message: Extract build_message_send_dict function.

We extract the loop for building message dict in
do_send_messages in a separate function named
build_message_send_dict.

This is a prep commit for moving the code for building
of message dict in check_message.

zerver/lib/actions.py

@@ -1386,28 +1386,8 @@ def do_schedule_messages(messages: Sequence[Mapping[str, Any]]) -> List[int]:
     return [scheduled_message.id for scheduled_message in scheduled_messages]
 
 
-def do_send_messages(messages_maybe_none: Sequence[Optional[MutableMapping[str, Any]]],
+def build_message_send_dict(message_dict: MutableMapping[str, Any],
-                     email_gateway: bool=False,
+                            email_gateway: bool=False) -> MutableMapping[str, Any]:
-                     mark_as_read: Sequence[int]=[]) -> List[int]:
-    """See
-    https://zulip.readthedocs.io/en/latest/subsystems/sending-messages.html
-    for high-level documentation on this subsystem.
-    """
-
-    # Filter out messages which didn't pass internal_prep_message properly
-    messages = [message for message in messages_maybe_none if message is not None]
-
-    # Filter out zephyr mirror anomalies where the message was already sent
-    already_sent_ids: List[int] = []
-    new_messages: List[MutableMapping[str, Any]] = []
-    for message in messages:
-        if isinstance(message['message'], int):
-            already_sent_ids.append(message['message'])
-        else:
-            new_messages.append(message)
-    messages = new_messages
-
-    for message_dict in messages:
     message_dict['stream'] = message_dict.get('stream', None)
     message_dict['local_id'] = message_dict.get('local_id', None)
     message_dict['sender_queue_id'] = message_dict.get('sender_queue_id', None)
@@ -1485,6 +1465,32 @@ def do_send_messages(messages_maybe_none: Sequence[Optional[MutableMapping[str,
     mentioned_bot_user_ids = default_bot_user_ids & mentioned_user_ids
     message_dict['um_eligible_user_ids'] |= mentioned_bot_user_ids
 
+    return message_dict
+
+def do_send_messages(messages_maybe_none: Sequence[Optional[MutableMapping[str, Any]]],
+                     email_gateway: bool=False,
+                     mark_as_read: Sequence[int]=[]) -> List[int]:
+    """See
+    https://zulip.readthedocs.io/en/latest/subsystems/sending-messages.html
+    for high-level documentation on this subsystem.
+    """
+
+    # Filter out messages which didn't pass internal_prep_message properly
+    messages = [message for message in messages_maybe_none if message is not None]
+
+    # Filter out zephyr mirror anomalies where the message was already sent
+    already_sent_ids: List[int] = []
+    new_messages: List[MutableMapping[str, Any]] = []
+    for message in messages:
+        if isinstance(message['message'], int):
+            already_sent_ids.append(message['message'])
+        else:
+            new_messages.append(message)
+    messages = new_messages
+
+    for message_dict in messages:
+        message_dict = build_message_send_dict(message_dict, email_gateway)
+
     # Save the message receipts in the database
     user_message_flags: Dict[int, Dict[int, List[str]]] = defaultdict(dict)
     with transaction.atomic():