Django自定义过滤器未在标签库中注册

Question

I've written the following filter (in templatetags/custom_errors.py ):

from django import template
from django.utils.safestring import mark_safe

register = template.Library()


@register.filter
def custom_errors(bound_field):
    return mark_safe(f'<span id="{bound_field.id_for_label}-error" class="error">{", ".join(bound_field.errors)}</span>' if bound_field.errors else '')

which I'm trying to use in a template as follows:

{% load widget_tweaks %}
{% load custom_errors %}
{% load label_with_classes %}
{% csrf_token %}

<div class="row">
  <div class="input-field col s12">
    {{ form.session_number|add_error_class:"invalid" }}
    {{ form.session_number|custom_errors }}
    {{ form.session_number|label_with_classes }}
  </div>
</div>

However, I'm getting a TemplateSyntaxError : 'custom_errors' is not a registered tag library :

What puzzles me, however, is that some of the tags that are registered, such as label_with_classes , are done so in the same way. Here is a tree view of dashboard/templatetags :

dashboard/templatetags
├── active_page.py
├── custom_errors.py
├── edit_view_family_heading.py
├── google_analytics.py
├── label_with_classes.py
├── order_link.py
├── paginator.py
└── profile_badge.py

showing that label_with_classes.py is in the same directory as custom_errors.py . Here are the contents of label_with_classes.py :

from django import template
from django.forms import ChoiceField, BooleanField, DateField
from titlecase import titlecase

register = template.Library()


def pretty_name(name):
    """Convert 'first_name' to 'First Name'."""
    return titlecase(name.replace('_', ' '))


@register.filter(is_safe=True)
def label_with_classes(bound_field, contents=None):
    '''Extend Django's label_tag() method to provide the appropriate Materialize CSS classes'''
    # The field should have the 'active' class if it has a value (see http://materializecss.com/forms.html),
    # except for ChoiceFields (which include ModelChoiceFields and MultipleChoiceFields) and BooleanFields
    should_be_active = (bound_field.value() and not isinstance(bound_field.field, (ChoiceField, BooleanField)))\
                       or isinstance(bound_field.field, DateField)
    active = 'active' if should_be_active else ''
    invalid = 'invalid' if bound_field.errors else ''
    classes = f"{active} {invalid}".strip()
    contents = contents or pretty_name(bound_field.name)
    return bound_field.label_tag(
        attrs={'class': classes},
        contents=contents,
        label_suffix='')

I don't see any difference in the ways both filters are registered (except that one has is_safe=True and the other doesn't). Why is the custom_errors filter not registering? Is there some kind of caching issue?

Answer 1

The terminal from which I was running python manage.py runserver had somehow become unresponsive and wasn't responding to Cntrl+C. I terminated the process and restarted the development server, and now things work as expected.