Fixed model.__eq__ and __hash__ for no pk value cases

The __eq__ method now considers two instances without primary key value
equal only when they have same id(). The __hash__ method raises
TypeError for no primary key case.

Fixed #18864, fixed #18250

Thanks to Tim Graham for docs review.

2 files changed, 15 insertions, 4 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 3e2ae8d425..a5b0f188b4 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -459,14 +459,21 @@ class Model(six.with_metaclass(ModelBase)):
         return '%s object' % self.__class__.__name__
 
     def __eq__(self, other):
-        return (isinstance(other, Model) and
-                self._meta.concrete_model == other._meta.concrete_model and
-                self._get_pk_val() == other._get_pk_val())
+        if not isinstance(other, Model):
+            return False
+        if self._meta.concrete_model != other._meta.concrete_model:
+            return False
+        my_pk = self._get_pk_val()
+        if my_pk is None:
+            return self is other
+        return my_pk == other._get_pk_val()
 
     def __ne__(self, other):
         return not self.__eq__(other)
 
     def __hash__(self):
+        if self._get_pk_val() is None:
+            raise TypeError("Model instances without primary key value are unhashable")
         return hash(self._get_pk_val())
 
     def __reduce__(self):
diff --git a/django/forms/models.py b/django/forms/models.py
index a5b82e521d..4c6ee9c6ed 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -631,7 +631,11 @@ class BaseModelFormSet(BaseFormSet):
             seen_data = set()
             for form in valid_forms:
                 # get data for each field of each of unique_check
-                row_data = tuple([form.cleaned_data[field] for field in unique_check if field in form.cleaned_data])
+                row_data = (form.cleaned_data[field]
+                            for field in unique_check if field in form.cleaned_data)
+                # Reduce Model instances to their primary key values
+                row_data = tuple(d._get_pk_val() if hasattr(d, '_get_pk_val') else d
+                                 for d in row_data)
                 if row_data and not None in row_data:
                     # if we've already seen it then we have a uniqueness failure
                     if row_data in seen_data: