feat: allow passing a Component to the set method (#3597)

* refactor: Add _find_matching_output_method to Component class

* feat: allow components to be passed in set method

* fix: Add test for graph set method with valid component

* set value variable to the output callable

* refactor: Update test_component.py to use set_component method

This commit refactors the test_component.py file in the custom_component directory. The test_set_invalid_input() function has been renamed to test_set_component() to better reflect its purpose. Additionally, the test_set_component() function now sets the agent parameter using the set_component() method instead of raising a ValueError. This change improves the readability and maintainability of the code.

* refactor: Fix formatting issue in _build_error_string_from_matching_pairs

The _build_error_string_from_matching_pairs method in the Component class had a formatting issue when input types were empty. This commit fixes the issue by adding a check for empty input types and providing an empty list as a fallback. This improves the accuracy and readability of the error string generated by the method.

* fix(component.py): add validation to ensure output method is a string to prevent potential runtime errors

src/backend/base/langflow/custom/custom_component/component.py

@@ -310,9 +310,40 @@ def _method_is_valid_output(self, method: Callable):
         )
         return method_is_output
 
+    def _build_error_string_from_matching_pairs(self, matching_pairs: list[tuple[Output, Input]]):
+        text = ""
+        for output, input_ in matching_pairs:
+            text += f"{output.name}[{','.join(output.types)}]->{input_.name}[{','.join(input_.input_types or [])}]\n"
+        return text
+
+    def _find_matching_output_method(self, value: "Component"):
+        # get all outputs of the value component
+        outputs = value.outputs
+        # check if the any of the types in the output.types matches ONLY one input in the current component
+        matching_pairs = []
+        for output in outputs:
+            for input_ in self.inputs:
+                for output_type in output.types:
+                    if input_.input_types and output_type in input_.input_types:
+                        matching_pairs.append((output, input_))
+        if len(matching_pairs) > 1:
+            matching_pairs_str = self._build_error_string_from_matching_pairs(matching_pairs)
+            raise ValueError(
+                f"There are multiple outputs from {value.__class__.__name__} that can connect to inputs in {self.__class__.__name__}: {matching_pairs_str}"
+            )
+        output, input_ = matching_pairs[0]
+        if not isinstance(output.method, str):
+            raise ValueError(f"Method {output.method} is not a valid output of {value.__class__.__name__}")
+        return getattr(value, output.method)
+
     def _process_connection_or_parameter(self, key, value):
         _input = self._get_or_create_input(key)
         # We need to check if callable AND if it is a method from a class that inherits from Component
+        if isinstance(value, Component):
+            # We need to find the Output that can connect to an input of the current component
+            # if there's more than one output that matches, we need to raise an error
+            # because we don't know which one to connect to
+            value = self._find_matching_output_method(value)
         if callable(value) and self._inherits_from_component(value):
             try:
                 self._method_is_valid_output(value)

src/backend/tests/unit/custom/custom_component/test_component.py

@@ -18,11 +18,9 @@ def test_set_invalid_output():
         chatoutput.set(input_value=chatinput.build_config)
 
 
-def test_set_invalid_input():
+def test_set_component():
     crewai_agent = CrewAIAgentComponent()
     task = SequentialTaskComponent()
-    with pytest.raises(
-        ValueError,
-        match="You set CrewAI Agent as value for `agent`. You should pass one of the following: 'build_output'",
-    ):
-        task.set(agent=crewai_agent)
+    task.set(agent=crewai_agent)
+    assert task._edges[0]["source"] == crewai_agent._id
+    assert crewai_agent in task._components

src/backend/tests/unit/graph/graph/test_base.py

@@ -2,9 +2,11 @@
 
 import pytest
 
+from langflow.components.agents.ToolCallingAgent import ToolCallingAgentComponent
 from langflow.components.inputs.ChatInput import ChatInput
 from langflow.components.outputs.ChatOutput import ChatOutput
 from langflow.components.outputs.TextOutput import TextOutputComponent
+from langflow.components.tools.YfinanceTool import YfinanceToolComponent
 from langflow.graph.graph.base import Graph
 from langflow.graph.graph.constants import Finish
 
@@ -139,3 +141,16 @@ def test_graph_functional_start_end():
     assert len(results) == len(ids) + 1
     assert all(result.vertex.id in ids for result in results if hasattr(result, "vertex"))
     assert results[-1] == Finish()
+
+
+def test_graph_set_with_invalid_component():
+    chat_input = ChatInput(_id="chat_input")
+    chat_output = ChatOutput(input_value="test", _id="chat_output")
+    with pytest.raises(ValueError, match="There are multiple outputs"):
+        chat_output.set(sender_name=chat_input)
+
+
+def test_graph_set_with_valid_component():
+    tool = YfinanceToolComponent()
+    tool_calling_agent = ToolCallingAgentComponent()
+    tool_calling_agent.set(tools=[tool])