Refs #16508 -- Renamed the current "virtual" fields to "private".

The only reason why GenericForeignKey and GenericRelation are stored
separately inside _meta is that they need to be cloned for every model
subclass, but that's not true for any other virtual field. Actually,
it's only true for GenericRelation.

8 files changed, 63 insertions, 30 deletions

diff --git a/django/contrib/contenttypes/admin.py b/django/contrib/contenttypes/admin.py
index be0ee2dea5..f15f66b2e1 100644
--- a/django/contrib/contenttypes/admin.py
+++ b/django/contrib/contenttypes/admin.py
@@ -24,7 +24,7 @@ class GenericInlineModelAdminChecks(InlineModelAdminChecks):
         # and that they are part of a GenericForeignKey.
 
         gfks = [
-            f for f in obj.model._meta.virtual_fields
+            f for f in obj.model._meta.private_fields
             if isinstance(f, GenericForeignKey)
         ]
         if len(gfks) == 0:
diff --git a/django/contrib/contenttypes/fields.py b/django/contrib/contenttypes/fields.py
index 3ff5ad7f0e..592aee6c9f 100644
--- a/django/contrib/contenttypes/fields.py
+++ b/django/contrib/contenttypes/fields.py
@@ -53,7 +53,7 @@ class GenericForeignKey(object):
         self.name = name
         self.model = cls
         self.cache_attr = "_%s_cache" % name
-        cls._meta.add_field(self, virtual=True)
+        cls._meta.add_field(self, private=True)
 
         # Only run pre-initialization field assignment on non-abstract models
         if not cls._meta.abstract:
@@ -331,7 +331,7 @@ class GenericRelation(ForeignObject):
     def _check_generic_foreign_key_existence(self):
         target = self.remote_field.model
         if isinstance(target, ModelBase):
-            fields = target._meta.virtual_fields
+            fields = target._meta.private_fields
             if any(isinstance(field, GenericForeignKey) and
                     field.ct_field == self.content_type_field_name and
                     field.fk_field == self.object_id_field_name
@@ -409,7 +409,7 @@ class GenericRelation(ForeignObject):
         return smart_text([instance._get_pk_val() for instance in qs])
 
     def contribute_to_class(self, cls, name, **kwargs):
-        kwargs['virtual_only'] = True
+        kwargs['private_only'] = True
         super(GenericRelation, self).contribute_to_class(cls, name, **kwargs)
         self.model = cls
         setattr(cls, self.name, ReverseGenericManyToOneDescriptor(self.remote_field))
diff --git a/django/db/models/base.py b/django/db/models/base.py
index c029fd812a..1c454f9b0a 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -161,7 +161,7 @@ class ModelBase(type):
         new_fields = chain(
             new_class._meta.local_fields,
             new_class._meta.local_many_to_many,
-            new_class._meta.virtual_fields
+            new_class._meta.private_fields
         )
         field_names = {f.name for f in new_fields}
 
@@ -268,9 +268,9 @@ class ModelBase(type):
             if is_proxy:
                 new_class.copy_managers(original_base._meta.concrete_managers)
 
-            # Inherit virtual fields (like GenericForeignKey) from the parent
+            # Inherit private fields (like GenericForeignKey) from the parent
             # class
-            for field in base._meta.virtual_fields:
+            for field in base._meta.private_fields:
                 if base._meta.abstract and field.name in field_names:
                     raise FieldError(
                         'Local field %r in class %r clashes '
diff --git a/django/db/models/deletion.py b/django/db/models/deletion.py
index 07ee0459de..91c1bfa245 100644
--- a/django/db/models/deletion.py
+++ b/django/db/models/deletion.py
@@ -147,7 +147,7 @@ class Collector(object):
         for related in get_candidate_relations_to_delete(opts):
             if related.field.remote_field.on_delete is not DO_NOTHING:
                 return False
-        for field in model._meta.virtual_fields:
+        for field in model._meta.private_fields:
             if hasattr(field, 'bulk_related_objects'):
                 # It's something like generic foreign key.
                 return False
@@ -221,7 +221,7 @@ class Collector(object):
                         self.fast_deletes.append(sub_objs)
                     elif sub_objs:
                         field.remote_field.on_delete(self, field, sub_objs, self.using)
-            for field in model._meta.virtual_fields:
+            for field in model._meta.private_fields:
                 if hasattr(field, 'bulk_related_objects'):
                     # It's something like generic foreign key.
                     sub_objs = field.bulk_related_objects(new_objs, self.using)
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 15f4789bbc..a4018dd6e9 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -672,11 +672,25 @@ class Field(RegisterLookupMixin):
         if self.verbose_name is None and self.name:
             self.verbose_name = self.name.replace('_', ' ')
 
-    def contribute_to_class(self, cls, name, virtual_only=False):
+    def contribute_to_class(self, cls, name, private_only=False, virtual_only=NOT_PROVIDED):
+        """
+        Register the field with the model class it belongs to.
+
+        If private_only is True, a separate instance of this field will be
+        created for every subclass of cls, even if cls is not an abstract
+        model.
+        """
+        if virtual_only is not NOT_PROVIDED:
+            warnings.warn(
+                "The `virtual_only` argument of Field.contribute_to_class() "
+                "has been renamed to `private_only`.",
+                RemovedInDjango20Warning, stacklevel=2
+            )
+            private_only = virtual_only
         self.set_attributes_from_name(name)
         self.model = cls
-        if virtual_only:
-            cls._meta.add_field(self, virtual=True)
+        if private_only:
+            cls._meta.add_field(self, private=True)
         else:
             cls._meta.add_field(self)
         if self.choices:
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 0539647bcc..1bd1248c71 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -282,9 +282,9 @@ class RelatedField(Field):
         # columns from another table.
         return None
 
-    def contribute_to_class(self, cls, name, virtual_only=False):
+    def contribute_to_class(self, cls, name, private_only=False, **kwargs):
 
-        super(RelatedField, self).contribute_to_class(cls, name, virtual_only=virtual_only)
+        super(RelatedField, self).contribute_to_class(cls, name, private_only=private_only, **kwargs)
 
         self.opts = cls._meta
 
@@ -703,8 +703,8 @@ class ForeignObject(RelatedField):
     def get_defaults(self):
         return tuple(field.get_default() for field in self.local_related_fields)
 
-    def contribute_to_class(self, cls, name, virtual_only=False):
-        super(ForeignObject, self).contribute_to_class(cls, name, virtual_only=virtual_only)
+    def contribute_to_class(self, cls, name, private_only=False, **kwargs):
+        super(ForeignObject, self).contribute_to_class(cls, name, private_only=private_only, **kwargs)
         setattr(cls, self.name, ForwardManyToOneDescriptor(self))
 
     def contribute_to_related_class(self, cls, related):
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 0432d6958a..c6ddd2a6f9 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+import warnings
 from bisect import bisect
 from collections import OrderedDict, defaultdict
 from itertools import chain
@@ -12,6 +13,9 @@ from django.db.models.fields import AutoField
 from django.db.models.fields.proxy import OrderWrt
 from django.utils import six
 from django.utils.datastructures import ImmutableList, OrderedSet
+from django.utils.deprecation import (
+    RemovedInDjango20Warning, warn_about_renamed_method,
+)
 from django.utils.encoding import (
     force_text, python_2_unicode_compatible, smart_text,
 )
@@ -19,6 +23,8 @@ from django.utils.functional import cached_property
 from django.utils.text import camel_case_to_spaces
 from django.utils.translation import override, string_concat
 
+NOT_PROVIDED = object()
+
 PROXY_PARENTS = object()
 
 EMPTY_RELATION_TREE = tuple()
@@ -76,7 +82,7 @@ class Options(object):
         self._get_fields_cache = {}
         self.local_fields = []
         self.local_many_to_many = []
-        self.virtual_fields = []
+        self.private_fields = []
         self.model_name = None
         self.verbose_name = None
         self.verbose_name_plural = None
@@ -253,13 +259,19 @@ class Options(object):
                 auto = AutoField(verbose_name='ID', primary_key=True, auto_created=True)
                 model.add_to_class('id', auto)
 
-    def add_field(self, field, virtual=False):
+    def add_field(self, field, private=False, virtual=NOT_PROVIDED):
+        if virtual is not NOT_PROVIDED:
+            warnings.warn(
+                "The `virtual` argument of Options.add_field() has been renamed to `private`.",
+                RemovedInDjango20Warning, stacklevel=2
+            )
+            private = virtual
         # Insert the given field in the order in which it was created, using
         # the "creation_counter" attribute of the field.
         # Move many-to-many related fields from self.fields into
         # self.many_to_many.
-        if virtual:
-            self.virtual_fields.append(field)
+        if private:
+            self.private_fields.append(field)
         elif field.is_relation and field.many_to_many:
             self.local_many_to_many.insert(bisect(self.local_many_to_many, field), field)
         else:
@@ -365,7 +377,7 @@ class Options(object):
         obtaining this field list.
         """
         # For legacy reasons, the fields property should only contain forward
-        # fields that are not virtual or with a m2m cardinality. Therefore we
+        # fields that are not private or with a m2m cardinality. Therefore we
         # pass these three filters as filters to the generator.
         # The third lambda is a longwinded way of checking f.related_model - we don't
         # use that property directly because related_model is a cached property,
@@ -401,6 +413,14 @@ class Options(object):
             "concrete_fields", (f for f in self.fields if f.concrete)
         )
 
+    @property
+    @warn_about_renamed_method(
+        'Options', 'virtual_fields', 'private_fields',
+        RemovedInDjango20Warning
+    )
+    def virtual_fields(self):
+        return self.private_fields
+
     @cached_property
     def local_concrete_fields(self):
         """
@@ -686,14 +706,14 @@ class Options(object):
             fields.extend(
                 field for field in chain(self.local_fields, self.local_many_to_many)
             )
-            # Virtual fields are recopied to each child model, and they get a
+            # Private fields are recopied to each child model, and they get a
             # different model as field.model in each child. Hence we have to
-            # add the virtual fields separately from the topmost call. If we
+            # add the private fields separately from the topmost call. If we
             # did this recursively similar to local_fields, we would get field
             # instances with field.model != self.model.
             if topmost_call:
                 fields.extend(
-                    f for f in self.virtual_fields
+                    f for f in self.private_fields
                 )
 
         # In order to avoid list manipulation. Always
diff --git a/django/forms/models.py b/django/forms/models.py
index 849f7a111a..aac75b54ff 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -81,7 +81,7 @@ def model_to_dict(instance, fields=None, exclude=None):
     """
     opts = instance._meta
     data = {}
-    for f in chain(opts.concrete_fields, opts.virtual_fields, opts.many_to_many):
+    for f in chain(opts.concrete_fields, opts.private_fields, opts.many_to_many):
         if not getattr(f, 'editable', False):
             continue
         if fields and f.name not in fields:
@@ -142,9 +142,8 @@ def fields_for_model(model, fields=None, exclude=None, widgets=None,
     opts = model._meta
     # Avoid circular import
     from django.db.models.fields import Field as ModelField
-    sortable_virtual_fields = [f for f in opts.virtual_fields
-                               if isinstance(f, ModelField)]
-    for f in sorted(chain(opts.concrete_fields, sortable_virtual_fields, opts.many_to_many)):
+    sortable_private_fields = [f for f in opts.private_fields if isinstance(f, ModelField)]
+    for f in sorted(chain(opts.concrete_fields, sortable_private_fields, opts.many_to_many)):
         if not getattr(f, 'editable', False):
             if (fields is not None and f.name in fields and
                     (exclude is None or f.name not in exclude)):
@@ -431,9 +430,9 @@ class BaseModelForm(BaseForm):
         fields = self._meta.fields
         opts = self.instance._meta
         # Note that for historical reasons we want to include also
-        # virtual_fields here. (GenericRelation was previously a fake
+        # private_fields here. (GenericRelation was previously a fake
         # m2m field).
-        for f in chain(opts.many_to_many, opts.virtual_fields):
+        for f in chain(opts.many_to_many, opts.private_fields):
             if not hasattr(f, 'save_form_data'):
                 continue
             if fields and f.name not in fields: