MDL-35147 lesson: fix regression from MDL-25492.

I really wish someone would fix lesson to use the question bank.

mod/lesson/format.php

@@ -580,6 +580,93 @@ class qformat_default {
         return html_to_text(format_text($question->questiontext,
                 $question->questiontextformat, $formatoptions), 0, false);
     }
+
+    /**
+     * Since the lesson module tries to re-use the question bank import classes in
+     * a crazy way, this is necessary to stop things breaking.
+     */
+    protected function add_blank_combined_feedback($question) {
+        return $question;
+    }
 }
 
 
+/**
+ * Since the lesson module tries to re-use the question bank import classes in
+ * a crazy way, this is necessary to stop things breaking. This should be exactly
+ * the same as the class defined in question/format.php.
+ */
+class qformat_based_on_xml extends qformat_default {
+    /**
+     * A lot of imported files contain unwanted entities.
+     * This method tries to clean up all known problems.
+     * @param string str string to correct
+     * @return string the corrected string
+     */
+    public function cleaninput($str) {
+
+        $html_code_list = array(
+            "'" => "'",
+            "’" => "'",
+            "“" => "\"",
+            "”" => "\"",
+            "–" => "-",
+            "—" => "-",
+        );
+        $str = strtr($str, $html_code_list);
+        // Use textlib entities_to_utf8 function to convert only numerical entities.
+        $str = textlib::entities_to_utf8($str, false);
+        return $str;
+    }
+
+    /**
+     * Return the array moodle is expecting
+     * for an HTML text. No processing is done on $text.
+     * qformat classes that want to process $text
+     * for instance to import external images files
+     * and recode urls in $text must overwrite this method.
+     * @param array $text some HTML text string
+     * @return array with keys text, format and files.
+     */
+    public function text_field($text) {
+        return array(
+            'text' => trim($text),
+            'format' => FORMAT_HTML,
+            'files' => array(),
+        );
+    }
+
+    /**
+     * Return the value of a node, given a path to the node
+     * if it doesn't exist return the default value.
+     * @param array xml data to read
+     * @param array path path to node expressed as array
+     * @param mixed default
+     * @param bool istext process as text
+     * @param string error if set value must exist, return false and issue message if not
+     * @return mixed value
+     */
+    public function getpath($xml, $path, $default, $istext=false, $error='') {
+        foreach ($path as $index) {
+            if (!isset($xml[$index])) {
+                if (!empty($error)) {
+                    $this->error($error);
+                    return false;
+                } else {
+                    return $default;
+                }
+            }
+
+            $xml = $xml[$index];
+        }
+
+        if ($istext) {
+            if (!is_string($xml)) {
+                $this->error(get_string('invalidxml', 'qformat_xml'));
+            }
+            $xml = trim($xml);
+        }
+
+        return $xml;
+    }
+}