[Form] form_row does not pass variable to form_widget

my template

 {{ form_row (form.sku, { 'attr': { 'placeholder': 'Sku'} }) }}

fields.html.twig

{% extends 'form_div_layout.html.twig' %}

{% block field_row %}
{% spaceless %}
<div class="form-row">
    {{ form_label(form) }}
    {{ form_errors(form) }}
    {{ form_widget(form, attr) }}
    {% debug attr %}
</div>
{% endspaceless %}
{% endblock field_row %}

{% block field_widget %}
{% debug attr %}
{% spaceless %}
{% set type = type|default('text') %}
<input class="form-{{ type }}" type="{{ type }}" {{ block('widget_attributes') }} {% if value is not empty %}value="{{ value }}" {% endif %}/>
{% endspaceless %}
{% endblock field_widget %}

as you see i pass var attr from form_row to form_widget
{{ form_widget(form, attr) }}

{% debug attr %} in field_row outputs array(1) { ["placeholder"]=> string(5) "Sku" }
{% debug attr %} in widget_row outputs array(0) { }

P.S. I'm aware of

 {{ form_widget (form.sku, { 'attr': { 'placeholder': 'Sku'} }) }}

[phiamo]

hi came over the same issue , try this: for me it works:

{% block field_row %}
{% spaceless %}
<div class="form-row">
    {{ form_label(form) }}
    {{ form_errors(form) }}
    {{ form_widget(form, {'attr': attr}) }}
    {% debug attr %}
</div>
{% endspaceless %}
{% endblock field_row %}

[vicb]

Closing this issue as the solution has been provided by @phiamo.