fix(edge): Handle invalid input types when creating TargetHandle (#3368)

* fix(edge): Handle invalid input types when creating TargetHandle

* test(edge): add test for raising error on invalid target handle

* fix: mypy error union-attr

---------

Co-authored-by: italojohnny <italojohnnydosanjos@gmail.com>

src/backend/base/langflow/graph/edge/base.py

@@ -23,7 +23,23 @@ class Edge:
             self._target_handle = cast(TargetHandleDict, data.get("targetHandle", {}))
             self.source_handle: SourceHandle = SourceHandle(**self._source_handle)
             if isinstance(self._target_handle, dict):
-                self.target_handle: TargetHandle = TargetHandle(**self._target_handle)
+                try:
+                    self.target_handle: TargetHandle = TargetHandle(**self._target_handle)
+                except Exception as e:
+                    if "inputTypes" in self._target_handle and self._target_handle["inputTypes"] is None:
+                        # Check if self._target_handle['fieldName']
+                        if hasattr(target, "_custom_component"):
+                            display_name = getattr(target._custom_component, "display_name", "")
+                            raise ValueError(
+                                f"Component {display_name} field '{self._target_handle['fieldName']}' might not be a valid input."
+                            ) from e
+                        else:
+                            raise ValueError(
+                                f"Field '{self._target_handle['fieldName']}' on {target.display_name} might not be a valid input."
+                            ) from e
+                    else:
+                        raise e
+
             else:
                 raise ValueError("Target handle is not a dictionary")
             self.target_param = self.target_handle.field_name

src/backend/tests/unit/graph/edge/test_edge_base.py

@@ -0,0 +1,35 @@
+import pytest
+
+from langflow.components.inputs.ChatInput import ChatInput
+from langflow.components.models.OpenAIModel import OpenAIModelComponent
+from langflow.components.outputs.ChatOutput import ChatOutput
+from langflow.components.prompts.Prompt import PromptComponent
+from langflow.graph.graph.base import Graph
+
+
+@pytest.fixture
+def client():
+    pass
+
+
+def test_edge_raises_error_on_invalid_target_handle(client):
+    template = """Answer the user as if you were a pirate.
+
+User: {user_input}
+
+Answer:
+"""
+    chat_input = ChatInput()
+    prompt_component = PromptComponent()
+    prompt_component.set(
+        template=template,
+        user_input=chat_input.message_response,
+    )
+
+    openai_component = OpenAIModelComponent()
+    openai_component.set(input_values=prompt_component.build_prompt)
+
+    chat_output = ChatOutput()
+    chat_output.set(input_value=openai_component.text_response)
+    with pytest.raises(ValueError, match="Component OpenAI field 'input_values' might not be a valid input."):
+        Graph(start=chat_input, end=chat_output)