Fixed #27777 -- Made File.open() work with the with statement (#8310)

Fixed #27777 -- Made File.open() work with the with statement

tests/files/tests.py

@@ -10,7 +10,9 @@ from django.core.files import File
 from django.core.files.base import ContentFile
 from django.core.files.move import file_move_safe
 from django.core.files.temp import NamedTemporaryFile
-from django.core.files.uploadedfile import SimpleUploadedFile, UploadedFile
+from django.core.files.uploadedfile import (
+    InMemoryUploadedFile, SimpleUploadedFile, UploadedFile,
+)
 
 try:
     from PIL import Image
@@ -38,6 +40,23 @@ class FileTests(unittest.TestCase):
         self.assertTrue(f.closed)
         self.assertTrue(orig_file.closed)
 
+    def test_open_resets_opened_file_to_start_and_returns_context_manager(self):
+        file = File(BytesIO(b'content'))
+        file.read()
+        with file.open() as f:
+            self.assertEqual(f.read(), b'content')
+
+    def test_open_reopens_closed_file_and_returns_context_manager(self):
+        temporary_file = tempfile.NamedTemporaryFile(delete=False)
+        file = File(temporary_file)
+        try:
+            file.close()
+            with file.open() as f:
+                self.assertFalse(f.closed)
+        finally:
+            # remove temporary file
+            os.unlink(file.name)
+
     def test_namedtemporaryfile_closes(self):
         """
         The symbol django.core.files.NamedTemporaryFile is assigned as
@@ -178,6 +197,21 @@ class ContentFileTestCase(unittest.TestCase):
         self.assertIsInstance(ContentFile(b"content").read(), bytes)
         self.assertIsInstance(ContentFile("español").read(), str)
 
+    def test_open_resets_file_to_start_and_returns_context_manager(self):
+        file = ContentFile(b'content')
+        with file.open() as f:
+            self.assertEqual(f.read(), b'content')
+        with file.open() as f:
+            self.assertEqual(f.read(), b'content')
+
+
+class InMemoryUploadedFileTests(unittest.TestCase):
+    def test_open_resets_file_to_start_and_returns_context_manager(self):
+        uf = InMemoryUploadedFile(StringIO('1'), '', 'test', 'text/plain', 1, 'utf8')
+        uf.read()
+        with uf.open() as f:
+            self.assertEqual(f.read(), '1')
+
 
 class DimensionClosingBug(unittest.TestCase):
     """