From 93ffa81bc59ff13c1a5c07f5bd22d003756e1da5 Mon Sep 17 00:00:00 2001
From: Jon Dufresne <jon.dufresne@gmail.com>
Date: Tue, 23 Jul 2019 05:04:06 -0700
Subject: [PATCH] Refs #30657 -- Made DeferredAttribute.__init__() to take a
 field instance instead of a field name.

---
 django/contrib/gis/db/models/proxy.py | 13 ++++++-------
 django/db/models/fields/__init__.py   |  2 +-
 django/db/models/query_utils.py       | 24 ++++++++++++------------
 3 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/django/contrib/gis/db/models/proxy.py b/django/contrib/gis/db/models/proxy.py
index 282109b7254..adf2bae1e5b 100644
--- a/django/contrib/gis/db/models/proxy.py
+++ b/django/contrib/gis/db/models/proxy.py
@@ -14,10 +14,9 @@ class SpatialProxy(DeferredAttribute):
         Initialize on the given Geometry or Raster class (not an instance)
         and the corresponding field.
         """
-        self._field = field
         self._klass = klass
         self._load_func = load_func or klass
-        super().__init__(field.attname)
+        super().__init__(field)
 
     def __get__(self, instance, cls=None):
         """
@@ -32,7 +31,7 @@ class SpatialProxy(DeferredAttribute):
 
         # Getting the value of the field.
         try:
-            geo_value = instance.__dict__[self._field.attname]
+            geo_value = instance.__dict__[self.field.attname]
         except KeyError:
             geo_value = super().__get__(instance, cls)
 
@@ -44,7 +43,7 @@ class SpatialProxy(DeferredAttribute):
             # Otherwise, a geometry or raster object is built using the field's
             # contents, and the model's corresponding attribute is set.
             geo_obj = self._load_func(geo_value)
-            setattr(instance, self._field.attname, geo_obj)
+            setattr(instance, self.field.attname, geo_obj)
         return geo_obj
 
     def __set__(self, instance, value):
@@ -56,7 +55,7 @@ class SpatialProxy(DeferredAttribute):
         To set rasters, use JSON or dict values.
         """
         # The geographic type of the field.
-        gtype = self._field.geom_type
+        gtype = self.field.geom_type
 
         if gtype == 'RASTER' and (value is None or isinstance(value, (str, dict, self._klass))):
             # For raster fields, assure input is None or a string, dict, or
@@ -67,7 +66,7 @@ class SpatialProxy(DeferredAttribute):
             # general GeometryField is used.
             if value.srid is None:
                 # Assigning the field SRID if the geometry has no SRID.
-                value.srid = self._field.srid
+                value.srid = self.field.srid
         elif value is None or isinstance(value, (str, memoryview)):
             # Set geometries with None, WKT, HEX, or WKB
             pass
@@ -76,5 +75,5 @@ class SpatialProxy(DeferredAttribute):
                 instance.__class__.__name__, gtype, type(value)))
 
         # Setting the objects dictionary with the value, and returning.
-        instance.__dict__[self._field.attname] = value
+        instance.__dict__[self.field.attname] = value
         return value
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 6bd8f41a856..a16713a3978 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -738,7 +738,7 @@ class Field(RegisterLookupMixin):
             # if you have a classmethod and a field with the same name, then
             # such fields can't be deferred (we don't have a check for this).
             if not getattr(cls, self.attname, None):
-                setattr(cls, self.attname, DeferredAttribute(self.attname))
+                setattr(cls, self.attname, DeferredAttribute(self))
         if self.choices is not None:
             setattr(cls, 'get_%s_display' % self.name,
                     partialmethod(cls._get_FIELD_display, field=self))
diff --git a/django/db/models/query_utils.py b/django/db/models/query_utils.py
index 90289d0da23..7a667814f43 100644
--- a/django/db/models/query_utils.py
+++ b/django/db/models/query_utils.py
@@ -116,8 +116,8 @@ class DeferredAttribute:
     A wrapper for a deferred-loading field. When the value is read from this
     object the first time, the query is executed.
     """
-    def __init__(self, field_name):
-        self.field_name = field_name
+    def __init__(self, field):
+        self.field = field
 
     def __get__(self, instance, cls=None):
         """
@@ -127,26 +127,26 @@ class DeferredAttribute:
         if instance is None:
             return self
         data = instance.__dict__
-        if data.get(self.field_name, self) is self:
+        field_name = self.field.attname
+        if data.get(field_name, self) is self:
             # Let's see if the field is part of the parent chain. If so we
             # might be able to reuse the already loaded value. Refs #18343.
-            val = self._check_parent_chain(instance, self.field_name)
+            val = self._check_parent_chain(instance)
             if val is None:
-                instance.refresh_from_db(fields=[self.field_name])
-                val = getattr(instance, self.field_name)
-            data[self.field_name] = val
-        return data[self.field_name]
+                instance.refresh_from_db(fields=[field_name])
+                val = getattr(instance, field_name)
+            data[field_name] = val
+        return data[field_name]
 
-    def _check_parent_chain(self, instance, name):
+    def _check_parent_chain(self, instance):
         """
         Check if the field value can be fetched from a parent field already
         loaded in the instance. This can be done if the to-be fetched
         field is a primary key field.
         """
         opts = instance._meta
-        f = opts.get_field(name)
-        link_field = opts.get_ancestor_link(f.model)
-        if f.primary_key and f != link_field:
+        link_field = opts.get_ancestor_link(self.field.model)
+        if self.field.primary_key and self.field != link_field:
             return getattr(instance, link_field.attname)
         return None