[Regression] Use stable sort when prioritizing app assets

[excid3]

This fixes a regression introduced in #206.

sort_by! doesn't preserve the original order so this loses the original order. https://ruby-doc.org/3.3.5/Array.html#method-i-sort_by-21

For duplicates returned by the block, the ordering is indeterminate, and may be unstable.

I ran into this using esbuild and had app/assets/builds as the first entry in paths. After #206, app/javascript always ended up higher priority than app/assets/builds so it was finding the wrong file.

[brenogazzola]

Thanks Chris! I was just talking about this one with a colleague who had this problem. Will just ask him to check and merge if it solves his problem too.

[excid3]

Awesome, thanks for the quick review. It was certainly a head scratcher today as I was testing our Rails 8 migration!

[excid3]

Alternative implementation I considered was to partition into two arrays and re-assign.

config.assets.paths = config.assets.paths.partition { |path| path.to_s.start_with?(Rails.root.to_s) }.flatten

[brenogazzola]

The partition version looks more elegant, though a sort_by! seems more intuitive. Any specific reason you chose one over the other?

[brenogazzola]

Just for future reference, it seems that if all elements of the array are a String, the ordering is not lost. But if you have Pathname variables in there, then the order changes.

[excid3]

I figured partition would allocate a couple arrays and join them back so it is probably slower. Although the arrays probably aren't large enough to matter.

[guilhermeyo]

Thanks!!
The problem was that when reordering, having Pathname also caused the strings to be ordered, which messed up the order. Your change worked perfectly.

[excid3]

Pathname objects seem pretty common because that's what you get from Rails.root.join

The ones causing issues for me are from importmap-rails: https://github.com/rails/importmap-rails/blob/main/lib/importmap/engine.rb#L46-L47

Same approach in most engines/railties I think: https://github.com/rails/mission_control-jobs/blob/main/lib/mission_control/jobs/engine.rb#L93-L94

[brenogazzola]

Yeah, I doubt it will make that much of a difference. But the sort_by is a bit more obvious I think.