#18324: set_payload now correctly handles binary input.

This also backs out the previous fixes for for #14360, #1717, and #16564.
Those bugs were actually caused by the fact that set_payload didn't decode to
str, thus rendering the model inconsistent.  This fix does mean the data
processed by the encoder functions goes through an extra encode/decode cycle,
but it means the model is always consistent.  Future API updates will provide
a better way to encode payloads, which will bypass this minor de-optimization.

Tests by Vajrasky Kok.

2 files changed, 6 insertions, 16 deletions

diff --git a/Lib/email/encoders.py b/Lib/email/encoders.py
index a0d062a..f9657f0 100644
--- a/Lib/email/encoders.py
+++ b/Lib/email/encoders.py
@@ -28,7 +28,7 @@ def encode_base64(msg):
 
     Also, add an appropriate Content-Transfer-Encoding header.
     """
-    orig = msg.get_payload()
+    orig = msg.get_payload(decode=True)
     encdata = str(_bencode(orig), 'ascii')
     msg.set_payload(encdata)
     msg['Content-Transfer-Encoding'] = 'base64'
@@ -40,20 +40,16 @@ def encode_quopri(msg):
 
     Also, add an appropriate Content-Transfer-Encoding header.
     """
-    orig = msg.get_payload()
-    if isinstance(orig, str):
-        # If it is a string, the model data may have binary data encoded in via
-        # surrogateescape.  Convert back to bytes so we can CTE encode it.
-        orig = orig.encode('ascii', 'surrogateescape')
+    orig = msg.get_payload(decode=True)
     encdata = _qencode(orig)
-    msg.set_payload(encdata.decode('ascii', 'surrogateescape'))
+    msg.set_payload(encdata)
     msg['Content-Transfer-Encoding'] = 'quoted-printable'
 
 
 
 def encode_7or8bit(msg):
     """Set the Content-Transfer-Encoding header to 7bit or 8bit."""
-    orig = msg.get_payload()
+    orig = msg.get_payload(decode=True)
     if orig is None:
         # There's no payload.  For backwards compatibility we use 7bit
         msg['Content-Transfer-Encoding'] = '7bit'
@@ -75,16 +71,8 @@ def encode_7or8bit(msg):
             msg['Content-Transfer-Encoding'] = '8bit'
     else:
         msg['Content-Transfer-Encoding'] = '7bit'
-    if not isinstance(orig, str):
-        msg.set_payload(orig.decode('ascii', 'surrogateescape'))
 
 
 
 def encode_noop(msg):
     """Do nothing."""
-    # Well, not quite *nothing*: in Python3 we have to turn bytes into a string
-    # in our internal surrogateescaped form in order to keep the model
-    # consistent.
-    orig = msg.get_payload()
-    if not isinstance(orig, str):
-        msg.set_payload(orig.decode('ascii', 'surrogateescape'))
diff --git a/Lib/email/message.py b/Lib/email/message.py
index 3feab52..5020a03 100644
--- a/Lib/email/message.py
+++ b/Lib/email/message.py
@@ -275,6 +275,8 @@ class Message:
         Optional charset sets the message's default character set.  See
         set_charset() for details.
         """
+        if isinstance(payload, bytes):
+            payload = payload.decode('ascii', 'surrogateescape')
         self._payload = payload
         if charset is not None:
             self.set_charset(charset)