Bugfix issue 3230

[jonascristens]

Dear @mwaskom,

I would love to contribute to the amazing project, so I have tried to resolve issue 3230.

Issue: The kws dict contained a list of tuples of dashes instead of single tuple for plotting.
Solution: Revert code partially back to changes made here
Prevention: add an additional test to check for the existing issue

[mwaskom]

Thanks for taking a crack at this bug. It looks like you've run black over the files you've modified, which makes it very difficult to assess the functional changes to the code. Can you please revert the stylistic changes so the diff just reflects the bugfix? Thanks!

[jonascristens]

The black changes have been reversed, thanks for the quick feedback!

[mwaskom]

Thanks but I don't think this is the right solution. Better to handle the bug where it was introduced, in the process of reconciling parameters in the body of lineplot. I am pretty sure that you just need to change this line:

https://github.com/mwaskom/seaborn/blob/master/seaborn/relational.py#L599

There are two ways to have a defined style mapping: explicitly, where the local style variable is not None, and implicitly, when using wide-form data. The change added here to allow dashes to be a literal specification of dashes when not using a style mapping forgot about the second (implicit) way. So basically I think this just needs to change the check for style is None to "style" not in p.variables.

[jonascristens]

Thanks for the feedback, I've adjusted the code as requested. I now have a better understanding of what is happening exactly.

[codecov]

Codecov Report

Merging #3316 (65f708c) into master (4f72554) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3316   +/-   ##
=======================================
  Coverage   98.38%   98.38%           
=======================================
  Files          77       77           
  Lines       24942    24955   +13     
=======================================
+ Hits        24538    24551   +13     
  Misses        404      404           

Impacted Files	Coverage Δ
seaborn/relational.py	99.68% <100.00%> (ø)
tests/test_relational.py	99.31% <100.00%> (+<0.01%)	⬆️

... and 2 files with indirect coverage changes

[mwaskom]

Thanks!