db/message: guess a better content type for octet-stream parts

Same as what is done for Attachment.

1 files changed, 25 insertions, 3 deletions

diff --git a/alot/db/message.py b/alot/db/message.py
index cb72b2ad..a8590d9f 100644
--- a/alot/db/message.py
+++ b/alot/db/message.py
@@ -106,6 +106,12 @@ class _MessageHeaders:
 class _MimeTree:
     _part = None
 
+    # content-type: (maintype, subtype)
+    # may differ from that indicated in _part,
+    # e.g. when it reports octet-stream, but we guess
+    # something more specific
+    _ctype_val = None
+
     is_signed     = False
     is_encrypted  = False
     sig_valid     = None
@@ -181,14 +187,30 @@ class _MimeTree:
         return self._part.as_bytes()
 
     @property
+    def _ctype(self):
+        if self._ctype_val is None:
+            ctype = self._part.get_content_type()
+
+            # replace underspecified mime description by a better guess
+            if ctype in ['octet/stream', 'application/octet-stream',
+                         'application/octetstream']:
+                ctype = helper.guess_mimetype(self._part.get_content())
+                logging.debug('Overriding octet-stream content type to %s', ctype)
+
+            maintype, _, subtype = ctype.partition('/')
+            self._ctype_val = (maintype, subtype)
+
+        return self._ctype_val
+
+    @property
     def content_type(self):
-        return self._part.get_content_type()
+        return '/'.join(self._ctype)
     @property
     def content_maintype(self):
-        return self._part.get_content_maintype()
+        return self._ctype[0]
     @property
     def content_subtype(self):
-        return self._part.get_content_subtype()
+        return self._ctype[1]
 
     @property
     def filename(self):