Bug: Custom validation error is cleared when setting rule twice

[tsomeq]

PHP Version

7.4

CodeIgniter4 Version

4.2.1

CodeIgniter4 Installation Method

Composer (using codeigniter4/appstarter)

Which operating systems have you tested for this bug?

Linux

Which server did you use?

fpm-fcgi

Database

No response

What happened?

Using the Built-in Validation class,
custom validation error message previously set is cleared when setting another rule.

Steps to Reproduce

$va = \Config\Services::validation();
$va->setRule("field1", "Field 1", ["required"], ["required" => "You must input field 1"] );
$va->setRule("field2", "Field 2", ["required"], ["required" => "You must input field 2"] );
$va->run([]);
$errors = $va->getErrors();
echo $errors["field1"] . "/" . $errors["field2"];

Expected Output

You must input field 1/You must input field 2

but

The field1 is required. / You must input field 2

Anything else?

It seems that the setRule() method calls getRules() internally to get rules already set, but it does not supply customErrors.

[kenjis]

Thank you for good bug reporting.

I sent a PR #6241
Please check if you can.