Add version 2 of user-callback

This allow to access reason code & properties on on_publish

ChangeLog.txt

@@ -1,12 +1,18 @@
 v2.0.0 - 2023-xx-xx
 ===================
 
+- **BREAKING** Added callback_api_version. This break *ALL* users of paho-mqtt Client class.
+  See migrations.md for details on how to upgrade.
+  tl; dr; add CallbackAPIVersion.VERSION1 to first argument of Client()
 - **BREAKING** Drop support for Python 2.7, Python 3.5 and Python 3.6
   Minimum tested version is Python 3.7
   Python version up to Python 3.12 are tested.
 - **BREAKING** connect_srv changed it signature to take an additional bind_port parameter.
   This is a breaking change, but in previous version connect_srv was broken anyway.
   Closes #493.
+- Add version 2 of user-callback which allow to access MQTTv5 reason code & properties that were
+  missing from on_publish callback. Also it's more consistent in parameter order or between
+  MQTTv3 and MQTTv5.
 - Add types to Client class, which caused few change which should be compatible.
   Known risk of breaking changes:
   - Use enum for returned error code (like MQTT_ERR_SUCCESS). It use an IntEnum

migrations.md

@@ -0,0 +1,189 @@
+# Migration
+
+## Change between version 1.x and 2.0
+
+### Improved typing
+
+Version 2.0 improved typing, but this would be compatible with existing code.
+The most likely issue are some integer that are now better type, like `dup` on MQTTMessage.
+
+That means that code that used `if msg.dup == 1:` will need to be change to `if msg.dup:` (the later version
+for with both paho-mqtt 1.x and 2.0).
+
+### Versioned the user callbacks
+
+Version 2.0 of paho-mqtt introduced versioning of user-callback. To fix some inconsistency in callback
+arguments and to provide better support for MQTTv5, version 2.0 changed the arguments passed to user-callback.
+
+You can still use old version of callback, you are just require to tell paho-mqtt that you opt for this
+version. For that just change your client creation from:
+```
+# OLD code
+>>> mqttc = mqtt.Client()
+
+# NEW code
+>>> mqttc = mqtt.Client(mqtt.CallbackAPIVersion.VERSION1)
+```
+
+That it, remaining of the code could stay unchanged.
+
+The version 1 of callback is deprecated, but is still supported in version 2.x. If you want to upgrade to newer version of API callback, you will need to update your callbacks:
+
+#### on_connect
+
+```
+# OLD code for MQTTv3
+def on_connect(client, userdata, flags, rc):
+    if flags["session present"] == 1:
+        # ...
+    if rc == 0:
+        # success connect
+    if rc > 0:
+        # error processing
+
+# OLD code for MQTTv5
+def on_connect(client, userdata, flags, reason_code, properties):
+    if flags["session present"] == 1:
+        # ...
+    if reason_code == 0:
+        # success connect
+
+# NEW code for both version
+def on_connect(client, userdata, flags, reason_code, properties):
+    if flags.session_present:
+        # ...
+    if reason_code == 0:
+        # success connect
+    if reason_code > 0:
+        # error processing
+```
+
+Be careful that for MQTTv3, `rc` (an integer) changed to `reason_code` (an instance of ReasonCodes), and the numeric value changed.
+The numeric value 0 means success for both, so as in above example, using `reason_code == 0`, `reason_code != 0` or other comparison with zero
+is fine.
+But if you had comparison with other value, you will need to update the code. It's recommended to compare to string value:
+
+```
+# OLD code for MQTTv3
+def on_connect(client, userdata, flags, rc):
+    if rc == 1:
+        # handle bad protocol version
+    if rc == CONNACK_REFUSED_IDENTIFIER_REJECTED:
+        # handle bad identifier
+
+# NEW code
+def on_connect(client, userdata, flags, reason_code, properties):
+    if rc == "Unsupported protocol version":
+        # handle bad protocol version
+    if rc == "Client identifier not valid":
+        # handle bad identifier
+```
+
+#### on_disconnect
+
+```
+# OLD code for MQTTv3
+def on_disconnect(client, userdata, rc):
+    if rc == 0:
+        # success disconnect
+    if rc > 0:
+        # error processing
+
+# OLD code for MQTTv5
+def on_disconnect(client, userdata, reason_code, properties):
+    if reason_code:
+        # error processing
+
+# NEW code for both version
+def on_disconnect(client, userdata, flags, reason_code, properties):
+    if reason_code == 0:
+        # success disconnect
+    if reason_code > 0:
+        # error processing
+```
+
+
+#### on_subscribe
+
+```
+# OLD code for MQTTv3
+def on_subscribe(client, userdata, mid, granted_qos):
+    for sub_result in granted_qos:
+        if sub_result == 1:
+            # process QoS == 1
+        if sub_result == 0x80:
+            # error processing
+
+# OLD code for MQTTv5
+def on_disconnect(client, userdata, mid, reason_codes, properties):
+    for sub_result in reason_codes:
+        if sub_result == 1:
+            # process QoS == 1
+        # Any reason code >= 128 is a failure.
+        if sub_result >= 128:
+            # error processing
+
+# NEW code for both version
+def on_subscribe(client, userdata, mid, reason_codes, properties):
+    for sub_result in reason_codes:
+        if sub_result == 1:
+            # process QoS == 1
+        # Any reason code >= 128 is a failure.
+        if sub_result >= 128:
+            # error processing
+```
+
+
+#### on_unsubscribe
+
+```
+# OLD code for MQTTv3
+def on_unsubscribe(client, userdata, mid):
+    # ...
+
+# OLD code for MQTTv5
+def on_unsubscribe(client, userdata, mid, properties, reason_codes):
+    # In OLD version, reason_codes could be a list or a single ReasonCodes object
+    if isinstance(reason_codes, list):
+        for unsub_result in reason_codes:
+            # Any reason code >= 128 is a failure.
+            if reason_codes[0] >= 128:
+                # error processing
+    else:
+        # Any reason code >= 128 is a failure.
+        if reason_codes > 128:
+            # error processing
+
+
+# NEW code for both version
+def on_subscribe(client, userdata, mid, reason_codes, properties):
+    # In NEW version, reason_codes is always a list. Empty for MQTTv3
+    for unsub_result in reason_codes:
+        # Any reason code >= 128 is a failure.
+        if reason_codes[0] >= 128:
+            # error processing
+```
+
+
+#### on_publish
+
+```
+# OLD code
+def on_publish(client, userdata, mid):
+    # ...
+
+
+# NEW code
+def on_publish(client, userdata, mid, reason_codes, properties):
+    # ...
+```
+
+
+#### on_message
+
+No change for this callback.
+```
+# OLD & NEW code
+def on_message(client, userdata, message):
+    # ...
+```

pyproject.toml

@@ -90,6 +90,9 @@ disallow_untyped_defs = true
 [tool.pytest.ini_options]
 addopts = ["-r", "xs"]
 testpaths = "tests src"
+filterwarnings = [
+    "ignore:Callback API version 1 is deprecated, update to latest version"
+]
 
 [tool.ruff]
 exclude = ["test/lib/python/*"]