WIP: Simplify python context code

- Needed to add a custom __new__ to Transport because its constructor
  parameters aren't compatible with the Wrapper class.
- Generalised wrap static method where possible

- Work on type annotations

python/cproton.py

@@ -340,24 +340,14 @@ def pn_collector_put_pyref(collector, obj, etype):
     lib.pn_collector_put_py(collector, d, etype.number)
 
 
-def pn_record_def_py(record):
-    lib.pn_record_def_py(record)
-
-
 def pn_record_get_py(record):
     d = lib.pn_record_get_py(record)
     if d == ffi.NULL:
-        return None
-    return ffi.from_handle(d)
-
-
-def pn_record_set_py(record, value):
-    if value is None:
-        d = ffi.NULL
-    else:
-        d = ffi.new_handle(value)
+        d = ffi.new_handle({})
         retained_objects.add(d)
-    lib.pn_record_set_py(record, d)
+        lib.pn_record_def_py(record)
+        lib.pn_record_set_py(record, d)
+    return ffi.from_handle(d)
 
 
 def pn_event_class_name(event):

python/proton/_delivery.py

@@ -24,11 +24,11 @@
     pn_delivery_writable, pn_disposition_annotations, pn_disposition_condition, pn_disposition_data, \
     pn_disposition_get_section_number, pn_disposition_get_section_offset, pn_disposition_is_failed, \
     pn_disposition_is_undeliverable, pn_disposition_set_failed, pn_disposition_set_section_number, \
-    pn_disposition_set_section_offset, pn_disposition_set_undeliverable, pn_disposition_type, \
-    isnull
+    pn_disposition_set_section_offset, pn_disposition_set_undeliverable, pn_disposition_type
 
 from ._condition import cond2obj, obj2cond
 from ._data import dat2obj, obj2dat
+from ._transport import Transport
 from ._wrapper import Wrapper
 
 from enum import IntEnum
@@ -39,7 +39,7 @@
     from ._condition import Condition
     from ._data import PythonAMQPData, symbol
     from ._endpoints import Receiver, Sender  # circular import
-    from ._reactor import Connection, Session, Transport
+    from ._reactor import Connection, Session
 
 
 class DispositionType(IntEnum):
@@ -277,19 +277,12 @@ class Delivery(Wrapper):
     delivery being settled.
     """
 
-    @staticmethod
-    def wrap(impl):
-        if isnull(impl):
-            return None
-        else:
-            return Delivery(impl)
+    get_context = pn_delivery_attachments
 
     def __init__(self, impl):
-        Wrapper.__init__(self, impl, pn_delivery_attachments)
-
-    def _init(self) -> None:
-        self.local = Disposition(pn_delivery_local(self._impl), True)
-        self.remote = Disposition(pn_delivery_remote(self._impl), False)
+        if self.Uninitialized():
+            self.local = Disposition(pn_delivery_local(self._impl), True)
+            self.remote = Disposition(pn_delivery_remote(self._impl), False)
 
     @property
     def tag(self) -> str:
@@ -414,7 +407,7 @@ def connection(self) -> 'Connection':
         return self.session.connection
 
     @property
-    def transport(self) -> 'Transport':
+    def transport(self) -> Optional[Transport]:
         """
         The :class:`Transport` bound to the :class:`Connection` over which
         the delivery was sent or received.

python/proton/_endpoints.py

@@ -54,8 +54,7 @@
     pn_terminus_is_dynamic, pn_terminus_outcomes, pn_terminus_properties, pn_terminus_set_address, \
     pn_terminus_set_distribution_mode, pn_terminus_set_durability, pn_terminus_set_dynamic, \
     pn_terminus_set_expiry_policy, pn_terminus_set_timeout, pn_terminus_set_type, \
-    pn_link_properties, pn_link_remote_properties, \
-    isnull
+    pn_link_properties, pn_link_remote_properties
 
 from ._condition import cond2obj, obj2cond
 from ._data import Data, dat2obj, obj2dat, PropertyDict, SymbolList
@@ -64,7 +63,7 @@
 from ._handler import Handler
 from ._transport import Transport
 from ._wrapper import Wrapper
-from typing import Dict, List, Optional, Union, TYPE_CHECKING, Any
+from typing import Any, Dict, List, Optional, Union, TYPE_CHECKING
 
 if TYPE_CHECKING:
     from ._condition import Condition
@@ -112,7 +111,7 @@ class Endpoint(object):
     REMOTE_CLOSED = PN_REMOTE_CLOSED
     """ The remote endpoint state is closed. """
 
-    def _init(self) -> None:
+    def __init__(self) -> None:
         self.condition: Optional['Condition'] = None
         self._handler: Optional[Handler] = None
 
@@ -159,26 +158,17 @@ class Connection(Wrapper, Endpoint):
     A representation of an AMQP connection.
     """
 
-    @staticmethod
-    def wrap(impl):
-        if isnull(impl):
-            return None
-        else:
-            return Connection(impl)
+    constructor = pn_connection
+    get_context = pn_connection_attachments
 
     def __init__(self, impl: Any = None) -> None:
-        if impl is None:
-            Wrapper.__init__(self, constructor=pn_connection, get_context=pn_connection_attachments)
-        else:
-            Wrapper.__init__(self, impl, pn_connection_attachments)
-
-    def _init(self) -> None:
-        Endpoint._init(self)
-        self.offered_capabilities_list = None
-        self.desired_capabilities_list = None
-        self.properties = None
-        self.url = None
-        self._acceptor = None
+        if self.Uninitialized():
+            Endpoint.__init__(self)
+            self.offered_capabilities_list = None
+            self.desired_capabilities_list = None
+            self.properties = None
+            self.url = None
+            self._acceptor = None
 
     def _get_attachments(self):
         return pn_connection_attachments(self._impl)
@@ -550,15 +540,12 @@ def properties(self, properties_dict: Optional[Union[PropertyDict, Dict[str, 'Py
 
 class Session(Wrapper, Endpoint):
     """A container of links"""
-    @staticmethod
-    def wrap(impl):
-        if isnull(impl):
-            return None
-        else:
-            return Session(impl)
+
+    get_context = pn_session_attachments
 
     def __init__(self, impl):
-        Wrapper.__init__(self, impl, pn_session_attachments)
+        if self.Uninitialized():
+            Endpoint.__init__(self)
 
     def _get_attachments(self):
         return pn_session_attachments(self._impl)
@@ -714,21 +701,18 @@ class Link(Wrapper, Endpoint):
     RCV_SECOND = PN_RCV_SECOND
     """The receiver will only settle deliveries after the sender settles."""
 
-    @staticmethod
-    def wrap(impl):
-        if isnull(impl):
-            return None
+    get_context = pn_link_attachments
+
+    def __new__(cls, impl) -> 'Link':
         if pn_link_is_sender(impl):
-            return Sender(impl)
+            return super().__new__(Sender, impl)
         else:
-            return Receiver(impl)
+            return super().__new__(Receiver, impl)
 
     def __init__(self, impl):
-        Wrapper.__init__(self, impl, pn_link_attachments)
-
-    def _init(self) -> None:
-        Endpoint._init(self)
-        self.properties = None
+        if self.Uninitialized():
+            Endpoint.__init__(self)
+            self.properties = None
 
     def _get_attachments(self):
         return pn_link_attachments(self._impl)

python/proton/_transport.py

@@ -92,27 +92,32 @@ def wrap(impl: Optional[Callable]) -> Optional['Transport']:
         else:
             return Transport(impl=impl)
 
+    constructor = pn_transport
+    get_context = pn_transport_attachments
+
+    def __new__(
+            cls,
+            mode: Optional[int] = None,
+            impl=None,
+    ) -> 'Transport':
+        return super().__new__(cls, impl)
+
     def __init__(
             self,
-            mode: 'Optional[int]' = None,
-            impl: 'Callable' = None,
+            mode: Optional[int] = None,
+            impl=None,
     ) -> None:
-        if impl is None:
-            Wrapper.__init__(self, constructor=pn_transport, get_context=pn_transport_attachments)
-        else:
-            Wrapper.__init__(self, impl, pn_transport_attachments)
         if mode == Transport.SERVER:
             pn_transport_set_server(self._impl)
         elif mode is None or mode == Transport.CLIENT:
             pass
         else:
             raise TransportException("Cannot initialise Transport from mode: %s" % str(mode))
-
-    def _init(self) -> None:
-        self._sasl = None
-        self._ssl = None
-        self._reactor = None
-        self._connect_selectable = None
+        if self.Uninitialized():
+            self._sasl = None
+            self._ssl = None
+            self._reactor = None
+            self._connect_selectable = None
 
     def _check(self, err: int) -> int:
         if err < 0:
@@ -468,7 +473,9 @@ def sasl(self) -> 'SASL':
 
         :return: SASL object associated with this transport.
         """
-        return SASL(self)
+        if not self._sasl:
+            self._sasl = SASL(self)
+        return self._sasl
 
     def ssl(self, domain: Optional['SSLDomain'] = None, session_details: Optional['SSLSessionDetails'] = None) -> 'SSL':
         """
@@ -512,7 +519,7 @@ class SASLException(TransportException):
     pass
 
 
-class SASL(Wrapper):
+class SASL:
     """
     The SASL layer is responsible for establishing an authenticated
     and/or encrypted tunnel over which AMQP frames are passed between
@@ -542,9 +549,14 @@ def extended() -> bool:
         """
         return pn_sasl_extended()
 
-    def __init__(self, transport: Transport) -> None:
-        Wrapper.__init__(self, transport._impl, pn_transport_attachments)
-        self._sasl = pn_sasl(transport._impl)
+    def __new__(cls, transport: Transport) -> 'SASL':
+        if not transport._sasl:
+            sasl = super().__new__(cls)
+            sasl._sasl = pn_sasl(transport._impl)
+            transport._sasl = sasl
+            return sasl
+        else:
+            return transport._sasl
 
     def _check(self, err):
         if err < 0: