Fix backwards compatibility in ScalarOp hash

[ricardoV94]

This was detected in #1582 (comment)

It was a very subtle old inconsistency between the default value used in the hash and equality methods of ScalarOps

This fix should be a blocker for the next release.

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📚 Documentation preview 📚: https://pytensor--1616.org.readthedocs.build/en/1616/

[Copilot]

Pull Request Overview

This pull request fixes a backwards compatibility issue in ScalarOp hash calculation. The problem was an inconsistency between the default values used in hash and equality methods, where hash used 0 while equality used None for the output_types_preference attribute. This inconsistency caused C-caching errors when comparing old cached operations with fresh ones.

• Aligns the default value in the __hash__ method to use None instead of 0
• Adds a test to verify hash consistency between old and new ScalarOp instances

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pytensor/scalar/basic.py	Changes default value in __hash__ method from 0 to None
tests/scalar/test_basic.py	Adds test case to verify hash consistency for backwards compatibility

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[ricardoV94]

Note the None default instead of 0 that was used in the hash. That was the issue

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.64%. Comparing base (ee107cb) to head (bfe92a3).
⚠️ Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1616      +/-   ##
==========================================
- Coverage   81.64%   81.64%   -0.01%     
==========================================
  Files         231      231              
  Lines       52998    52997       -1     
  Branches     9395     9395              
==========================================
- Hits        43268    43267       -1     
  Misses       7282     7282              
  Partials     2448     2448              

Files with missing lines	Coverage Δ
pytensor/scalar/basic.py	80.58% <100.00%> (-0.01%)	⬇️

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[jessegrabowski]

Sorry my report of this issue wasn't clearer. But luckily you still tracked it down!

[ricardoV94]

No, it was great that you noticed. This was an ugly one to have missed