Language choices: not in User.model

Having this as a model field is "annoying" because each added language
will trigger a (potentially costly) migration even though no real database
work is actually done for it.

Also implements a selector that shows languages in both their own language
and the currently activated language.

Correct spelling to "zh-hans" (lowercase); see https://stackoverflow.com/a/7729311

See #161

users/forms.py

@@ -9,7 +9,9 @@ from django.core.exceptions import ValidationError
 from django.contrib.auth import password_validation
 from django.forms import ModelForm
 from django.utils.html import escape, mark_safe
-from django.utils.translation import gettext_lazy as _
+from django.utils.translation import gettext_lazy as _, get_language_info
+from django.conf import settings
+
 
 TRUE_FALSE_CHOICES = (
     (True, _("Yes")),
@@ -131,6 +133,18 @@ class SetPasswordForm(BaseSetPasswordForm):
         self.fields['new_password2'].help_text = None  # "Confirm password" is descriptive enough
 
 
+def language_choices():
+    items = [("auto", _("Auto (browser preference)"))]
+
+    for code, _label in settings.LANGUAGES:
+        info = get_language_info(code)
+        label = info["name_local"] \
+            if info["name_local"] == info["name_translated"] \
+            else f"{info['name_local']} ({info['name_translated']})"
+        items.append((code, label))
+    return items
+
+
 class PreferencesForm(ModelForm):
     # I haven't gotten a decent display for checkboxes in forms yet; the quickest hack around this is a ChoiceField
     send_email_alerts = forms.ChoiceField(
@@ -143,7 +157,7 @@ class PreferencesForm(ModelForm):
     )
     language = forms.ChoiceField(
         label=_("Language"),
-        choices=User.LANGUAGE_CHOICES,
+        choices=language_choices,
         required=True,
         widget=forms.Select(),
     )

users/migrations/0003_user_language.py

@@ -1,18 +1,16 @@
-# Generated by Django 4.2.23 on 2025-07-28 09:27
-
 from django.db import migrations, models
 
 
 class Migration(migrations.Migration):
 
     dependencies = [
-        ('users', '0002_user_theme_preference'),
+        ("users", "0002_user_theme_preference"),
     ]
 
     operations = [
         migrations.AddField(
-            model_name='user',
-            name='language',
-            field=models.CharField(choices=[('auto', 'Auto'), ('en', 'English'), ('zh-Hans', 'Simplified Chinese')], default='auto', max_length=10),
+            model_name="user",
+            name="language",
+            field=models.CharField(default="auto", max_length=10),
         ),
     ]

users/models.py

@@ -28,15 +28,11 @@ class User(AbstractUser):
         default="system",
         blank=False,
     )
-
-    LANGUAGE_CHOICES = [
-        ("auto", _("Auto")),
-        ("en", _("English")),
-        ("zh-Hans", _("Simplified Chinese")),
-    ]
     language = models.CharField(
         max_length=10,
-        choices=LANGUAGE_CHOICES,
+        # choices intentionally not set, we don't want changes to trigger migrations; the actual choices are set in
+        # forms.py; in Django 5.0 and up we can instead used a callable here
+        # choices=...
         default="auto",
         blank=False,
     )