[s3] S3Boto3StorageFile respects mode on readlines (#1000)

storages/backends/s3boto3.py

@@ -167,6 +167,9 @@ def readline(self, *args, **kwargs):
             raise AttributeError("File was not opened in read mode.")
         return self._force_mode(super().readline(*args, **kwargs))
 
+    def readlines(self):
+        return list(self)
+
     def write(self, content):
         if 'w' not in self._mode:
             raise AttributeError("File was not opened in write mode.")

tests/test_s3boto3.py

@@ -1,5 +1,6 @@
 import datetime
 import gzip
+import io
 import pickle
 import threading
 from textwrap import dedent
@@ -300,6 +301,25 @@ def test_storage_open_read_string(self):
         self.assertEqual(content_str, "")
         file.close()
 
+    def test_storage_open_readlines(self):
+        """
+        Test readlines with file opened in "r" and "rb" modes
+        """
+        name = 'test_open_readlines_string.txt'
+        with io.BytesIO() as temp_file:
+            temp_file.write(b"line1\nline2")
+            file = self.storage.open(name, "r")
+            file._file = temp_file
+
+            content_lines = file.readlines()
+            self.assertEqual(content_lines, ["line1\n", "line2"])
+
+            temp_file.seek(0)
+            file = self.storage.open(name, "rb")
+            file._file = temp_file
+            content_lines = file.readlines()
+            self.assertEqual(content_lines, [b"line1\n", b"line2"])
+
     def test_storage_open_write(self):
         """
         Test opening a file in write mode