Fixed #14549 - Removed restriction of single FKs on intermediary tables

Thanks to Loic Bistuer for review. Minor changes to error messages
done by committer.

2 files changed, 64 insertions, 1 deletions

diff --git a/tests/m2m_through/models.py b/tests/m2m_through/models.py
index 70d6baeca8..aaee0aea3b 100644
--- a/tests/m2m_through/models.py
+++ b/tests/m2m_through/models.py
@@ -77,3 +77,39 @@ class Friendship(models.Model):
     first = models.ForeignKey(PersonSelfRefM2M, related_name="rel_from_set")
     second = models.ForeignKey(PersonSelfRefM2M, related_name="rel_to_set")
     date_friended = models.DateTimeField()
+
+
+# Custom through link fields
+@python_2_unicode_compatible
+class Event(models.Model):
+    title = models.CharField(max_length=50)
+    invitees = models.ManyToManyField(Person, through='Invitation', through_fields=('event', 'invitee'), related_name='events_invited')
+
+    def __str__(self):
+        return self.title
+
+
+class Invitation(models.Model):
+    event = models.ForeignKey(Event, related_name='invitations')
+    # field order is deliberately inverted. the target field is "invitee".
+    inviter = models.ForeignKey(Person, related_name='invitations_sent')
+    invitee = models.ForeignKey(Person, related_name='invitations')
+
+
+@python_2_unicode_compatible
+class Employee(models.Model):
+    name = models.CharField(max_length=5)
+    subordinates = models.ManyToManyField('self', through="Relationship", through_fields=('source', 'target'), symmetrical=False)
+
+    class Meta:
+        ordering = ('pk',)
+
+    def __str__(self):
+        return self.name
+
+
+class Relationship(models.Model):
+    # field order is deliberately inverted.
+    another = models.ForeignKey(Employee, related_name="rel_another_set", null=True)
+    target = models.ForeignKey(Employee, related_name="rel_target_set")
+    source = models.ForeignKey(Employee, related_name="rel_source_set")
diff --git a/tests/m2m_through/tests.py b/tests/m2m_through/tests.py
index 0fa3d4aa55..39621bf958 100644
--- a/tests/m2m_through/tests.py
+++ b/tests/m2m_through/tests.py
@@ -6,7 +6,7 @@ from operator import attrgetter
 from django.test import TestCase
 
 from .models import (Person, Group, Membership, CustomMembership,
-    PersonSelfRefM2M, Friendship)
+    PersonSelfRefM2M, Friendship, Event, Invitation, Employee, Relationship)
 
 
 class M2mThroughTests(TestCase):
@@ -276,6 +276,33 @@ class M2mThroughTests(TestCase):
             attrgetter("name")
         )
 
+    def test_through_fields(self):
+        """
+        Tests that relations with intermediary tables with multiple FKs
+        to the M2M's ``to`` model are possible.
+        """
+        event = Event.objects.create(title='Rockwhale 2014')
+        Invitation.objects.create(event=event, inviter=self.bob, invitee=self.jim)
+        Invitation.objects.create(event=event, inviter=self.bob, invitee=self.jane)
+        self.assertQuerysetEqual(event.invitees.all(), [
+            'Jane',
+            'Jim',
+        ], attrgetter('name'))
+
+    def test_through_fields_self_referential(self):
+        john = Employee.objects.create(name='john')
+        peter = Employee.objects.create(name='peter')
+        mary = Employee.objects.create(name='mary')
+        harry = Employee.objects.create(name='harry')
+        Relationship.objects.create(source=john, target=peter, another=None)
+        Relationship.objects.create(source=john, target=mary, another=None)
+        Relationship.objects.create(source=john, target=harry, another=peter)
+        self.assertQuerysetEqual(john.subordinates.all(), [
+            'peter',
+            'mary',
+            'harry',
+        ], attrgetter('name'))
+
     def test_query_tests(self):
         Membership.objects.create(person=self.jim, group=self.rock)
         m2 = Membership.objects.create(person=self.jane, group=self.rock)