Modifying bootstrap 4 label for checkbox removes the actual input element

[ThePeterMick]

Symfony version(s) affected: 4.1.4

Description
If you try to override only a label of a checkbox, the input element disappears.

The custom label is shown once if using ‘form_widget’ and twice if using ‘form_row’, the actual checkbox/input never appears, just the label.

How to reproduce
Use in a twig view:

{% form_theme form _self %}

{% block _user_registration_form_termsAccepted_label %}
    <label class="form-check-label required" for="user_registration_form_termsAccepted">{{ 'label.terms_accepted'|trans({ '%terms_and_conditions_link%': path('terms') })|raw }}</label>
{% endblock %}

Render via {{ form_widget(form.termsAccepted) }} - shows the label once, with an indent (form-check div wrap)
Render via {{ form_row(form.termsAccepted) }} - shows the label twice, one without an indent and second with an indent same as with form_widget

Possible Solution

Additional context

[xabbuh]

Can you check if #26540 is the same?

[ThePeterMick]

@xabbuh nope it isn’t, what #26540 relates to appears to be an expected behaviour according to the docs, will comment there

[xabbuh]

But, the reason is the same, isn't it? I mean the fact that the label is rendered by the widget. This means your custom label won't be shown with form_widget() while form_row() displays your own label as well as the one rendered by the widget. Isn't that what's happening?

[ThePeterMick]

My custom label is shown with both, as described in the first post above:

“Render via {{ form_widget(form.termsAccepted) }} - shows the label once, with an indent (form-check div wrap)
Render via {{ form_row(form.termsAccepted) }} - shows the label twice, one without an indent and second with an indent same as with form_widget”

The issue here is the actual widget / input disappears here in both scenarios, and additionally with form_row the label is shown twice.

This and the other issue are not the same.

[ThePeterMick]

I’ve updated the original issue description above to hopefully make this clearer.

[xabbuh]

👍 I think I understand the issue now. I am looking into it.

[ThePeterMick]

Thank you @xabbuh, please let me know if you need anything tested :-)