Symfony version(s) affected

7.0.3

Description

Related to #53976 (which is basically the same for id attributes)

The checks being performed on the names of form fields are still following the HTML4 specs.
However, they changed in HTML5 - the only forbidden names are now:

• empty string
• isindex
• _charset_ (case-insensitive)

Source: https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#attr-fe-name

So I suggest to adjust the check.

How to reproduce

Setup a form with:

public function getBlockPrefix(): string
{
    return '-foo';
}

Resulting error:

The name "-foo" contains illegal characters. Names should start with a letter, digit or underscore and only contain letters, digits, numbers, underscores ("_"), hyphens ("-") and colons (":").

Possible Solution

The check is happening in FormConfigBuilder::isValidName()

Additional Context

No response