Remove error suppressor in async_utils.py and engine.py

[ChenyangLi4288]

Issue Link / Problem Description

• Fixes Please do not mute error during transforms #2353

Problem: Errors during testset generation transforms were being silently caught and suppressed

Changes Made

• src/ragas/async_utils.py: Removed exception suppression in process_futures() function (lines 93-95)

  • Previously: Caught all exceptions and converted them to results (result = e)
  • Now: Exceptions propagate naturally to the caller

• src/ragas/testset/transforms/engine.py: Removed exception suppression in run_coroutines() function (line 61)

  • Previously: Caught all exceptions and only logged them (logger.error(...))
  • Now: Exceptions propagate immediately when transforms fail

Why these changes:

• Allows users to see actual error messages (e.g., "temperature not supported") instead of downstream errors
• Follows Python best practices: fail fast and provide clear error messages
• Enables proper debugging of LLM configuration and transform issues

Testing

How to Test

• Automated tests added/updated
• Manual testing steps:
  1. Create a testset generator with an LLM that has invalid configuration (e.g., unsupported temperature value)
  2. Run generator.generate_with_langchain_docs() or apply_transforms()
  3. Verify that the actual error is raised immediately (e.g., BadRequestError: temperature not supported)
  4. Previously: Would see ValueError: Node X has no summary_embedding later in the pipeline
  5. Now: Should see the LLM error immediately when the extractor runs

Example test case (reproduces original issue):

from ragas.testset import TestsetGenerator
from ragas.llms import llm_factory

# Create LLM with invalid temperature for certain models
llm = llm_factory(model="gpt-5-mini", temperature=0.01)  # May not support 0.01

generator = TestsetGenerator(llm=llm)
# This should now raise the actual error immediately instead of failing silently
dataset = generator.generate_with_langchain_docs(documents, testset_size=10)

References

• Related issues: Please do not mute error during transforms #2353
• Root cause: Two layers of exception suppression preventing error propagation
• Impact: Affects all testset generation transforms (extractors, splitters, relationship builders)

[anistark]

Thanks for the attempt @ChenyangLi4288

This however doesn't solve the issue.

Executor class still works as before. Additionally this is creating incompatible exception handling.

run_coroutines is anyway not used.

If you want to take another stab at it, follow the execution path:

apply_transforms() → run_async_tasks() → process_futures() → await future

Also, try not to introduce breaking changes.