FIX: If result.output is None, return None for all fields

[effigies]

Types of changes

• Bug fix

Summary

Result.output: ty.Optional[ty.Any] = None, but we assume that it's here. In https://github.com/nipype/pydra-tutorial/runs/8254183236, it is possible for it to be None when this is called, so it seems like one sensible thing to do is return None.

That said, it's possible that there's a bigger problem and we should not be trying to retrieve fields without first checking that result.output is not None.

Checklist

• I have added tests to cover my changes (if necessary)
• I have updated documentation (if necessary)

[codecov]

Codecov Report

Base: 77.08% // Head: 76.93% // Decreases project coverage by -0.15% ⚠️

Coverage data is based on head (1740a94) compared to base (86671ad).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #577      +/-   ##
==========================================
- Coverage   77.08%   76.93%   -0.16%     
==========================================
  Files          20       20              
  Lines        4320     4322       +2     
  Branches     1215     1216       +1     
==========================================
- Hits         3330     3325       -5     
- Misses        802      807       +5     
- Partials      188      190       +2     

Flag	Coverage Δ
unittests	76.86% <0.00%> (-0.13%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pydra/engine/specs.py	88.16% <0.00%> (-0.43%)	⬇️
pydra/engine/task.py	85.53% <0.00%> (-1.24%)	⬇️
pydra/engine/core.py	88.73% <0.00%> (-0.31%)	⬇️
pydra/engine/helpers.py	80.14% <0.00%> (+0.23%)	⬆️

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[djarecka]

i think self.output should never be None there... I will try to understand what really went wrong...

[djarecka]

I think #592 should prevent this issue