[Bug] virtual module trigger extra compilation in webpack 5

• I’d be willing to submit the fix

Describe the bug

Using the latest webpack 5 and the latest webpack-virtual-modules. I notice that webpack is logging out 2 compilation in watch mode.

To Reproduce

Run webpack --watch to reproduce using this brranch: https://github.com/michenly/webpack-5-demo/tree/webpack-virtual-modules-error

Minimally, use webpack-virtual-modules (I did this in both in a plugin with .apply and in webpack config’s plugin directly with the same result)

new VirtualModulesPlugin({'test.js': `export default 'test123'`})

Log out compilation message by tapping into compiler.hooks.compile and see two compilation message as soon as webpack --watch is run

Screenshots

Environment if relevant (please complete the following information):

• OS: OSX 11.15.1
• Node version: v12.14.0
• Mochapack version: ?
• Webpack version: 5.50.0
• webpack-virtual-modules version: 0.4.3

Additional context

I also log out complier.removedFiles in compiler.hooks.watchRun, notice how the virtual module is listed as files that was removed.

[andy0130tw]

@larixer Sure. I have opened a PR.

[andy0130tw]

Update: I have worked out a more robust, Proxy-based solution that treats the original WatchFileSystem as an abstract object. Should be more resilient to breaking changes in Webpack and Watchpack.

Code: https://github.com/andy0130tw/webpack-virtual-modules/blob/24d823f3133da9f397224cdfedd39be341546b21/src/wfs.ts