Drupal core contains some 3rd party javascript libraries, among them jQuery. Typically such libraries are available as un-minified and minified versions. A minified js file can have a reference to a source map via sourceMappingURL, which can be used by the browser developer tools to show the original source.

Since https://www.drupal.org/project/drupal/issues/1341792, js files like jQuery are shipped as a minified version.

In https://www.drupal.org/project/devel/issues/2471919, it was considered to add an option in devel to send the un-minified version instead. This was discarded because we can use source maps.

The minified jQuery.min.js used to have a sourceMappingURL reference, but this is gone in newer versions.

I also found some issues talking about warnings and errors from files with sourceMappingURL, if the referenced source map is missing. But I don't know if these are related.


There seems to be no way (besides hackery) to see the original js file (e.g. original jQuery.js) for debugging in the browser.

EDIT: The browser can prettify the js, but it cannot un-minify the variable names or restore comments. So I do not consider this a sufficient solution. I should have mentioned this directly.


Am I missing something? Is there a hidden option or contrib solution to make the source maps work, or to use the un-minified jquery.js for debugging during development?

(depending on the answer, I might open an issue on drupal.org)



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