Pull Request resolves #47755.
Follow-up of #47789

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

This pull request addresses cross-platform path compatibility issues, particularly for Windows environments, by ensuring that module paths consistently use forward slashes in codemirror build.

Cross-platform path handling improvements:

• Updated getPackagesUnderScope in resolve-package.mjs to use forward slashes when constructing module names, avoiding issues with backslashes on Windows that can break Rollup's external module matching.
• Modified asset URI generation in builder.mjs to replace any backslashes with forward slashes, ensuring asset paths are valid in joomla.asset.json.

Testing Instructions

• run npm ci

• apply patch

• run npm ci again

• rename media folder to e. g. media_old

• run npm ci again

Please check if the assets are loading correctly in the backend for the codemirror editor e. g. System -> Site Templates - Open any file. (ref: #47789 (comment))

Issues are currently occurring on Windows, to validate the test results, please specify the operating system on which the tests were executed. The fix for Windows should not cause regressions on other operating systems It would be helpful if we could validate this simultaneously here.

Actual result BEFORE applying this Pull Request

Error during execution on Windows - see #47755

Expected result AFTER applying this Pull Request

should work as expected without errors.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

Thanks @joomdonation!