Bugfix/swi 63 handle empty policy area

[Tschuppi81]

SWI: Ignore empty policy area

TYPE: Bugfix
LINK: swi-63

Checklist

• I have performed a self-review of my code
• I considered adding a reviewer
• I have tested my code thoroughly by hand
• I have added tests for my changes/features

[Tschuppi81]

Is there a way to influence the converters to handle this case?

[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.41%. Comparing base (444995f) to head (ddc3461).
⚠️ Report is 164 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/onegov/core/filters.py	81.81%	2 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/onegov/swissvotes/collections/votes.py	98.92% <100.00%> (+<0.01%)	⬆️
src/onegov/swissvotes/converters.py	100.00% <100.00%> (ø)
src/onegov/swissvotes/path.py	97.82% <100.00%> (+0.04%)	⬆️
src/onegov/core/filters.py	86.95% <81.81%> (-3.96%)	⬇️

... and 2 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 444995f...ddc3461. Read the comment docs.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Daverball]

Is there a way to influence the converters to handle this case?

Yes, you can write a custom converter for the policy area format, so any values that don't conform to the format get dropped.

Ideally we change the collection to accept list[PolicyArea] instead and write a converter for PolicyArea that verifies the format, split the string over . and make sure each component is numeric and starts with the previous component.

[Daverball]

This is closer to what I suggested, but it's not quite there yet.

[Daverball]

I think you should merge master, this looks like changes that happened a while ago on master, so they should not be included in the diff.

[Daverball]

This check should go away if the converter is doing its job

[Daverball]

This seems a little bit too complex for a converter, I would choose two simple converter functions like we do for things like datetime_converter and use the base class. Converter decode functions are allowed to raise exceptions IIRC, but you could also add simple try catch that returns None if splitting the components and turning them into integers fails.

The other issue is that you're converting from str to str. My idea was to convert to PolicyArea and move some of the validation into the PolicyArea constructor, this makes the API less error-prone to use in general, since the collection will now expect a PolicyArea instance rather than str, which has already been validated, with str it's still possible to pass in bogus data from somewhere else.

[Daverball]

I'm also not sure if this will actually work, since Converter.__init__ will replace your decode/encode methods with whatever you passed in when constructing the instance, which is str.