Compatibility with ggplot2 3.6.0

[teunbrand]

Hi there,

Apologies for not posting an issue first.
The ggplot2 package is planning an update for around May 2025 and a reverse dependency test identified a problem with the bayesplot package.
The details are explained in tidyverse/ggplot2#6290, but essentially ggplot2 doesn't populate the plot$labels field before plot building anymore, which violates some test assumptions in this package.

This PR changes the tests to be compatible with both versions of ggplot2.
In addition, some deprecated functionality is avoided.
You can test the changes yourself with the development version of ggplot2 (pak::pak("tidyverse/ggplot2")).
There are some visual changes as well, but I'll leave that up to you to decide wether intervention is needed.

Best,
Teun

[jgabry]

Thanks for the PR!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.62%. Comparing base (20910f5) to head (abfc2ee).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #337      +/-   ##
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+ Coverage   98.51%   98.62%   +0.11%     
==========================================
  Files          35       35              
  Lines        5034     5464     +430     
==========================================
+ Hits         4959     5389     +430     
  Misses         75       75              

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[jgabry]

Like @teunbrand mentioned, there are some visual changes that cause many of the vdiffr tests to fail. I haven't gone through all of them yet (there are a lot) but so far the changes seem small, not requiring intervention. So I'll go ahead and merge this PR and we will update the SVGs for the visual tests once the new version of ggplot2 is released.

[teunbrand]

IIRC many of these changes relate to tidyverse/ggplot2#6071, which can be summarised as that blank ticks no longer reserve space for ticks, which affects the layout. If you really wanted to, you can render the ticks as transparent lines to retain the spacing, but it is a pretty benign change that doesn't ruin plots.

[jgabry]

Thanks for the context. I agree that the change seems benign.