RecursionError when Pipeline Component with Enum in Data Raises Exception

[tommyjs007]

When a Haystack pipeline component raises an exception during execution, it triggers a RecursionError: maximum recursion depth exceeded instead of properly propagating the original exception. This issue is specifically triggered when data containing Python Enum values is passed between components.

Steps to Reproduce

Create a pipeline with at least two connected components
Have the first component output data containing an Enum value
Have the second component raise an exception during its run() method
Execute the pipeline

You will get
RecursionError: maximum recursion depth exceeded

Minimal Reproducible Example

from enum import Enum
from typing import List, Dict
from haystack import Pipeline, component
from haystack.dataclasses import Document

class SomeEnum(Enum):
    ONE = "one"
    TWO = "two"

@component
class TextProcessor:
    def __init__(self, prefix: str = "PROCESSED"):
        self.prefix = prefix

    @component.output_types(documents=List[Document], data=List[Dict])
    def run(self, documents: List[Document]) -> Dict[str, any]:
        # Critical: data contains an Enum value
        return {"documents": [], "data": [{"key": SomeEnum.ONE}]}

@component
class ContentEnricher:
    @component.output_types(documents=List[Document])
    def run(self, documents: List[Document], data: List[Dict]) -> Dict[str, List[Document]]:
        raise Exception("fail")

# Build pipeline
pipeline = Pipeline()
pipeline.add_component("text_processor", TextProcessor(prefix="DEMO"))
pipeline.add_component("content_enricher", ContentEnricher())
pipeline.connect("text_processor.documents", "content_enricher.documents")
pipeline.connect("text_processor.data", "content_enricher.data")

# Run pipeline - triggers RecursionError
result = pipeline.run({"text_processor": {"documents": []}})