[Bug]: CSS Modules [hash] can occasionally be zero length if is entirely numeric

[daveskybet]

System Info

System:
OS: macOS 14.6.1
CPU: (10) arm64 Apple M1 Pro
Memory: 454.94 MB / 16.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 20.9.0 - ~/.asdf/installs/nodejs/20.9.0/bin/node
Yarn: 4.4.0 - ~/.asdf/installs/nodejs/20.9.0/bin/yarn
npm: 10.1.0 - ~/.asdf/plugins/nodejs/shims/npm
Watchman: 2024.01.22.00 - /opt/homebrew/bin/watchman
Browsers:
Chrome: 131.0.6778.140
Safari: 17.6
npmPackages:
@rspack/cli: latest => 1.1.6
@rspack/core: latest => 1.1.6

Details

If the hash of a module name/path is entirely numeric the resultant hashed classname has a zero length (due to the removing of numeric characters at the start of the class name), i.e.

generator: {
  localIdentName: "[hash]-[local]",
},

for a module with a path/name of:

./node_modules/@ppb/the-wall-web/components/walls/Badge/Badge.css

results in a completely numeric hash of:

9200104150574146

(default settings of xxhash64/hex/16 - although have also had the same with md4 on a different module)

which due to the existing logic to not have a class name starting with a numeric character will continually remove the first character until the hash has a length of zero, resulting in class names such as:

{
  "badgeComponent": ".-badgeComponent",
  "badgeComponentGameInfo": ".-badgeComponentGameInfo",
  "rouletteNumbers": ".-rouletteNumbers",
  "rouletteNumbersBackground": ".-rouletteNumbersBackground",
}

Webpack currently has a solution for checking for this edge case and providing an alternative hash here:

https://github.com/webpack/webpack/blob/964c0315df0ee86a2b4edfdf621afa19db140d4f/lib/css/CssModulesPlugin.js#L437
https://github.com/webpack/webpack/blob/964c0315df0ee86a2b4edfdf621afa19db140d4f/lib/util/nonNumericOnlyHash.js

Which doesn't appear to have an equivalent in Rspack.

Reproduce link

No response

Reproduce Steps

• Any Rspack app with the localIdentName set to [hash]-[local]
• Have a css module file at a path that results in a completely numeric hash (as per the description ./node_modules/@ppb/the-wall-web/components/walls/Badge/Badge.css results in a completely numeric hash (with the default xxhash64 setting)
• See the output classnames being broken (as the hash is zero length and now starts with a special character)

[inottn]

nonNumericOnlyHash is unrelated to localIdentName. The logic for localIdentName is here. This logic has recently changed, causing rspack to currently be inconsistent with webpack. Simply put, when a class name starts with a digit, webpack prefixes the class name with a '_'.

[daveskybet]

Thanks for the correction @inottn, and seems like a simple enough correction to bring back inline with Webpack so have spun up a PR mentioned above.