Fixed #20348 -- Consistently handle Promise objects in model fields.

All Promise objects were passed to force_text() deep in ORM query code.
Not only does this make it difficult or impossible for developers to
prevent or alter this behaviour, but it is also wrong for non-text
fields.

This commit changes `Field.get_prep_value()` from a no-op to one that
resolved Promise objects. All subclasses now call super() method first
to ensure that they have a real value to work with.

4 files changed, 17 insertions, 13 deletions

diff --git a/django/contrib/gis/db/models/fields.py b/django/contrib/gis/db/models/fields.py
index 2e221b7477..d29705986f 100644
--- a/django/contrib/gis/db/models/fields.py
+++ b/django/contrib/gis/db/models/fields.py
@@ -148,6 +148,7 @@ class GeometryField(Field):
         value properly, and preserve any other lookup parameters before
         returning to the caller.
         """
+        value = super(GeometryField, self).get_prep_value(value)
         if isinstance(value, SQLEvaluator):
             return value
         elif isinstance(value, (tuple, list)):
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 4f5707952e..d0a2defc48 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -17,7 +17,7 @@ from django import forms
 from django.core import exceptions, validators
 from django.utils.datastructures import DictWrapper
 from django.utils.dateparse import parse_date, parse_datetime, parse_time
-from django.utils.functional import curry, total_ordering
+from django.utils.functional import curry, total_ordering, Promise
 from django.utils.text import capfirst
 from django.utils import timezone
 from django.utils.translation import ugettext_lazy as _
@@ -421,6 +421,8 @@ class Field(object):
         """
         Perform preliminary non-db specific value checks and conversions.
         """
+        if isinstance(value, Promise):
+            value = value._proxy____cast()
         return value
 
     def get_db_prep_value(self, value, connection, prepared=False):
@@ -704,6 +706,7 @@ class AutoField(Field):
         return value
 
     def get_prep_value(self, value):
+        value = super(AutoField, self).get_prep_value(value)
         if value is None:
             return None
         return int(value)
@@ -763,6 +766,7 @@ class BooleanField(Field):
         return super(BooleanField, self).get_prep_lookup(lookup_type, value)
 
     def get_prep_value(self, value):
+        value = super(BooleanField, self).get_prep_value(value)
         if value is None:
             return None
         return bool(value)
@@ -796,6 +800,7 @@ class CharField(Field):
         return smart_text(value)
 
     def get_prep_value(self, value):
+        value = super(CharField, self).get_prep_value(value)
         return self.to_python(value)
 
     def formfield(self, **kwargs):
@@ -911,6 +916,7 @@ class DateField(Field):
         return super(DateField, self).get_prep_lookup(lookup_type, value)
 
     def get_prep_value(self, value):
+        value = super(DateField, self).get_prep_value(value)
         return self.to_python(value)
 
     def get_db_prep_value(self, value, connection, prepared=False):
@@ -1008,6 +1014,7 @@ class DateTimeField(DateField):
     # get_prep_lookup is inherited from DateField
 
     def get_prep_value(self, value):
+        value = super(DateTimeField, self).get_prep_value(value)
         value = self.to_python(value)
         if value is not None and settings.USE_TZ and timezone.is_naive(value):
             # For backwards compatibility, interpret naive datetimes in local
@@ -1096,6 +1103,7 @@ class DecimalField(Field):
                 self.max_digits, self.decimal_places)
 
     def get_prep_value(self, value):
+        value = super(DecimalField, self).get_prep_value(value)
         return self.to_python(value)
 
     def formfield(self, **kwargs):
@@ -1185,6 +1193,7 @@ class FloatField(Field):
     description = _("Floating point number")
 
     def get_prep_value(self, value):
+        value = super(FloatField, self).get_prep_value(value)
         if value is None:
             return None
         return float(value)
@@ -1218,6 +1227,7 @@ class IntegerField(Field):
     description = _("Integer")
 
     def get_prep_value(self, value):
+        value = super(IntegerField, self).get_prep_value(value)
         if value is None:
             return None
         return int(value)
@@ -1326,6 +1336,7 @@ class GenericIPAddressField(Field):
         return value or None
 
     def get_prep_value(self, value):
+        value = super(GenericIPAddressField, self).get_prep_value(value)
         if value and ':' in value:
             try:
                 return clean_ipv6_address(value, self.unpack_ipv4)
@@ -1391,6 +1402,7 @@ class NullBooleanField(Field):
                                                              value)
 
     def get_prep_value(self, value):
+        value = super(NullBooleanField, self).get_prep_value(value)
         if value is None:
             return None
         return bool(value)
@@ -1473,6 +1485,7 @@ class TextField(Field):
         return "TextField"
 
     def get_prep_value(self, value):
+        value = super(TextField, self).get_prep_value(value)
         if isinstance(value, six.string_types) or value is None:
             return value
         return smart_text(value)
@@ -1549,6 +1562,7 @@ class TimeField(Field):
             return super(TimeField, self).pre_save(model_instance, add)
 
     def get_prep_value(self, value):
+        value = super(TimeField, self).get_prep_value(value)
         return self.to_python(value)
 
     def get_db_prep_value(self, value, connection, prepared=False):
diff --git a/django/db/models/fields/files.py b/django/db/models/fields/files.py
index 311f74a905..61e3eebf49 100644
--- a/django/db/models/fields/files.py
+++ b/django/db/models/fields/files.py
@@ -253,6 +253,7 @@ class FileField(Field):
 
     def get_prep_value(self, value):
         "Returns field's value prepared for saving into a database."
+        value = super(FileField, self).get_prep_value(value)
         # Need to convert File objects provided via a form to unicode for database insertion
         if value is None:
             return None
diff --git a/django/db/models/sql/subqueries.py b/django/db/models/sql/subqueries.py
index 6aab02bd9a..8beb3fa74a 100644
--- a/django/db/models/sql/subqueries.py
+++ b/django/db/models/sql/subqueries.py
@@ -11,8 +11,6 @@ from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, SelectInfo
 from django.db.models.sql.datastructures import Date, DateTime
 from django.db.models.sql.query import Query
 from django.db.models.sql.where import AND, Constraint
-from django.utils.functional import Promise
-from django.utils.encoding import force_text
 from django.utils import six
 from django.utils import timezone
 
@@ -147,10 +145,6 @@ class UpdateQuery(Query):
         Used by add_update_values() as well as the "fast" update path when
         saving models.
         """
-        # Check that no Promise object passes to the query. Refs #10498.
-        values_seq = [(value[0], value[1], force_text(value[2]))
-                      if isinstance(value[2], Promise) else value
-                      for value in values_seq]
         self.values.extend(values_seq)
 
     def add_related_update(self, model, field, value):
@@ -210,12 +204,6 @@ class InsertQuery(Query):
         into the query, for example.
         """
         self.fields = fields
-        # Check that no Promise object reaches the DB. Refs #10498.
-        for field in fields:
-            for obj in objs:
-                value = getattr(obj, field.attname)
-                if isinstance(value, Promise):
-                    setattr(obj, field.attname, force_text(value))
         self.objs = objs
         self.raw = raw