From d5119969012aa69b9b4ef345c7e0beb7d890509d Mon Sep 17 00:00:00 2001
From: Brian Rosner <brosner@gmail.com>
Date: Sun, 31 Aug 2008 21:14:46 +0000
Subject: [PATCH] Enforce max_num=1 on inline model formsets that have a unique
 foreign key to its parent. I snuck in a quick clean up to the
 inlineformset_factory as well.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8775 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/forms/models.py                    | 22 +++++++++++++++-------
 tests/modeltests/model_formsets/models.py | 15 +++++++++++++++
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/django/forms/models.py b/django/forms/models.py
index 6acd32ce4f..4563ace3a2 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -424,17 +424,25 @@ def inlineformset_factory(parent_model, model, form=ModelForm,
     to ``parent_model``.
     """
     fk = _get_foreign_key(parent_model, model, fk_name=fk_name)
-    # let the formset handle object deletion by default
-
+    # enforce a max_num=1 when the foreign key to the parent model is unique.
+    if fk.unique:
+        max_num = 1
     if exclude is not None:
         exclude.append(fk.name)
     else:
         exclude = [fk.name]
-    FormSet = modelformset_factory(model, form=form,
-                                    formfield_callback=formfield_callback,
-                                    formset=formset,
-                                    extra=extra, can_delete=can_delete, can_order=can_order,
-                                    fields=fields, exclude=exclude, max_num=max_num)
+    kwargs = {
+        'form': form,
+        'formfield_callback': formfield_callback,
+        'formset': formset,
+        'extra': extra,
+        'can_delete': can_delete,
+        'can_order': can_order,
+        'fields': fields,
+        'exclude': exclude,
+        'max_num': max_num,
+    }
+    FormSet = modelformset_factory(model, **kwargs)
     FormSet.fk = fk
     return FormSet
 
diff --git a/tests/modeltests/model_formsets/models.py b/tests/modeltests/model_formsets/models.py
index b0ad420003..332c5a7235 100644
--- a/tests/modeltests/model_formsets/models.py
+++ b/tests/modeltests/model_formsets/models.py
@@ -54,6 +54,12 @@ class Owner(models.Model):
     def __unicode__(self):
         return "%s at %s" % (self.name, self.place)
 
+class Location(models.Model):
+    place = models.ForeignKey(Place, unique=True)
+    # this is purely for testing the data doesn't matter here :)
+    lat = models.CharField(max_length=100)
+    lon = models.CharField(max_length=100)
+
 class OwnerProfile(models.Model):
     owner = models.OneToOneField(Owner, primary_key=True)
     age = models.PositiveIntegerField()
@@ -529,6 +535,15 @@ True
 >>> formset.save()
 [<OwnerProfile: Joe Perry is 55>]
 
+# ForeignKey with unique=True should enforce max_num=1 
+
+>>> FormSet = inlineformset_factory(Place, Location, can_delete=False)
+>>> formset = FormSet(instance=place)
+>>> for form in formset.forms:
+...     print form.as_p()
+<p><label for="id_location_set-0-lat">Lat:</label> <input id="id_location_set-0-lat" type="text" name="location_set-0-lat" maxlength="100" /></p>
+<p><label for="id_location_set-0-lon">Lon:</label> <input id="id_location_set-0-lon" type="text" name="location_set-0-lon" maxlength="100" /><input type="hidden" name="location_set-0-id" id="id_location_set-0-id" /></p>
+
 # Foreign keys in parents ########################################
 
 >>> from django.forms.models import _get_foreign_key