refactor: Validate name overlap between inputs and outputs in FrontendNode

The code changes in `frontend_node/base.py` add a new method `validate_name_overlap` to the `FrontendNode` class. This method checks if any of the output names overlap with any of the input names and raises a `ValueError` if there is a duplication. This refactor improves the consistency and correctness of the code. The commit message follows the established convention of using a prefix to indicate the type of change.

src/backend/base/langflow/custom/utils.py

@@ -373,6 +373,8 @@ def build_custom_component_template_from_inputs(
         return_types = [format_type(return_type) for return_type in return_types]
         output.add_types(return_types)
         output.set_selected()
+    # Validate that there is not name overlap between inputs and outputs
+    frontend_node.validate_name_overlap()
     # ! This should be removed when we have a better way to handle this
     frontend_node.get_base_classes_from_outputs()
     reorder_fields(frontend_node, custom_component._get_field_order())

src/backend/base/langflow/template/frontend_node/base.py

@@ -102,6 +102,17 @@ class FrontendNode(BaseModel):
     def get_base_classes_from_outputs(self) -> list[str]:
         self.base_classes = [output_type for output in self.outputs for output_type in output.types]
 
+    def validate_name_overlap(self) -> None:
+        # Check if any of the output names overlap with the any of the inputs
+        output_names = [output.name for output in self.outputs]
+        input_names = [input_.name for input_ in self.template.fields]
+        overlap = set(output_names).intersection(input_names)
+        if overlap:
+            overlap = ", ".join(map(lambda x: f"'{x}'", overlap))
+            raise ValueError(
+                f"There should be no overlap between input and output names. Names {overlap} are duplicated."
+            )
+
     def add_base_class(self, base_class: Union[str, List[str]]) -> None:
         """Adds a base class to the frontend node."""
         if isinstance(base_class, str):