CSS: ExportType: "style" CSS modules are emitted without __webpack_require__ parameter #22832

Have you used AI?

Yes

Which part of webpack is affected?

css

Bug Description

With native CSS ( experiments.css: true ) and  parser: { exportType: "style" } , the generated module function for a CSS module has no parameters but calls  webpack_require.is(...) :
Example:

(() => {

__webpack_require__.is(1, ".a{color:red}\r\n\n");
}),

A single bundle works only because  webpack_require  happens to be in lexical scope. When the runtime is in a different file from the modules ( optimization.runtimeChunk  plus  splitChunks ), loading the bundle throws:
ReferenceError: __webpack_require__ is not defined

Link to Minimal Reproduction and steps to reproduce

Tested on webpack 5.110.3, 5.111.1 and 5.112.0 (Node 20, Windows). All three fail the same way

1.  npm i webpack webpack-cli
2.  npx webpack 
3. Open  dist/commons.js . The CSS module is  (() => { webpack_require.is(...) }) , with no parameters.
4. Load  runtime.js ,  commons.js ,  main.js  in a browser or  vm  context.  commons.js  throws  ReferenceError: __webpack_require__ is not defined 

** Note: The real-world trigger was Karma with  karma-webpack , which uses a separate  runtime.js  and  commons.js **

Files to recreate issue:
webpack.config.js
entry2.js
entry.js
a.css

Expected Behavior

The module function should receive  __webpack_require__ , as  (__unused_webpack_module, __unused_webpack_exports, __webpack_require__) => {...} , because the generated code uses  RuntimeGlobals.cssInjectStyle  ( __webpack_require__.is ).

Actual Behavior

Loading the bundle throws: ReferenceError: __webpack_require__ is not defined

Environment

• webpack versions: 5.110.3, 5.111.1, 5.112.0 (the bug reproduces on all three)
• Node.js: 20.11.0
• OS: Windows 10/11
• Loaders: none are needed to reproduce. This also happens with  sass-loader  and  postcss-loader  in a real project.

Is this a regression?

Yes (please specify version below)

Last Working Version

5.105

Additional Context

The generated module uses the  cssInjectStyle  runtime global but the module doesn't declare  RuntimeGlobals.require , so the wrapper omits the parameter. This plugin fixes it:

const { RuntimeGlobals } = require("webpack");

class CssStyleRequireFixPlugin {
  apply(compiler) {
    compiler.hooks.thisCompilation.tap("CssStyleRequireFixPlugin", compilation => {
      compilation.hooks.additionalModuleRuntimeRequirements.tap("CssStyleRequireFixPlugin", (module, requirements) => {
        if (module.exportType === "style") requirements.add(RuntimeGlobals.require);
      });
    });
  }
}

In addition, 5.106.0: adds  exportType: "style" , which injects styles at runtime like  style-loader . This is the changelog entry "Add  exportType: "style"  for CSS modules to inject styles into the DOM via HTMLStyleElement, similar to style-loader functionality.