MDL-72744 core_grades: Escape formulas when exporting spreadsheets

public/lib/csvlib.class.php

@@ -449,6 +449,9 @@ class csv_export_writer {
             }
         }
         $delimiter = csv_import_reader::get_delimiter($this->delimiter);
+        foreach ($row as $key => $value) {
+            $row[$key] = \core\dataformat::escape_spreadsheet_formula($value);
+        }
         fputcsv($this->fp, $row, $delimiter, $this->csvenclosure, '\\');
     }
 

public/lib/excellib.class.php

@@ -207,6 +207,7 @@ class MoodleExcelWorksheet {
         $col += 1;
 
         $celladdress = CellAddress::fromColumnAndRow($col, $row + 1);
+        $str = \core\dataformat::escape_spreadsheet_formula($str);
 
         $this->worksheet->getStyle($celladdress)->getNumberFormat()->setFormatCode(NumberFormat::FORMAT_TEXT);
         $this->worksheet->getCell($celladdress)->setValueExplicit($str, DataType::TYPE_STRING);

public/lib/odslib.class.php

@@ -164,6 +164,8 @@ class MoodleODSWorksheet {
         if (is_array($format)) {
             $format = new MoodleODSFormat($format);
         }
+        $str = \core\dataformat::escape_spreadsheet_formula($str);
+
         $this->data[$row][$col]->value = $str;
         $this->data[$row][$col]->type = 'string';
         $this->data[$row][$col]->format = $format;