Mixins are not applied for advanced bundled modules

[krzksz]

Preconditions (*)

1. Bundle your JavaScript files using one advanced bundling technique of your choosing, e.g. https://github.com/magento/baler

Steps to reproduce (*)

1. Open the shop.
2. Notice that mixins are neither loaded nor applied for any of the bundled modules.

Expected result (*)

1. Mixins are properly loaded and applied for all modules.

Actual result (*)

1. Mixins are neither loaded nor applied.

Please consult magento/baler#23 where I described the root cause of the issue in great detail. I'm submitting a separate issue here because we believe that it would be best to fix it directly in core and I'm going to send a PR in a few minutes 🤗

[m2-assistant]

Hi @krzksz. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento give me 2.3-develop instance - upcoming 2.3.x release

For more details, please, review the Magento Contributor Assistant documentation.

@krzksz do you confirm that you were able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

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[m2-assistant]

Hi @drpayyne. Thank you for working on this issue.
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