Lowercase usernames before adding them to the database

telethon/tl/session.py

@@ -330,7 +330,7 @@ class Session:
                     p_hash = p.access_hash
 
                 if p_hash is not None:
-                    username = getattr(e, 'username', None)
+                    username = getattr(e, 'username', '').lower() or None
                     phone = getattr(e, 'phone', None)
                     name = utils.get_display_name(e) or None
                     rows.append((marked_id, p_hash, username, phone, name))
@@ -357,6 +357,11 @@ class Session:
            Raises ValueError if it cannot be found.
         """
         c = self._conn.cursor()
+        if isinstance(key, TLObject):
+            if type(key).SUBCLASS_OF_ID == 0xc91c90b6:  # crc32(b'InputPeer')
+                return key
+            key = utils.get_peer_id(key, add_mark=True)
+
         if isinstance(key, str):
             phone = utils.parse_phone(key)
             if phone:
@@ -367,12 +372,6 @@ class Session:
                 c.execute('select id, hash from entities where username=?',
                           (username,))
 
-        if isinstance(key, TLObject):
-            # crc32(b'InputPeer') and crc32(b'Peer')
-            if type(key).SUBCLASS_OF_ID == 0xc91c90b6:
-                return key
-            key = utils.get_peer_id(key, add_mark=True)
-
         if isinstance(key, int):
             c.execute('select id, hash from entities where id=?', (key,))
 

telethon/utils.py

@@ -325,14 +325,17 @@ def parse_phone(phone):
 def parse_username(username):
     """Parses the given username or channel access hash, given
        a string, username or URL. Returns a tuple consisting of
-       both the stripped username and whether it is a joinchat/ hash.
+       both the stripped, lowercase username and whether it is
+       a joinchat/ hash (in which case is not lowercase'd).
     """
     username = username.strip()
     m = USERNAME_RE.match(username)
     if m:
-        return username[m.end():], bool(m.group(1))
+        result = username[m.end():]
+        is_invite = bool(m.group(1))
+        return result if is_invite else result.lower(), is_invite
     else:
-        return username, False
+        return username.lower(), False
 
 
 def get_peer_id(peer, add_mark=False):