Fixes #28184 - Add ability to pass a callable as the storage param to…

… FileField, and add test

Signed-off-by: miigotu <miigotu@gmail.com>

Add a check that the callable FileField storage is an instance of Storage once instantiated, to assure necessary methods are present

django/db/models/fields/files.py

@@ -3,9 +3,10 @@
 
 from django import forms
 from django.core import checks
+from django.core.exceptions import ImproperlyConfigured
 from django.core.files.base import File
 from django.core.files.images import ImageFile
-from django.core.files.storage import default_storage
+from django.core.files.storage import Storage, default_storage
 from django.db.models import signals
 from django.db.models.fields import Field
 from django.utils.translation import gettext_lazy as _
@@ -224,6 +225,15 @@ def __init__(self, verbose_name=None, name=None, upload_to='', storage=None, **k
         self._primary_key_set_explicitly = 'primary_key' in kwargs
 
         self.storage = storage or default_storage
+
+        if callable(self.storage):
+            self.storage = self.storage()
+            if not isinstance(self.storage, Storage):
+                raise ImproperlyConfigured(
+                    "%s.storage must be a subclass/instance of %s.%s"
+                    % (self.__class__.__name__, Storage.__module__, Storage.__name__)
+                )
+
         self.upload_to = upload_to
 
         kwargs.setdefault('max_length', 100)

tests/file_storage/models.py

@@ -23,10 +23,17 @@ def get_valid_name(self, name):
 
 
 class Storage(models.Model):
-    def custom_upload_to(self, filename):
+
+    @staticmethod
+    def callable_temp_storage():
+        return FileSystemStorage(location=temp_storage_location)
+
+    @staticmethod
+    def custom_upload_to(filename):
         return 'foo'
 
-    def random_upload_to(self, filename):
+    @staticmethod
+    def random_upload_to(filename):
         # This returns a different result each time,
         # to make sure it only gets called once.
         return '%s/%s' % (random.randint(100, 999), filename)
@@ -38,6 +45,10 @@ def random_upload_to(self, filename):
         storage=CustomValidNameStorage(location=temp_storage_location),
         upload_to=random_upload_to,
     )
+    callable_storage = models.FileField(
+        storage=callable_temp_storage,
+        upload_to=custom_upload_to,
+    )
     default = models.FileField(storage=temp_storage, upload_to='tests', default='tests/default.txt')
     empty = models.FileField(storage=temp_storage)
     limited_length = models.FileField(storage=temp_storage, upload_to='tests', max_length=20)

tests/file_storage/tests.py

@@ -10,12 +10,15 @@
 from urllib.request import urlopen
 
 from django.core.cache import cache
-from django.core.exceptions import SuspiciousFileOperation
+from django.core.exceptions import (
+    ImproperlyConfigured, SuspiciousFileOperation,
+)
 from django.core.files.base import ContentFile, File
 from django.core.files.storage import FileSystemStorage, get_storage_class
 from django.core.files.uploadedfile import (
     InMemoryUploadedFile, SimpleUploadedFile, TemporaryUploadedFile,
 )
+from django.db.models import FileField
 from django.db.models.fields.files import FileDescriptor
 from django.test import (
     LiveServerTestCase, SimpleTestCase, TestCase, override_settings,
@@ -801,6 +804,32 @@ def test_stringio(self):
         with temp_storage.open('tests/stringio') as f:
             self.assertEqual(f.read(), b'content')
 
+    def test_callable_base_class_error_raises(self):
+        class NotStorage:
+            pass
+        msg = "FileField.storage must be a subclass/instance of django.core.files.storage.Storage"
+        with self.assertRaisesMessage(ImproperlyConfigured, msg):
+            FileField(storage=NotStorage)
+
+    def test_callable_function_storage_file_field(self):
+        storage = FileSystemStorage(location=temp_storage_location)
+
+        def get_storage():
+            return storage
+
+        obj = FileField(storage=get_storage)
+        self.assertEqual(obj.storage, storage)
+        self.assertEqual(obj.storage.location, storage.location)
+
+    def test_callable_class_storage_file_field(self):
+        class GetStorage(FileSystemStorage):
+            def __init__(self):
+                super(FileSystemStorage, self).__init__(location=temp_storage_location)
+
+        obj = FileField(storage=GetStorage)
+        self.assertIsInstance(obj.storage, Storage)
+        self.assertEqual(obj.storage.location, temp_storage_location)
+
 
 # Tests for a race condition on file saving (#4948).
 # This is written in such a way that it'll always pass on platforms