feat: use full connection data to route I/O

.gitignore

@@ -133,4 +133,4 @@ dmypy.json
 # Canals
 drafts/
 .canals_debug/
-test/**/*.png
+test/**/*.png

canals/component/component.py

@@ -72,6 +72,7 @@
 import inspect
 from typing import Protocol, runtime_checkable, Any
 from types import new_class
+from copy import deepcopy
 
 from canals.component.sockets import InputSocket, OutputSocket
 from canals.errors import ComponentError
@@ -121,10 +122,16 @@ def __call__(cls, *args, **kwargs):
         # Before returning, we have the chance to modify the newly created
         # Component instance, so we take the chance and set up the I/O sockets
 
-        # If the __init__ called component.set_output_types(), __canals_output__ is already populated
+        # If `component.set_output_types()` was called in the component constructor,
+        # `__canals_output__` is already populated, no need to do anything.
         if not hasattr(instance, "__canals_output__"):
-            # if the run method was decorated, it has a _output_types_cache field assigned
-            instance.__canals_output__ = getattr(instance.run, "_output_types_cache", {})
+            # If that's not the case, we need to populate `__canals_output__`
+            #
+            # If the `run` method was decorated, it has a `_output_types_cache` field assigned
+            # that stores the output specification.
+            # We deepcopy the content of the cache to transfer ownership from the class method
+            # to the actual instance, so that different instances of the same class won't share this data.
+            instance.__canals_output__ = deepcopy(getattr(instance.run, "_output_types_cache", {}))
 
         # If the __init__ called component.set_input_types(), __canals_input__ is already populated
         if not hasattr(instance, "__canals_input__"):
@@ -134,6 +141,7 @@ def __call__(cls, *args, **kwargs):
                 param: InputSocket(
                     name=param,
                     type=run_signature.parameters[param].annotation,
+                    is_mandatory=run_signature.parameters[param].default == inspect.Parameter.empty,
                 )
                 for param in list(run_signature.parameters)[1:]  # First is 'self' and it doesn't matter.
             }

canals/component/connection.py

@@ -0,0 +1,167 @@
+import itertools
+from typing import Optional, List, Tuple
+from dataclasses import dataclass
+
+from canals.component.sockets import InputSocket, OutputSocket
+from canals.type_utils import _type_name, _types_are_compatible
+from canals.errors import PipelineConnectError
+
+
+@dataclass
+class Connection:
+    sender: Optional[str]
+    sender_socket: Optional[OutputSocket]
+    receiver: Optional[str]
+    receiver_socket: Optional[InputSocket]
+
+    def __post_init__(self):
+        if self.sender and self.sender_socket and self.receiver and self.receiver_socket:
+            # Make sure the receiving socket isn't already connected, unless it's variadic. Sending sockets can be
+            # connected as many times as needed, so they don't need this check
+            if self.receiver_socket.senders and not self.receiver_socket.is_variadic:
+                raise PipelineConnectError(
+                    f"Cannot connect '{self.sender}.{self.sender_socket.name}' with '{self.receiver}.{self.receiver_socket.name}': "
+                    f"{self.receiver}.{self.receiver_socket.name} is already connected to {self.receiver_socket.senders}.\n"
+                )
+
+            self.sender_socket.receivers.append(self.receiver)
+            self.receiver_socket.senders.append(self.sender)
+
+    def __repr__(self):
+        if self.sender and self.sender_socket:
+            sender_repr = f"{self.sender}.{self.sender_socket.name} ({_type_name(self.sender_socket.type)})"
+        else:
+            sender_repr = "input needed"
+
+        if self.receiver and self.receiver_socket:
+            receiver_repr = f"({_type_name(self.receiver_socket.type)}) {self.receiver}.{self.receiver_socket.name}"
+        else:
+            receiver_repr = "output"
+
+        return f"{sender_repr} --> {receiver_repr}"
+
+    def __hash__(self):
+        """
+        Connection is used as a dictionary key in Pipeline, it must be hashable
+        """
+        return hash(
+            "-".join(
+                [
+                    self.sender if self.sender else "input",
+                    self.sender_socket.name if self.sender_socket else "",
+                    self.receiver if self.receiver else "output",
+                    self.receiver_socket.name if self.receiver_socket else "",
+                ]
+            )
+        )
+
+    @property
+    def is_mandatory(self) -> bool:
+        """
+        Returns True if the connection goes to a mandatory input socket, False otherwise
+        """
+        if self.receiver_socket:
+            return self.receiver_socket.is_mandatory
+        return False
+
+    @staticmethod
+    def from_list_of_sockets(
+        sender_node: str, sender_sockets: List[OutputSocket], receiver_node: str, receiver_sockets: List[InputSocket]
+    ) -> "Connection":
+        """
+        Find one single possible connection between two lists of sockets.
+        """
+        # List all sender/receiver combinations of sockets that match by type
+        possible_connections = [
+            (sender_sock, receiver_sock)
+            for sender_sock, receiver_sock in itertools.product(sender_sockets, receiver_sockets)
+            if _types_are_compatible(sender_sock.type, receiver_sock.type)
+        ]
+
+        # No connections seem to be possible
+        if not possible_connections:
+            connections_status_str = _connections_status(
+                sender_node=sender_node,
+                sender_sockets=sender_sockets,
+                receiver_node=receiver_node,
+                receiver_sockets=receiver_sockets,
+            )
+
+            # Both sockets were specified: explain why the types don't match
+            if len(sender_sockets) == len(receiver_sockets) and len(sender_sockets) == 1:
+                raise PipelineConnectError(
+                    f"Cannot connect '{sender_node}.{sender_sockets[0].name}' with '{receiver_node}.{receiver_sockets[0].name}': "
+                    f"their declared input and output types do not match.\n{connections_status_str}"
+                )
+
+            # Not both sockets were specified: explain there's no possible match on any pair
+            connections_status_str = _connections_status(
+                sender_node=sender_node,
+                sender_sockets=sender_sockets,
+                receiver_node=receiver_node,
+                receiver_sockets=receiver_sockets,
+            )
+            raise PipelineConnectError(
+                f"Cannot connect '{sender_node}' with '{receiver_node}': "
+                f"no matching connections available.\n{connections_status_str}"
+            )
+
+        # There's more than one possible connection
+        if len(possible_connections) > 1:
+            # Try to match by name
+            name_matches = [
+                (out_sock, in_sock) for out_sock, in_sock in possible_connections if in_sock.name == out_sock.name
+            ]
+            if len(name_matches) != 1:
+                # TODO allow for multiple connections at once if there is no ambiguity?
+                # TODO give priority to sockets that have no default values?
+                connections_status_str = _connections_status(
+                    sender_node=sender_node,
+                    sender_sockets=sender_sockets,
+                    receiver_node=receiver_node,
+                    receiver_sockets=receiver_sockets,
+                )
+                raise PipelineConnectError(
+                    f"Cannot connect '{sender_node}' with '{receiver_node}': more than one connection is possible "
+                    "between these components. Please specify the connection name, like: "
+                    f"pipeline.connect('{sender_node}.{possible_connections[0][0].name}', "
+                    f"'{receiver_node}.{possible_connections[0][1].name}').\n{connections_status_str}"
+                )
+
+        match = possible_connections[0]
+        return Connection(sender_node, match[0], receiver_node, match[1])
+
+
+def _connections_status(
+    sender_node: str, receiver_node: str, sender_sockets: List[OutputSocket], receiver_sockets: List[InputSocket]
+):
+    """
+    Lists the status of the sockets, for error messages.
+    """
+    sender_sockets_entries = []
+    for sender_socket in sender_sockets:
+        sender_sockets_entries.append(f" - {sender_socket.name}: {_type_name(sender_socket.type)}")
+    sender_sockets_list = "\n".join(sender_sockets_entries)
+
+    receiver_sockets_entries = []
+    for receiver_socket in receiver_sockets:
+        if receiver_socket.senders:
+            sender_status = f"sent by {','.join(receiver_socket.senders)}"
+        else:
+            sender_status = "available"
+        receiver_sockets_entries.append(
+            f" - {receiver_socket.name}: {_type_name(receiver_socket.type)} ({sender_status})"
+        )
+    receiver_sockets_list = "\n".join(receiver_sockets_entries)
+
+    return f"'{sender_node}':\n{sender_sockets_list}\n'{receiver_node}':\n{receiver_sockets_list}"
+
+
+def parse_connect_string(connection: str) -> Tuple[str, Optional[str]]:
+    """
+    Returns component-connection pairs from a connect_to/from string
+    """
+    if "." in connection:
+        split_str = connection.split(".", maxsplit=1)
+        return (split_str[0], split_str[1])
+    return connection, None

canals/component/sockets.py

@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: 2022-present deepset GmbH <[email protected]>
 #
 # SPDX-License-Identifier: Apache-2.0
-from typing import get_origin, get_args, List, Type, Union
+from typing import get_args, List, Type
 import logging
 from dataclasses import dataclass, field
 
@@ -15,12 +15,11 @@
 class InputSocket:
     name: str
     type: Type
-    is_optional: bool = field(init=False)
+    is_mandatory: bool = True
     is_variadic: bool = field(init=False)
-    sender: List[str] = field(default_factory=list)
+    senders: List[str] = field(default_factory=list)
 
     def __post_init__(self):
-        self.is_optional = get_origin(self.type) is Union and type(None) in get_args(self.type)
         try:
             # __metadata__ is a tuple
             self.is_variadic = self.type.__metadata__[0] == CANALS_VARIADIC_ANNOTATION
@@ -39,3 +38,4 @@ def __post_init__(self):
 class OutputSocket:
     name: str
     type: type
+    receivers: List[str] = field(default_factory=list)

canals/pipeline/descriptions.py

@@ -19,19 +19,18 @@ def find_pipeline_inputs(graph: networkx.MultiDiGraph) -> Dict[str, List[InputSo
     input sockets, including all such sockets with default values.
     """
     return {
-        name: [socket for socket in data.get("input_sockets", {}).values() if not socket.sender]
+        name: [socket for socket in data.get("input_sockets", {}).values() if not socket.senders or socket.is_variadic]
         for name, data in graph.nodes(data=True)
     }
 
 
-def find_pipeline_outputs(graph) -> Dict[str, List[OutputSocket]]:
+def find_pipeline_outputs(graph: networkx.MultiDiGraph) -> Dict[str, List[OutputSocket]]:
     """
     Collect components that have disconnected output sockets. They define the pipeline output.
     """
     return {
-        node: list(data.get("output_sockets", {}).values())
-        for node, data in graph.nodes(data=True)
-        if not graph.out_edges(node)
+        name: [socket for socket in data.get("output_sockets", {}).values() if not socket.receivers]
+        for name, data in graph.nodes(data=True)
     }
 
 
@@ -40,7 +39,7 @@ def describe_pipeline_inputs(graph: networkx.MultiDiGraph):
     Returns a dictionary with the input names and types that this pipeline accepts.
     """
     inputs = {
-        comp: {socket.name: {"type": socket.type, "is_optional": socket.is_optional} for socket in data}
+        comp: {socket.name: {"type": socket.type, "is_mandatory": socket.is_mandatory} for socket in data}
         for comp, data in find_pipeline_inputs(graph).items()
         if data
     }

canals/pipeline/draw/draw.py

@@ -95,7 +95,7 @@ def _prepare_for_drawing(graph: networkx.MultiDiGraph, style_map: Dict[str, str]
     graph.add_node("input")
     for node, in_sockets in find_pipeline_inputs(graph).items():
         for in_socket in in_sockets:
-            if not in_socket.sender and not in_socket.is_optional:
+            if not in_socket.senders and in_socket.is_mandatory:
                 # If this socket has no sender it could be a socket that receives input
                 # directly when running the Pipeline. We can't know that for sure, in doubt
                 # we draw it as receiving input directly.