12.3.2 breaking change for CJS consumers — await import('less') requires --experimental-vm-modules in Jest

[gabrielsh2]

Have you used AI?

Yes

Bug Description

less-loader 12.3.2 changed the way less is imported internally from:

const less = require('less');

to:

const less = await import('less');

When the loader is executed via Node.js require(), as Jest does during test runs,
the dynamic ESM import requires the --experimental-vm-modules flag to work.

From what I've checked, these changes were introduced in this PR #578 and it was necessary because of the following less issue less/less.js#4423

The less change was patched in 4.6.3 and then I was able to keep using jest without the ESM flag using 4.6.4 and fixing less-loader into 12.3.1

Link to Minimal Reproduction and step to reproduce

1. Use less-loader 12.3.2 in a CJS project
2. Run Jest tests that involve webpack compilation with the less-loader
3. Observe tests failing without --experimental-vm-modules

Expected Behavior

A change that requires consumers to add Node.js experimental flags should be documented as a breaking change, or released as a major version bump.

Actual Behavior

Released as a patch (12.3.1 → 12.3.2), causing unexpected test failures in CI
for projects that don't use --experimental-vm-modules.

Environment

System:
    OS: macOS 26.3.1
    CPU: (12) arm64 Apple M3 Pro
    Memory: 82.13 MB / 18.00 GB
  Binaries:
    Node: 20.19.2 - /Users/i752731/.nvm/versions/node/v20.19.2/bin/node
    Yarn: 1.22.22 - /Users/i752731/.nvm/versions/node/v20.19.2/bin/yarn
    npm: 10.8.2 - /Users/i752731/.nvm/versions/node/v20.19.2/bin/npm
  Browsers:
    Chrome: 146.0.7680.178
    Firefox: 145.0
    Safari: 26.3.1
  Packages:
    css-loader: ^7.0.0 => 7.1.4 
    html-webpack-plugin: ^5.5.0 => 5.6.6 
    inline-environment-variables-webpack-plugin: ^1.2.1 => 1.2.1 
    less-loader: ^12.3.2 => 12.3.2 
    style-loader: ^4.0.0 => 4.0.0 
    terser-webpack-plugin: ^5.3.14 => 5.4.0 
    webpack: ^5.88.2 => 5.106.0 
    webpack-cli: ^7.0.2 => 7.0.2 
    webpack-merge: ^6.0.0 => 6.0.1 
    webpack-sources: ^3.2.3 => 3.3.4 
    webpack-subresource-integrity: ^5.1.0 => 5.1.0

Is this a regression?

None

Last Working Version

No response

Additional Context

No response