#11684: Complete parser bytes interface by adding BytesHeaderParser

Patch by Steffen Daode Nurpmeso.

Lib/email/generator.py

@@ -297,10 +297,12 @@ class Generator:
         # message/rfc822.  Such messages are generated by, for example,
         # Groupwise when forwarding unadorned messages.  (Issue 7970.)  So
         # in that case we just emit the string body.
-        payload = msg.get_payload()
+        payload = msg._payload
         if isinstance(payload, list):
             g.flatten(msg.get_payload(0), unixfrom=False, linesep=self._NL)
             payload = s.getvalue()
+        else:
+            payload = self._encode(payload)
         self._fp.write(payload)
 
     # This used to be a module level function; we use a classmethod for this

Lib/email/parser.py

@@ -4,7 +4,7 @@
 
 """A parser of RFC 2822 and MIME email messages."""
 
-__all__ = ['Parser', 'HeaderParser']
+__all__ = ['Parser', 'HeaderParser', 'BytesParser', 'BytesHeaderParser']
 
 import warnings
 from io import StringIO, TextIOWrapper
@@ -114,3 +114,11 @@ class BytesParser:
         """
         text = text.decode('ASCII', errors='surrogateescape')
         return self.parser.parsestr(text, headersonly)
+
+
+class BytesHeaderParser(BytesParser):
+    def parse(self, fp, headersonly=True):
+        return BytesParser.parse(self, fp, headersonly=True)
+
+    def parsebytes(self, text, headersonly=True):
+        return BytesParser.parsebytes(self, text, headersonly=True)