fix #1402 , fix #1216

[romainmenke]

Now correctly de-dupes selector lists.

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This minification still feels a bit wonky to me.
Doesn't have sufficient test coverage and it relies on an implementation detail of postcss-selector-parser.

I would personally remove it to prevent bugs.

[codecov-commenter]

Codecov Report

Merging #1403 (4012ea8) into master (4dc2fc5) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1403   +/-   ##
=======================================
  Coverage   97.61%   97.61%           
=======================================
  Files         122      122           
  Lines        9992     9993    +1     
=======================================
+ Hits         9754     9755    +1     
  Misses        238      238           

Impacted Files	Coverage Δ
packages/postcss-minify-selectors/src/index.js	99.23% <100.00%> (+<0.01%)	⬆️

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[ludofischer]

Thank you! It's rare that someone is able to submit a working PR to cssnano. I agree that the code is wonky, but if we deactivated a plugin for that reason we would deactivate most of cssnano. Have you ever looked into swc or Parcel CSS? It looks like they've made a lot of progress building a CSS minifier from scratch, but I don't know if they're less buggy than the current JavaScript CSS minifiers.

[romainmenke]

Thank you! It's rare that someone is able to submit a working PR to cssnano

You're welcome :)
Inner workings here are similar to some things in postcss-preset-env.
So felt right at home

I agree that the code is wonky, but if we deactivated a plugin for that reason we would deactivate most of cssnano. Have you ever looked into swc or Parcel CSS

True, that is the tradeoff with a tool that minifies to equivalent but not equal CSS.
I do like the level of control that is exposed and don't (personally) have a need to switch to swc or parcel.

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Thank you for reviewing and merging this so quickly 🎉