Webpack build never completes when using experimentalUseImportModule

Bug report

Actual Behavior

In the sample project, it hangs indefinitely at 28%.

Expected Behavior

The project should build successfully. In the sample project, it should build successfully with parallelism: 1 and experimentalUseImportModule: true, but it does not.

How Do We Reproduce?

Please see the sample typescript project using css modules - https://github.com/wemyss/webpack-css-mini-extract-plugin-bug. This was the smallest working set of files I could reproduce the issue with (the dependency structure from the entry point is shown below). Note that I had to reduce paralellism from the default of 100 to 1 to demonstrate the issue with such a small project. Instructions to reproduce are in the readme in that repository.

index.ts  -> igloo.ts -> igloo.css -> forest.css -> color.css
         \--------> happy.css --------^

If you set experimentalUseImportModule to false, webpack will successfully generate the build.

Please paste the results of npx webpack-cli info here, and mention other relevant information

System: OS: macOS 11.6.1 CPU: (12) x64 Intel® Core™ i9-8950HK CPU @ 2.90GHz Memory: 1.28 GB / 32.00 GB Binaries: Node: 12.22.5 - /usr/local/bin/node Yarn: 1.22.11 - /usr/local/bin/yarn npm: 6.14.14 - /usr/local/bin/npm Browsers: Chrome: 96.0.4664.110 Firefox: 95.0.1 Safari: 15.1 Safari Technology Preview: 15.4 Packages: css-loader: ^5.2.4 => 5.2.7 ts-loader: ^9.2.3 => 9.2.6 webpack: ^5.54.0 => 5.65.0 webpack-cli: ^4.8.0 => 4.9.1 webpack-dev-server: ^4.6.0 => 4.6.0

[alexander-akait]

You can see this here buildQueue_entries_itemsInProcessingState_debugIds (two modules in progress)

[alexander-akait]

Yep, looks like bug, anyway you don’t need experimentalUseImportModule, because it is enabled by default if webpack is supported it, regarding parallelism, we should fix it