Django i18n gives incomplete translations

Question

I am facing a problem with django translation. Some strings of my .po files doesn't appear when the server runs. I mean some translations are displayed some others are not. wether they appears or not, they are both listed in the django.po file. it's not a question of "fuzzy" tags, as a I removed them. It's seem not to be a question of empty quotes following very long msgid or msgstr. The only reason of that bad translation display are the format_html() function which allow to type a longer help text. Do you have any idea on how I can solve this case ?

apps/survey/forms.py

from django import forms
from django.utils.translation import ugettext_lazy as _
from django.utils.html import format_html
from django.forms.widgets import NumberInput
from survey.models import Survey2019

class Survey2019Form(forms.ModelForm):
    class Meta:
        model = Survey2019
    ...
    lines = forms.IntegerField(
        label=_('Lines'),
        help_text= _("What is the average number of lines contained in your reports ?"),
        widget=NumberInput(attrs={'type':'range', 'step': '1', 'min':'0', 'max':'500', 'step':'5'}),
        initial=0
        )

    categories = forms.IntegerField(
        label=_('Categories'),
        help_text= format_html("{}<br>{}<br>{}<br>{}",
            _("What is the average number of categories or dimensions in your reports ?"),
            _("Categories are mostly not numeric data."),
            _("They can't be computed but provide qualitative informations."),
            _(" For exemple : geographic areas, colors or groups of products...")),
        widget=NumberInput(attrs={'type':'range', 'min':'0', 'max':'100', 'step':'1'}),
        initial=0
        )
    ...

locale/fr/LC_MESSAGES/django.po

    ...
    : apps/survey/forms.py:80
msgid "Lines"
msgstr "lignes"

#: apps/survey/forms.py:81
msgid "What is the average number of lines contained in your reports ?"
msgstr "Quel est le nombre moyen de lignes que comptent vos tableaux de bord ?"


#: apps/survey/forms.py:87
msgid "Categories"
msgstr "Catégories"

#: apps/survey/forms.py:89
msgid "What is the average number of categories or dimensions in your reports ?"
msgstr "Quel est le nombre moyen de catégories que comptent vos tableaux de bord ?"

#: apps/survey/forms.py:90
msgid "Categories are mostly not numeric data."
msgstr "les catégories, ou dimensions, sont souvent des données non numériques"

#: apps/survey/forms.py:91
msgid "They can't be computed but provide qualitative informations."
msgstr "Elles ne peuvent-être calculée mais fournissent des informations qualitatives"

#: apps/survey/forms.py:92
msgid " For exemple : geographic areas, colors or groups of products..."
msgstr ""
"par exemple des zones géographiques, des couleurs, des groupes de produits "
"ou de personnes"
....

survey2019.html

...
{% for field in fillform.visible_fields  %}
<div class="{% if forloop.first %}card{% else %}d-none {% endif %} fl-w-600 fl-h-700 justify-content-between align-items-center" id="id_question_{{forloop.counter}}" refer="id_{{field.name}}">
  <div class="w-100 fl-h-50 fl-bg-prune">
    <h2 class="flowka fl-txt-white text-truncate text-center pt-1">{{field.label}}</h2>
  </div>
  <div class="fl-h-500 p-2 w-100">
    <div class="text-justify p-2 fl-txt-prune fl-txt-md mb-1" style="margin-top:-30px;">
      {{ field.help_text }}
    </div>
    ...  
  </div>
  ...
</div>
{% endfor %} 

Answer 1

As I ssupected it, the problem comes from the format_html() function and the need of lazy translation. The ugettext_lazy() function does not works with format_html(). It needs a format_html_lazy()

core/utils.py

from django.utils.functional import lazy
from django.utils.html import format_html

format_html_lazy = lazy(format_html, str)

and I changed the call of format_html() in forms.py and models.py

forms.py

from core.utils import format_html_lazy as format_html

et voilà !