Fixed #16470 -- Allowed FileResponse to auto-set some Content headers.

Thanks Simon Charette, Jon Dufresne, and Tim Graham for the reviews.

tests/responses/test_fileresponse.py

@@ -0,0 +1,73 @@
+import io
+import os
+import sys
+import tempfile
+from unittest import skipIf
+
+from django.core.files.base import ContentFile
+from django.http import FileResponse
+from django.test import SimpleTestCase
+
+
+class FileResponseTests(SimpleTestCase):
+    def test_file_from_disk_response(self):
+        response = FileResponse(open(__file__, 'rb'))
+        self.assertEqual(response['Content-Length'], str(os.path.getsize(__file__)))
+        self.assertIn(response['Content-Type'], ['text/x-python', 'text/plain'])
+        response.close()
+
+    def test_file_from_buffer_response(self):
+        response = FileResponse(io.BytesIO(b'binary content'))
+        self.assertEqual(response['Content-Length'], '14')
+        self.assertEqual(response['Content-Type'], 'application/octet-stream')
+        self.assertEqual(list(response), [b'binary content'])
+
+    @skipIf(sys.platform == 'win32', "Named pipes are Unix-only.")
+    def test_file_from_named_pipe_response(self):
+        with tempfile.TemporaryDirectory() as temp_dir:
+            pipe_file = os.path.join(temp_dir, 'named_pipe')
+            os.mkfifo(pipe_file)
+            pipe_for_read = os.open(pipe_file, os.O_RDONLY | os.O_NONBLOCK)
+            with open(pipe_file, 'wb') as pipe_for_write:
+                pipe_for_write.write(b'binary content')
+
+            response = FileResponse(os.fdopen(pipe_for_read, mode='rb'))
+            self.assertEqual(list(response), [b'binary content'])
+            response.close()
+            self.assertFalse(response.has_header('Ĉontent-Length'))
+
+    def test_file_from_disk_as_attachment(self):
+        response = FileResponse(open(__file__, 'rb'), as_attachment=True)
+        self.assertEqual(response['Content-Length'], str(os.path.getsize(__file__)))
+        self.assertIn(response['Content-Type'], ['text/x-python', 'text/plain'])
+        self.assertEqual(response['Content-Disposition'], 'attachment; filename="test_fileresponse.py"')
+        response.close()
+
+    def test_compressed_response(self):
+        """
+        If compressed responses are served with the uncompressed Content-Type
+        and a compression Content-Encoding, browsers might automatically
+        uncompress the file, which is most probably not wanted.
+        """
+        test_tuples = (
+            ('.tar.gz', 'application/gzip'),
+            ('.tar.bz2', 'application/x-bzip'),
+            ('.tar.xz', 'application/x-xz'),
+        )
+        for extension, mimetype in test_tuples:
+            with self.subTest(ext=extension):
+                with tempfile.NamedTemporaryFile(suffix=extension) as tmp:
+                    response = FileResponse(tmp)
+                self.assertEqual(response['Content-Type'], mimetype)
+                self.assertFalse(response.has_header('Content-Encoding'))
+
+    def test_unicode_attachment(self):
+        response = FileResponse(
+            ContentFile(b'binary content', name="祝您平安.odt"), as_attachment=True,
+            content_type='application/vnd.oasis.opendocument.text',
+        )
+        self.assertEqual(response['Content-Type'], 'application/vnd.oasis.opendocument.text')
+        self.assertEqual(
+            response['Content-Disposition'],
+            "attachment; filename*=utf-8''%E7%A5%9D%E6%82%A8%E5%B9%B3%E5%AE%89.odt"
+        )