Use _force_byte helper

src/paho/mqtt/client.py

@@ -355,6 +355,30 @@ def _socketpair_compat() -> tuple[socket.socket, socket.socket]:
     return (sock1, sock2)
 
 
+def _force_bytes(s: str | bytes) -> bytes:
+    if isinstance(s, str):
+        return s.encode("utf-8")
+    return s
+
+
+def _encode_payload(payload: str | bytes | bytearray | int | float | None) -> bytes:
+    if isinstance(payload, str):
+        return payload.encode("utf-8")
+
+    if isinstance(payload, (int, float)):
+        return str(payload).encode("ascii")
+
+    if payload is None:
+        return b""
+
+    if not isinstance(payload, (bytes, bytearray)):
+        raise TypeError(
+            "payload must be a string, bytearray, int, float or None."
+        )
+
+    return payload
+
+
 class MQTTMessageInfo:
     """This is a class returned from Client.publish() and can be used to find
     out the mid of the message that was published, and to determine whether the
@@ -635,10 +659,7 @@ def __init__(
             else:
                 self._client_id = b""
         else:
-            if isinstance(client_id, str):
-                self._client_id = client_id.encode("utf-8")
-            else:
-                self._client_id = client_id
+            self._client_id = _force_bytes(client_id)
 
         self._username: bytes | None = None
         self._password: bytes | None = None
@@ -1349,17 +1370,7 @@ def publish(
         if qos < 0 or qos > 2:
             raise ValueError('Invalid QoS level.')
 
-        if isinstance(payload, str):
-            local_payload = payload.encode('utf-8')
-        elif isinstance(payload, (bytes, bytearray)):
-            local_payload = payload
-        elif isinstance(payload, (int, float)):
-            local_payload = str(payload).encode('ascii')
-        elif payload is None:
-            local_payload = b''
-        else:
-            raise TypeError(
-                'payload must be a string, bytearray, int, float or None.')
+        local_payload = _encode_payload(payload)
 
         if len(local_payload) > 268435455:
             raise ValueError('Payload too large.')
@@ -1820,18 +1831,7 @@ def will_set(
             raise ValueError(
                 "The properties argument must be an instance of the Properties class.")
 
-        if isinstance(payload, str):
-            self._will_payload = payload.encode('utf-8')
-        elif isinstance(payload, (bytes, bytearray)):
-            self._will_payload = payload
-        elif isinstance(payload, (int, float)):
-            self._will_payload = str(payload).encode('ascii')
-        elif payload is None:
-            self._will_payload = b""
-        else:
-            raise TypeError(
-                'payload must be a string, bytearray, int, float or None.')
-
+        self._will_payload = _encode_payload(payload)
         self._will = True
         self._will_topic = topic.encode('utf-8')
         self._will_qos = qos
@@ -2857,8 +2857,7 @@ def _pack_remaining_length(
                 return packet
 
     def _pack_str16(self, packet: bytearray, data: bytes | str) -> None:
-        if isinstance(data, str):
-            data = data.encode('utf-8')
+        data = _force_bytes(data)
         packet.extend(struct.pack("!H", len(data)))
         packet.extend(data)