Fix/ parse port spec port as sender or recvr (#2728)

* • port.py
  _parse_port_spec(): fix assignment of port if port_spec[PORT_SPEC_ARG] is a dict with a projection specified

psyneulink/core/components/ports/port.py

@@ -2884,22 +2884,49 @@ def _parse_port_spec(port_type=None,
 
         # If it is a Port specification dictionary
         if isinstance(port_spec[PORT_SPEC_ARG], dict):
-
-            # If the Port specification has a Projection that has a sender already assigned,
-            #    then return that Port with the Projection assigned to it
-            #    (this occurs, for example, if an instantiated ControlSignal is used to specify a parameter
-            # FIX: JDC 7/8/23 ??WHAT IF PORT SPECIFICATION DICT HAS OTHER SPECS, SUCH AS SIZE?
-            #      POSSIBLY THIS SHOULD ONLY BE CALLED IF DICT CONTAINS *ONLY* A PROJECTION SPEC?
+            # If the Port specification has a Projection specification (instantiated or in deferred_init)
+            # (used to define its connection) then return port specified in the Projection.
+            # This can either the sender or the receiver of the specified Projection, depending on the caller:
+            # - if the sender is specified in the Projection, return port = receiver
+            #   (e.g., projection is a ControlProjections with its receiver (ParameterPort) specified,
+            #          so return port = sender -- i.e., ControlSignal to which ControlProjection should be connected)
+            # - if the receiver is specified in the Projection, return port = sender
+            #   (e.g., projection is from an OutputPort with its sender specified,
+            #          so return the port = receiver -- i.e., InputPort to which Projection should be connected)
+            # FIX: WHAT IF PORT SPECIFICATION DICT HAS OTHER SPECS, SUCH AS SIZE?
+            # FIX: POSSIBLY THIS SHOULD BE CALLED ONLY IF DICT CONTAINS *ONLY* A PROJECTION SPEC?
             try:
                 projection = port_spec[PORT_SPEC_ARG][PROJECTIONS]
                 if isinstance(projection, list):
                     assert len(port_spec[PORT_SPEC_ARG][PROJECTIONS])==1
                     projection = port_spec[PORT_SPEC_ARG][PROJECTIONS][0]
-                    port = projection.sender
+                if projection.initialization_status == ContextFlags.INITIALIZED:
+                    sender = projection.sender
+                    receiver = projection.receiver
                 elif projection.initialization_status == ContextFlags.DEFERRED_INIT:
-                    port = projection._init_args[SENDER]
+                    sender = projection._init_args[SENDER]
+                    receiver = projection._init_args[RECEIVER]
+                else:
+                    assert False, f"PROGRAM ERROR: Projection ('{projection.name}') specified for" \
+                                  f" {port_type.__name__} of '{owner.name}' has unrcognized initialization_status: " \
+                                  f"{projection.initialization_status.name}"
+                # Check whether sender and/or receiver is an instantiated Port
+                sender_instantiated = isinstance(sender, Port)
+                if sender_instantiated:
+                    sender_instantiated = sender.initialization_status == ContextFlags.INITIALIZED
+                receiver_instantiated = isinstance(receiver, Port)
+                if receiver_instantiated:
+                    receiver_instantiated = receiver.initialization_status == ContextFlags.INITIALIZED
+                # Ensure that *either* sender or receiver is an instantiated Port, but *not both*
+                assert sender_instantiated ^ receiver_instantiated, \
+                    f"PROGRAM ERROR: Projection ('{projection.name}') specified for" \
+                    f" {port_type.__name__} of '{owner.name}' has both sender and receiver instantiated: " \
+                    f"sender: '{sender.name}'; receiver: '{receiver.name}'"
+                if sender_instantiated:
+                    port = projection.receiver
                 else:
                     port = projection.sender
+
                 if port.initialization_status == ContextFlags.DEFERRED_INIT:
                     port._init_args[PROJECTIONS] = projection
                 else: