[Bug]: % symbol getting stripped from zero on percentage-only values

[Yurickh]

Describe the bug

The % symbol is getting stripped from zero values on rules where unitless values are not supported, causing those rules to break.

Expected behaviour

Expected that when running cssnano on the following piece of css:

.potato {
  background-color: color-mix(#000, #FFF 0%);
}

it wouldn't remove the % sign, as that invalidates the color rule.

Steps to reproduce

1. Clone my repo at https://github.com/Yurickh/cssnano-issue-repro
2. Run npm install && npm run minify
3. Verify that the output.css file doesn't have a % sign.

Version

6 and 7

Preset

default

Environment

System:
    OS: macOS 14.4.1
    CPU: (12) arm64 Apple M2 Pro
    Memory: 4.57 GB / 32.00 GB
    Shell: 5.9 - /bin/zsh

Package details

cssnano-issue-repro@1.0.0 /Users/YHAUSCHI/github/oss/cssnano-issue-repro
├─┬ cssnano@7.0.1
│ ├─┬ cssnano-preset-default@7.0.1
│ │ ├─┬ css-declaration-sorter@7.2.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ cssnano-utils@5.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-calc@10.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-colormin@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-convert-values@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-discard-comments@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-discard-duplicates@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-discard-empty@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-discard-overridden@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-merge-longhand@7.0.0
│ │ │ ├── postcss@8.4.38 deduped
│ │ │ └─┬ stylehacks@7.0.0
│ │ │   └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-merge-rules@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-minify-font-values@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-minify-gradients@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-minify-params@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-minify-selectors@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-charset@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-display-values@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-positions@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-repeat-style@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-string@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-timing-functions@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-unicode@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-url@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-normalize-whitespace@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-ordered-values@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-reduce-initial@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-reduce-transforms@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-svgo@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ ├─┬ postcss-unique-selectors@7.0.0
│ │ │ └── postcss@8.4.38 deduped
│ │ └── postcss@8.4.38 deduped
│ └── postcss@8.4.38 deduped
├─┬ postcss-cli@11.0.0
│ ├─┬ postcss-load-config@5.1.0
│ │ └── postcss@8.4.38 deduped
│ ├─┬ postcss-reporter@7.1.0
│ │ └── postcss@8.4.38 deduped
│ └── postcss@8.4.38 deduped
└── postcss@8.4.38

Additional context

No response

[pgregorova]

I have been experiencing similar issue on a project where no matter how I enter the values for box-shadow, whether it is:
rgba(255,255,255,.7) 0 0 0 4000px inset or #ffffffb8 0 0 0 4000px inset
the output always ends up as:
inset 0 0 0 250pc hsla(0,0,100%,.7215686275) instead of
inset 0 0 0 250pc hsla(0,0%,100%,.7215686275), which makes it invalid as it is omitting % from the second 0

[ludofischer]

I have been experiencing similar issue on a project where no matter how I enter the values for box-shadow, whether it is: rgba(255,255,255,.7) 0 0 0 4000px inset or #ffffffb8 0 0 0 4000px inset the output always ends up as: inset 0 0 0 250pc hsla(0,0,100%,.7215686275) instead of inset 0 0 0 250pc hsla(0,0%,100%,.7215686275), which makes it invalid as it is omitting % from the second 0

I cannot reproduce your issue. It seems to work on the Playground too? https://cssnano.github.io/cssnano/playground/ Have you got any more details like the preset and maybe Browserslist configuration>