[3.7] bpo-33482: fix codecs.StreamRecoder.writelines (GH-6779) (GH-13502)

A very simple fix. I found this while writing typeshed stubs for StreamRecoder.

https://bugs.python.org/issue33482.
(cherry picked from commit b3be4072888a4ce054993c2801802721466ea02d)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>





https://bugs.python.org/issue33482

2 files changed, 22 insertions, 1 deletions

diff --git a/Lib/codecs.py b/Lib/codecs.py
index a70ed20f2b..3cd78fc9f1 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -838,7 +838,7 @@ class StreamRecoder:
 
     def writelines(self, list):
 
-        data = ''.join(list)
+        data = b''.join(list)
         data, bytesdecoded = self.decode(data, self.errors)
         return self.writer.write(data)
 
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 5ba2c7bdc5..a3a2f6563a 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -3298,5 +3298,26 @@ class Latin1Test(unittest.TestCase):
                 self.assertEqual(data.decode('latin1'), expected)
 
 
+class StreamRecoderTest(unittest.TestCase):
+    def test_writelines(self):
+        bio = io.BytesIO()
+        codec = codecs.lookup('ascii')
+        sr = codecs.StreamRecoder(bio, codec.encode, codec.decode,
+                                  encodings.ascii.StreamReader, encodings.ascii.StreamWriter)
+        sr.writelines([b'a', b'b'])
+        self.assertEqual(bio.getvalue(), b'ab')
+
+    def test_write(self):
+        bio = io.BytesIO()
+        codec = codecs.lookup('latin1')
+        # Recode from Latin-1 to utf-8.
+        sr = codecs.StreamRecoder(bio, codec.encode, codec.decode,
+                                  encodings.utf_8.StreamReader, encodings.utf_8.StreamWriter)
+
+        text = 'àñé'
+        sr.write(text.encode('latin1'))
+        self.assertEqual(bio.getvalue(), text.encode('utf-8'))
+
+
 if __name__ == "__main__":
     unittest.main()