Checkboxes fieldtype in a form adds additional null value

[mmodler]

Bug description

In a form, we have a checkboxes fieldtype with one option. The relevant output of the field in frontend looks like this:

<input type="hidden" name="consent[]">
<input type="checkbox" name="consent[]" value="privacy_policy" required>

The saved submission data looks like this - expected but unintended in my opinion:

consent:
 - null
 - privacy_policy

I'm not sure if its better to filter out the null value server side or remove the hidden input.

How to reproduce

Save a form with a checkboxes fieldtype, check the saved data.

Logs

No response

Environment

Laravel Version: 10.35.0
PHP Version: 8.1.18
Antlers: runtime
Version: 4.40.0 PRO

Installation

Fresh statamic/statamic site via CLI

Antlers Parser

runtime (new)

Additional details

No response

[duncanmcclean]

What does your Antlers template look like for the form?

[mmodler]

Form:

<div class="form__form">
 <div class="form__text bard-text">
 {{ bard }}
 </div>
 {{ if success or errors }}
 <a id="form-{{ handle ?? form:handle }}" class="form__anchor"></a>
 <div class="form__alerts" >
 {{ if success }}
 {{ partial src="partials/alert" type="success" :messages="success" }}
 {{ elseif errors }}
 {{ partial src="partials/alert" type="error" :messages="errors" }}
 {{ /if }}
 </div>
 {{ /if }}

 <div class="form__fields">
 {{ fields }}
 {{ partial:partials/form_group }}
 {{ /fields }}
 </div>
 <div class="form__mandatory-fields"><small>* {{ 'Pflichtfelder' | trans }}</small></div>
 <input type="text" class="form__hp" name="{{ honeypot ?? 'honeypot' }}">
 <div class="form__actions">
 <button type="submit" class="button">Abschicken</button>
 </div>
</div>

Partial:

<div class="form__group form__group--{{ type }} form__group--w{{ width }}{{ if validate | contains('required') }} is-required{{ /if }}{{ if error }} has-danger{{ /if }}">
 <label class="form__label">{{ display | sanitize }}</label>
 {{ if instructions and instructions_position != 'below'}}
 <div class="form__description">{{ instructions }}</div>
 {{ /if }}
 <div class="form__field">{{ field }}</div>
 {{ if instructions and instructions_position == 'below'}}
 <div class="form__description">{{ instructions }}</div>
 {{ /if }}
</div>

But the hidden input comes from statamic core in resources/views/extend/forms/fields/checkboxes.antlers.html Line 1:

<input type="hidden" name="{{ handle }}[]">
{{ foreach:options as="option|label" }}
 <label>
 <input
 type="checkbox"
 name="{{ handle }}[]"
 value="{{ option }}"
 {{ if js_driver }}{{ js_attributes }}{{ /if }}
 {{ if value|in_array:option }}checked{{ /if }}
 {{ if validate|contains:required }}required{{ /if }}
 >
 {{ label !== null ? label : option }}
 </label>
 {{ unless inline }}
 <br>
 {{ /unless }}
{{ /foreach:options }}