• Operating System: MacOS 10.15.5 (19F101)
• Node Version: v14.4.0
• NPM Version: N/A (Yarn 1.22.4)
• webpack Version: webpack@4.43.0
• copy-webpack-plugin Version: 6.x

Expected Behavior

Files should be transformed/copied only once per build

Actual Behavior

In 5.x the files are transformed once per build (verified by logging when transform is called). In 6.x the transform function is called a large number of times (perhaps 6-10 times per file.

I noticed that removing new VueLoaderPlugin() from the plugins list reduced the multiple calls down to two per file. My suspicion is that in 6.x you're hooking into an event that runs even on child builds rather than on the entry point build. new VueLoaderPlugin() seems to kick off a lot of child builds depending on the number of Vue components in the application.

Reverting to 5.x fixed the issue.

Code

// webpack.config.js

...
transform(content, filePath) {
  console.log(filePath)
}
...

new VueLoaderPlugin()

How Do We Reproduce?

The only hint I have is to do with new VueLoaderPlugin(). Hopefully this is enough of a pointer, but if not, let me know and I'll look into creating a minimal reproducible.