itemid(
+                constants::QT_VAR_RESPONSE_FILES,
+                $this->options->context->id
+            );
+        }
+        return $this->combineddraftitemid;
+    }
 }

classes/local/files/response_file_service.php

@@ -21,9 +21,8 @@
 use core\context;
 use file_exception;
 use Generator;
-use qtype_questionpy\constants;
+use moodle_exception;
 use qtype_questionpy\local\attempt_ui\qpy_file_upload;
-use question_attempt;
 use stored_file;
 use stored_file_creation_exception;
 
@@ -176,36 +175,39 @@ public static function filter_combined_files_for_field(array $files, string $fie
     }
 
     /**
-     * Out of the files belonging to a question attempt, copies the ones that belong to the given fieldname to the given draft area.
+     * From a draft area containing all response files, copies the ones belonging to the given fieldname to a new draft area.
      *
-     * @param int $contextid The attempt's context (not necessarily the question's). See {@see question_display_options::$context}.
-     * @param question_attempt $qa
      * @param string $fieldname
      * @param int $userid
-     * @param int $draftitemid
+     * @param int $combineddraftitemid
+     * @return int
+     * @throws moodle_exception
      * @throws coding_exception
      * @throws file_exception
      * @throws stored_file_creation_exception
      */
-    public function prepare_draft_area(
-        int $contextid,
-        question_attempt $qa,
+    public function prepare_split_draft_area(
         string $fieldname,
         int $userid,
-        int $draftitemid
-    ): void {
+        int $combineddraftitemid,
+    ): int {
+        $usercontext = context_user::instance($userid);
+        $resultdraftid = file_get_unused_draft_itemid();
+
         $fs = get_file_storage();
-        $allfiles = $qa->get_last_qt_files(constants::QT_VAR_RESPONSE_FILES, $contextid);
+        $allfiles = $fs->get_area_files($usercontext->id, 'user', 'draft', $combineddraftitemid, includedirs: false);
 
         foreach (self::filter_combined_files_for_field($allfiles, $fieldname) as $filename => $file) {
             $fs->create_file_from_storedfile([
                 'component' => 'user',
                 'filearea' => 'draft',
-                'itemid' => $draftitemid,
-                'contextid' => context_user::instance($userid)->id,
+                'itemid' => $resultdraftid,
+                'contextid' => $usercontext->id,
                 'filename' => $filename,
             ], $file);
         }
+
+        return $resultdraftid;
     }
 
     /**