Fixed #9532 -- Added min_num and validate_min on formsets.

Thanks gsf for the suggestion.

django/forms/formsets.py

@@ -18,10 +18,14 @@ __all__ = ('BaseFormSet', 'all_valid')
 # special field names
 TOTAL_FORM_COUNT = 'TOTAL_FORMS'
 INITIAL_FORM_COUNT = 'INITIAL_FORMS'
+MIN_NUM_FORM_COUNT = 'MIN_NUM_FORMS'
 MAX_NUM_FORM_COUNT = 'MAX_NUM_FORMS'
 ORDERING_FIELD_NAME = 'ORDER'
 DELETION_FIELD_NAME = 'DELETE'
 
+# default minimum number of forms in a formset
+DEFAULT_MIN_NUM = 0
+
 # default maximum number of forms in a formset, to prevent memory exhaustion
 DEFAULT_MAX_NUM = 1000
 
@@ -34,9 +38,10 @@ class ManagementForm(Form):
     def __init__(self, *args, **kwargs):
         self.base_fields[TOTAL_FORM_COUNT] = IntegerField(widget=HiddenInput)
         self.base_fields[INITIAL_FORM_COUNT] = IntegerField(widget=HiddenInput)
-        # MAX_NUM_FORM_COUNT is output with the rest of the management form,
-        # but only for the convenience of client-side code. The POST
-        # value of MAX_NUM_FORM_COUNT returned from the client is not checked.
+        # MIN_NUM_FORM_COUNT and MAX_NUM_FORM_COUNT are output with the rest of
+        # the management form, but only for the convenience of client-side
+        # code. The POST value of them returned from the client is not checked.
+        self.base_fields[MIN_NUM_FORM_COUNT] = IntegerField(required=False, widget=HiddenInput)
         self.base_fields[MAX_NUM_FORM_COUNT] = IntegerField(required=False, widget=HiddenInput)
         super(ManagementForm, self).__init__(*args, **kwargs)
 
@@ -92,6 +97,7 @@ class BaseFormSet(object):
             form = ManagementForm(auto_id=self.auto_id, prefix=self.prefix, initial={
                 TOTAL_FORM_COUNT: self.total_form_count(),
                 INITIAL_FORM_COUNT: self.initial_form_count(),
+                MIN_NUM_FORM_COUNT: self.min_num,
                 MAX_NUM_FORM_COUNT: self.max_num
             })
         return form
@@ -323,6 +329,12 @@ class BaseFormSet(object):
                     "Please submit %d or fewer forms.", self.max_num) % self.max_num,
                     code='too_many_forms',
                 )
+            if (self.validate_min and
+                self.total_form_count() - len(self.deleted_forms) < self.min_num):
+                raise ValidationError(ungettext(
+                    "Please submit %d or more forms.",
+                    "Please submit %d or more forms.", self.min_num) % self.min_num,
+                    code='too_few_forms')
             # Give self.clean() a chance to do cross-form validation.
             self.clean()
         except ValidationError as e:
@@ -395,17 +407,22 @@ class BaseFormSet(object):
         return mark_safe('\n'.join([six.text_type(self.management_form), forms]))
 
 def formset_factory(form, formset=BaseFormSet, extra=1, can_order=False,
-                    can_delete=False, max_num=None, validate_max=False):
+                    can_delete=False, max_num=None, validate_max=False,
+                    min_num=None, validate_min=False):
     """Return a FormSet for the given form class."""
+    if min_num is None:
+        min_num = DEFAULT_MIN_NUM
     if max_num is None:
         max_num = DEFAULT_MAX_NUM
     # hard limit on forms instantiated, to prevent memory-exhaustion attacks
     # limit is simply max_num + DEFAULT_MAX_NUM (which is 2*DEFAULT_MAX_NUM
     # if max_num is None in the first place)
     absolute_max = max_num + DEFAULT_MAX_NUM
+    extra += min_num
     attrs = {'form': form, 'extra': extra,
              'can_order': can_order, 'can_delete': can_delete,
-             'max_num': max_num, 'absolute_max': absolute_max,
+             'min_num': min_num, 'max_num': max_num,
+             'absolute_max': absolute_max, 'validate_min' : validate_min,
              'validate_max' : validate_max}
     return type(form.__name__ + str('FormSet'), (formset,), attrs)
 

docs/ref/forms/formsets.txt

@@ -5,12 +5,16 @@ Formset Functions
 .. module:: django.forms.formsets
    :synopsis: Django's functions for building formsets.
 
-.. function:: formset_factory(form, formset=BaseFormSet, extra=1, can_order=False, can_delete=False, max_num=None, validate_max=False)
+.. function:: formset_factory(form, formset=BaseFormSet, extra=1, can_order=False, can_delete=False, max_num=None, validate_max=False, min_num=None, validate_min=False)
 
     Returns a ``FormSet`` class for the given ``form`` class.
 
     See :ref:`formsets` for example usage.
 
     .. versionchanged:: 1.6
-    
+
     The ``validate_max`` parameter was added.
+
+    .. versionchanged:: 1.7
+
+    The ``min_num`` and ``validate_min`` parameters were added.

docs/releases/1.7.txt

@@ -234,6 +234,10 @@ Forms
   <django.forms.extras.widgets.SelectDateWidget.months>` can be used to
   customize the wording of the months displayed in the select widget.
 
+* The ``min_num`` and ``validate_min`` parameters were added to
+  :func:`~django.forms.formsets.formset_factory` to allow validating
+  a minimum number of submitted forms.
+
 Management Commands
 ^^^^^^^^^^^^^^^^^^^
 

docs/topics/forms/formsets.txt

@@ -298,6 +298,13 @@ method on the formset.
 Validating the number of forms in a formset
 -------------------------------------------
 
+Django provides a couple ways to validate the minimum or maximum number of
+submitted forms. Applications which need more customizable validation of the
+number of forms should use custom formset validation.
+
+``validate_max``
+~~~~~~~~~~~~~~~~
+
 If ``validate_max=True`` is passed to
 :func:`~django.forms.formsets.formset_factory`, validation will also check
 that the number of forms in the data set, minus those marked for
@@ -309,6 +316,7 @@ deletion, is less than or equal to ``max_num``.
     >>> data = {
     ...     'form-TOTAL_FORMS': u'2',
     ...     'form-INITIAL_FORMS': u'0',
+    ...     'form-MIN_NUM_FORMS': u'',
     ...     'form-MAX_NUM_FORMS': u'',
     ...     'form-0-title': u'Test',
     ...     'form-0-pub_date': u'1904-06-16',
@@ -327,9 +335,6 @@ deletion, is less than or equal to ``max_num``.
 ``max_num`` was exceeded because the amount of initial data supplied was
 excessive.
 
-Applications which need more customizable validation of the number of forms
-should use custom formset validation.
-
 .. note::
 
     Regardless of ``validate_max``, if the number of forms in a data set
@@ -344,6 +349,42 @@ should use custom formset validation.
    The ``validate_max`` parameter was added to
    :func:`~django.forms.formsets.formset_factory`.
 
+``validate_min``
+~~~~~~~~~~~~~~~~
+
+.. versionadded:: 1.7
+
+If ``validate_min=True`` is passed to
+:func:`~django.forms.formsets.formset_factory`, validation will also check
+that the number of forms in the data set, minus those marked for
+deletion, is greater than or equal to ``min_num``.
+
+    >>> from django.forms.formsets import formset_factory
+    >>> from myapp.forms import ArticleForm
+    >>> ArticleFormSet = formset_factory(ArticleForm, min_num=3, validate_min=True)
+    >>> data = {
+    ...     'form-TOTAL_FORMS': u'2',
+    ...     'form-INITIAL_FORMS': u'0',
+    ...     'form-MIN_NUM_FORMS': u'',
+    ...     'form-MAX_NUM_FORMS': u'',
+    ...     'form-0-title': u'Test',
+    ...     'form-0-pub_date': u'1904-06-16',
+    ...     'form-1-title': u'Test 2',
+    ...     'form-1-pub_date': u'1912-06-23',
+    ... }
+    >>> formset = ArticleFormSet(data)
+    >>> formset.is_valid()
+    False
+    >>> formset.errors
+    [{}, {}]
+    >>> formset.non_form_errors()
+    [u'Please submit 3 or more forms.']
+
+.. versionchanged:: 1.7
+
+   The ``min_num`` and ``validate_min`` parameters were added to
+   :func:`~django.forms.formsets.formset_factory`.
+
 Dealing with ordering and deletion of forms
 -------------------------------------------
 

tests/admin_views/tests.py

@@ -1874,14 +1874,14 @@ class AdminViewListEditable(TestCase):
     def test_changelist_input_html(self):
         response = self.client.get('/test_admin/admin/admin_views/person/')
         # 2 inputs per object(the field and the hidden id field) = 6
-        # 3 management hidden fields = 3
+        # 4 management hidden fields = 4
         # 4 action inputs (3 regular checkboxes, 1 checkbox to select all)
         # main form submit button = 1
         # search field and search submit button = 2
         # CSRF field = 1
         # field to track 'select all' across paginated views = 1
-        # 6 + 3 + 4 + 1 + 2 + 1 + 1 = 18 inputs
-        self.assertContains(response, "<input", count=18)
+        # 6 + 4 + 4 + 1 + 2 + 1 + 1 = 19 inputs
+        self.assertContains(response, "<input", count=19)
         # 1 select per object = 3 selects
         self.assertContains(response, "<select", count=4)
 
@@ -3629,9 +3629,9 @@ class ReadonlyTest(TestCase):
         response = self.client.get('/test_admin/admin/admin_views/post/add/')
         self.assertEqual(response.status_code, 200)
         self.assertNotContains(response, 'name="posted"')
-        # 3 fields + 2 submit buttons + 4 inline management form fields, + 2
+        # 3 fields + 2 submit buttons + 5 inline management form fields, + 2
         # hidden fields for inlines + 1 field for the inline + 2 empty form
-        self.assertContains(response, "<input", count=14)
+        self.assertContains(response, "<input", count=15)
         self.assertContains(response, formats.localize(datetime.date.today()))
         self.assertContains(response,
             "<label>Awesomeness level:</label>")