我的自定义主题bootstrap_4_layout如下所示：
{% extends "bootstrap_4_layout.html.twig" %}
{# this is basically the default form_label block, but with the form_error block definition removed, see line 260 of bootstrap_4_layout.html.twig #}
{% block form_label -%}
{# I think you can safely remove this if-statement, you currently might end up with 2 errors when you have a form with no label defined. #}
{% if label is not same as(false) -%}
{%- if compound is defined and compound -%}
{%- set element = 'legend' -%}
{%- set label_attr = label_attr|merge({class: (label_attr.class|default('') ~ ' col-form-label')|trim}) -%}
{%- else -%}
{%- set label_attr = label_attr|merge({for: id}) -%}
{%- endif -%}
{% if required -%}
{% set label_attr = label_attr|merge({class: (label_attr.class|default('') ~ ' required')|trim}) %}
{%- endif -%}
{% if label is empty -%}
{%- if label_format is not empty -%}
{% set label = label_format|replace({
'%name%': name,
'%id%': id,
}) %}
{%- else -%}
{% set label = name|humanize %}
{%- endif -%}
{%- endif -%}
<{{ element|default('label') }}{% if label_attr %}{% with { attr: label_attr } %}{{ block('attributes') }}{% endwith %}{% endif %}>
{%- if translation_domain is same as(false) -%}
{%- if label_html is same as(false) -%}
{{- label -}}
{%- else -%}
{{- label|raw -}}
{%- endif -%}
{%- else -%}
{%- if label_html is same as(false) -%}
{{- label|trans(label_translation_parameters, translation_domain) -}}
{%- else -%}
{{- label|trans(label_translation_parameters, translation_domain)|raw -}}
{%- endif -%}
{%- endif -%}
{# here was the form_errors call which is now gone #}</{{ element|default('label') }}>
{%- else -%}
{%- if errors|length > 0 -%}
<div id="{{ id }}_errors" class="mb-2">
{{- form_errors(form) -}}
</div>
{%- endif -%}
{%- endif -%}
{%- endblock form_label %}
{# here, we're adding the form_errors(form) call we just removed from the form_label block, so the error is in the correct position #}
{% block form_row -%}
{%- if compound is defined and compound -%}
{%- set element = 'fieldset' -%}
{%- endif -%}
{%- set widget_attr = {} -%}
{%- if help is not empty -%}
{%- set widget_attr = {attr: {'aria-describedby': id ~"_help"}} -%}
{%- endif -%}
<{{ element|default('div') }}{% with {attr: row_attr|merge({class: (row_attr.class|default('') ~ ' form-group')|trim})} %}{{ block('attributes') }}{% endwith %}>
{{- form_label(form) -}}
{{- form_widget(form, widget_attr) -}}
{{- form_help(form) -}}
{{- form_errors(form) -}} {# << here :-) #}
</{{ element|default('div') }}>
{%- endblock form_row %}
通常，此代码在输入下呈现错误标签，默认在上面。
每个错误都被渲染得很好，但在复选框上，它被渲染了两次： 在此处输入图像描述
