Fix: Add pickle support for UnwrapFailedError (#2048)

[proboscis]

I have made things!

Checklist

• I have double checked that there are no unrelated changes in this pull request (old patches, accidental config files, etc)
• I have created at least one test case for the changes I have made
• I have updated the documentation for the changes I have made
• I have added my changes to the CHANGELOG.md

Related issues

Fixes #2048

Description

This PR adds pickle support for UnwrapFailedError by implementing the __reduce__ method.
This allows the exception to be serialized/deserialized while preserving the halted_container information when using it in multiprocessing or other scenarios requiring serialization.

Changes

• Added __reduce__ method to UnwrapFailedError class
• Added tests to verify pickling works with both Maybe and Result containers
• Updated CHANGELOG.md under Bugfixes section

[sobolevn]

Thank you for the quick PR!

[sobolevn]

This should be 0.24.1

[sobolevn]

Suggested change

	# Serialize the error
	serialized = pickle.dumps(error)
	# Deserialize
	deserialized_error = pickle.loads(serialized) # noqa: S301
	# Check that halted_container is preserved
	assert deserialized_error.halted_container == Nothing
	assert deserialized_error.halted_container != Some(None)
	# Serialize the error
	serialized = pickle.dumps(error)
	# Deserialize
	deserialized_error = pickle.loads(serialized) # noqa: S301
	# Check that halted_container is preserved
	assert deserialized_error.halted_container == Nothing
	assert deserialized_error.halted_container != Some(None)

[sobolevn]

Please, remove the testing logic from except

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (82ef3ef) to head (d6ff6f7).
Report is 335 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##            master     #2049    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           80        81     +1     
  Lines         2485      2575    +90     
  Branches       437        44   -393     
==========================================
+ Hits          2485      2575    +90     

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[proboscis]

Thank you for the quick review!

[sobolevn]

Suggested change

	error = None
	serialized = None
	error = None
	serialized = None

We only need this var :)

[sobolevn]

Suggested change

assert error is not None

[proboscis]

I apologize that my explanation of the issue was not clear.
Original problem about this pickling issue happend during unpickling time with this error:

TypeError: UnwrapFailedError.__init__() missing 1 required positional argument: 'container'

So my intention was to make sure this UnwrapFailedError is unpicklable by adding __reduce__.

Would keeping the deserialization line be appropriate?

[sobolevn]

Yes, keeping unpickling / pickling is always fine

[proboscis]

I hope the test is now in a good shape?
I also hope i am doing okey since this is my first time making a pr.

[sobolevn]

I also hope i am doing okey since this is my first time making a pr.

Oh wow! Congrats! 🎉
I remember my first PR, it was really fun!

Thank you for you work and for contributing to my project, I really appreciate it :)

[sobolevn]

First PR merged 🎉

[proboscis]

Thank you, I am so happy it got merged! :)
This library has been helping me so much, so thank you for making this great library!