Django filters. is_safe doesn't work

Question

In my app teams/templatetags/teams_extras.py I have this filter

from django import template

register = template.Library()

@register.filter(is_safe=True)
def quote(text):
    return "« {} »".format(text)

So I use it into my view teams/templates/teams/show.html

{% extends './base.html' %}
{% load static %}
{% load teams_extras %}
...
<b>Bio :</b> {{ team.biography|quote }}
...

But this is the result on my page:

&laquo; <p>The Miami Heat are an American professional basketball team based in Miami. The Heat compete in the National Basketball Association as a member of the league's Eastern Conference Southeast Division</p> &raquo; 

Why ? Thank you

Answer 1

Doc says:

This flag tells Django that if a “safe” string is passed into your filter, the result will still be “safe” and if a non-safe string is passed in, Django will automatically escape it, if necessary.

So try to pass safe value into your filter:

{{ team.biography|safe|quote }}

or user mark_safe:

from django.utils.safestring import mark_safe

@register.filter()
def quote(text):
    return mark_safe("« {} »".format(text))

And:

{{ team.biography|quote }}

This should works.