Fix session cleanup

[dreadatour]

Caught an error:

$ python index.py
Exception ignored in atexit callback <function Session._global_cleanup at 0x1058b76a0>:
Traceback (most recent call last):
  File ".../python3.13/site-packages/datachain/query/session.py", line 198, in _global_cleanup
    if isinstance(obj, Session):  # Cleanup temp dataset for session variables.
ReferenceError: weakly-referenced object no longer exists

While running this simplest script:

import datachain as dc

dc.read_storage("s3://bucket/", anon=True).save("dataset")

[Copilot]

Pull Request Overview

This PR enhances session cleanup by catching ReferenceError for finalized objects and logging any other exceptions during global cleanup.

• Wraps obj.__exit__ in a try/except to skip finalized sessions without crashing.
• Logs unexpected errors encountered while cleaning up sessions.

Comments suppressed due to low confidence (1)

src/datachain/query/session.py:197

• Add a test case that simulates a finalized Session object triggering a ReferenceError to verify that this cleanup path is correctly skipped and logged.

for obj in gc.get_objects():  # Get all tracked objects

[Copilot]

Catching all exceptions may hide unexpected errors; consider catching more specific exception types or using logger.exception to preserve the full traceback.

Suggested change

	except Exception as e: # noqa: BLE001
	logger.error(f"Exception while cleaning up session: {e}") # noqa: G004
	except Exception: # noqa: BLE001
	logger.exception("Unexpected exception while cleaning up session.") # noqa: G004

[Copilot]

[nitpick] Consider adding a debug-level log statement here to record when a ReferenceError is caught, which can aid in future troubleshooting.

Suggested change

	except ReferenceError:
	except ReferenceError:
	logger.debug("ReferenceError caught: Object has already been finalized.")

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.

Project coverage is 87.90%. Comparing base (41af6ff) to head (e6809c4).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/datachain/query/session.py	42.85%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1106      +/-   ##
==========================================
- Coverage   87.93%   87.90%   -0.03%     
==========================================
  Files         147      147              
  Lines       12655    12660       +5     
  Branches     1772     1772              
==========================================
+ Hits        11128    11129       +1     
- Misses       1091     1095       +4     
  Partials      436      436              

Flag	Coverage Δ
datachain	87.83% <42.85%> (-0.03%)	⬇️

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