CssModule context property is null in v0.8.1

[i-like-robots]

• Operating System: Mac OS 10.14
• Node Version: 10.14
• NPM Version: 6.4.1
• webpack Version: 4.41.2
• mini-css-extract-plugin Version: 0.8.1

Expected Behavior

We have implemented code splitting in our apps which uses each module's context property to decide whether they should be extracted into separate chunk. We have used this configuration for some time but has broken when using v0.8.1 of this package.

Actual Behavior

The context property for instances of CssModule is null instead of a string as we expect so our Webpack compilation fails. e.g.:

(module) => module.context.includes('foo') // TypeError: Cannot read property 'includes' of null

Code

Here is an example configuration for enabling code splitting using module.context:

// webpack.config.js
module.exports = {
  optimization: {
    splitChunks: {
      cacheGroups: {
        vendors: {
          test (module) {
            return module.context.includes('dom-loaded')
          }
        }
      }
    }
  }
}

How Do We Reproduce?

Try adding the code splitting configuration shown above to a project using this plugin and a CSS entry point (or try any configuration which expects module.context to be a string).

EDIT: test repo here https://github.com/i-like-robots/broken-css-extract-plugin

[alexander-akait]

We don't touch this code in 0.8.1, please create reproducible test repo

[i-like-robots]

Here you go: https://github.com/i-like-robots/broken-css-extract-plugin

If you run npx webpack or npm run build it should fail.

Install v0.8.0 of this plugin (npm i mini-css-extract-plugin@0.8.0) and run the Webpack build again and it should pass.

Hope that helps!

[alexander-akait]

@i-like-robots what about return module.context && module.context.includes('dom-loaded')?

[i-like-robots]

We can do that but I'm concerned that a public part of this module's interface has changed unexpectedly. I assume this may cause other users a problem as well 😱

[i-like-robots]

Thank you @evilebottnawi - much appreciated 🙇