Prevent CleanWebpackPlugin webpack plugin from deleting webpack assets

[kasparsd]

Description

Fixes #35980.

How has this been tested?

The updated WP webpack configuration prevents the webpack assets from being deleted in the demo repository according to these GitHub action results.

Screenshots

Types of changes

• Bug fix: prevent the webpack build process from deleting webpack assets from different configurations that are part of the same build task.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[gziolo]

In johnagan/clean-webpack-plugin#122 they recommend using different output folders for individual configs to mitigate the issue.

Doesn't setting cleanStaleWebpackAssets set to false makes the usage of CleanWebpackPlugin obsolete? Would there be still a use case when the old build files get removed before running the build?

[kasparsd]

@gziolo In the example repo I'm already using different output folders for of each webpack config:

const configModern = {
    ...defaultConfig,
    entry: {
        modern: path.join( __dirname, 'js/src/modern.js' ),
    },
    output: {
        path: path.join( __dirname, 'js/dist/modern' ),
    },
};

const configLegacy = {
    ...defaultConfig,
    entry: {
        legacy: path.join( __dirname, 'js/src/legacy.js' ),
    },
    output: {
        path: path.join( __dirname, 'js/dist/legacy' ),
    },
}

The issue is caused by the cleanStaleWebpackAssets implementation which is enabled by default as it assumes that all previous builds (even for different configs) are stale assets and need to be removed.

Doesn't setting cleanStaleWebpackAssets set to false makes the usage of CleanWebpackPlugin obsolete?

My understanding is that cleanOnceBeforeBuildPatterns is the behaviour we want and removing cleanStaleWebpackAssets doesn't impact that.

[gziolo]

I took it for a spin and it works correctly. Let's land this change after rebase. GitHub reports some merge conflicts that need to be resolved manually.

[gziolo]

@kasparsd, can you rebase this PR so we could land it?

[kasparsd]

@gziolo Thanks for the ping! Please let me know if this looks good now.