Questions: add min-length to string/text type questions (#6488)

* Questions: add min-length to string/text type questions

* fix test

src/pretix/api/serializers/item.py

@@ -550,7 +550,7 @@ class QuestionSerializer(I18nAwareModelSerializer):
                   'ask_during_checkin', 'show_during_checkin', 'identifier', 'dependency_question', 'dependency_values',
                   'hidden', 'dependency_value', 'print_on_invoice', 'help_text', 'valid_number_min',
                   'valid_number_max', 'valid_date_min', 'valid_date_max', 'valid_datetime_min', 'valid_datetime_max',
-                  'valid_string_length_max', 'valid_file_portrait')
+                  'valid_string_length_max', 'valid_string_length_min', 'valid_file_portrait')
 
     def validate_identifier(self, value):
         Question._clean_identifier(self.context['event'], value, self.instance)

src/pretix/base/forms/questions.py

@@ -708,6 +708,7 @@ class BaseQuestionsForm(forms.Form):
         elif q.type == Question.TYPE_STRING:
             field = forms.CharField(
                 label=escape(q.question), required=required,
+                min_length=q.valid_string_length_min,
                 max_length=q.valid_string_length_max,
                 help_text=rich_text(q.help_text),
                 initial=initial.answer if initial else None,
@@ -715,6 +716,7 @@ class BaseQuestionsForm(forms.Form):
         elif q.type == Question.TYPE_TEXT:
             field = forms.CharField(
                 label=escape(q.question), required=required,
+                min_length=q.valid_string_length_min,
                 max_length=q.valid_string_length_max,
                 help_text=rich_text(q.help_text),
                 widget=forms.Textarea,

src/pretix/base/migrations/0310_question_valid_string_length_min.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.2.12 on 2026-08-19 11:31
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("pretixbase", "0309_alter_questionanswer_unique_together_and_more"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="question",
+            name="valid_string_length_min",
+            field=models.PositiveIntegerField(null=True),
+        ),
+    ]

src/pretix/base/models/items.py

@@ -50,7 +50,7 @@ from dateutil.tz import datetime_exists
 from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.core.validators import (
-    MaxLengthValidator, MinValueValidator, RegexValidator,
+    MaxLengthValidator, MinLengthValidator, MinValueValidator, RegexValidator,
 )
 from django.db import models
 from django.db.models import Q
@@ -1731,6 +1731,11 @@ class Question(LoggedModel):
     valid_datetime_max = models.DateTimeField(null=True, blank=True,
                                               verbose_name=_('Maximum value'),
                                               help_text=_('Currently not supported in our apps and during check-in'))
+    valid_string_length_min = models.PositiveIntegerField(null=True, blank=True,
+                                                          verbose_name=_('Minimum length'),
+                                                          help_text=_(
+                                                              'Currently not supported in our apps and during check-in'
+                                                          ))
     valid_string_length_max = models.PositiveIntegerField(null=True, blank=True,
                                                           verbose_name=_('Maximum length'),
                                                           help_text=_(
@@ -1885,6 +1890,11 @@ class Question(LoggedModel):
             else:
                 raise ValidationError(_('Unknown country code.'))
         elif self.type in (Question.TYPE_STRING, Question.TYPE_TEXT):
+            if self.valid_string_length_min is not None and len(answer) < self.valid_string_length_min:
+                raise ValidationError(MinLengthValidator.message % {
+                    'limit_value': self.valid_string_length_min,
+                    'show_value': len(answer)
+                })
             if self.valid_string_length_max is not None and len(answer) > self.valid_string_length_max:
                 raise ValidationError(MaxLengthValidator.message % {
                     'limit_value': self.valid_string_length_max,
@@ -1906,6 +1916,8 @@ class Question(LoggedModel):
             raise ValidationError(_("The maximum date must not be before the minimum value."))
         if self.valid_number_max and self.valid_number_min and self.valid_number_min > self.valid_number_max:
             raise ValidationError(_("The maximum value must not be lower than the minimum value."))
+        if self.valid_string_length_max and self.valid_string_length_min and self.valid_string_length_min > self.valid_string_length_max:
+            raise ValidationError(_("The maximum length must not be shorter than the minimum length."))
         super().clean()
 
     def clean_type_change(self, old_type, new_type):

src/pretix/control/forms/item.py

@@ -251,6 +251,7 @@ class QuestionForm(I18nModelForm):
             'valid_date_min',
             'valid_date_max',
             'valid_file_portrait',
+            'valid_string_length_min',
             'valid_string_length_max',
         ]
         widgets = {

src/pretix/control/templates/pretixcontrol/items/question_edit.html

@@ -47,6 +47,7 @@
                     {% bootstrap_field form.valid_datetime_max layout="control" %}
                 </div>
                 <div id="valid-string">
+                    {% bootstrap_field form.valid_string_length_min layout="control" %}
                     {% bootstrap_field form.valid_string_length_max layout="control" %}
                 </div>
                 <div id="valid-file">