Problems with isDate validator

[patrickatwsrn]

Bug report

isDate validator is returning true for some dates that are not valid.

Summary

core/components/formit/src/FormIt/Validator.php, line #658

    public function isDate($key, $value, $format = '%m/%d/%Y')
    {
        /* allow empty isDate, :required should be used to prevent blank field */
        if (empty($value)) {
            return true;
        }
        $ts = strtotime($value);
        if ($ts === false) {
            return $this->_getErrorMessage($key,'vTextIsDate','formit.not_date',array(
                'format' => $format,
                'field' => $key,
                'value' => $value,
            ));
        }
        if (!empty($format)) {
            $this->fields[$key] = strftime($format,$ts);
        }
        return true;
    }

strtotime is not a sufficient way to validate a date string because it is "fixing" problems it should not.

Step to reproduce

Simple snippet to test if there is a February 29th in a given year:

<?php 
# Name:  testDate snippet
# Usage: [[!testDate? &input=`2020-02-29`]]

if(strtotime($input)) {
   return date('Y-m-d',strtotime($input));
}
else {
   return "false";
}

2020 was a leap year.

• Input: 2020-02-29
• Output: 2020-02-29
• Error: No

2021 was NOT a leap year

• Input: 2021-02-29
• Output: 2021-03-03
• Error: Yes !!!

Every day <= 31 returns for february a day in the next month

• Input: 2021-02-31
• Output: 2021-03-01 !!!
• Error: Yes

It does the right thing if it encounters impossible dates:

• Input: 2020-13-01
• Output: false
• Error: No

Observed behavior

Validation of dates within the bounderies of february is not trustworthy.

Expected behavior

Dates within the scope of february should be handled in a proper way.

The php function checkdate() might be helpful here.

Docs: https://www.php.net/manual/en/function.checkdate.php

Environment

MODX 2.8.1, Formit 4.2.6 , PHP 7.4.18, Apache Webserver Running on Ubuntu Linux.

[patrickatwsrn]

Something like this shold do the trick:

    function isValidDate(string $date, string $format = 'Y-m-d'){
        // php 
        $dateObj = DateTime::createFromFormat($format, $date);
        return $dateObj && $dateObj->format($format) == $date;
    }