Sourcemaps should be provided for use with minified javascript libraries

[jblz]

Sourcemaps make it possible to debug minified files.

Supported in Chrome:
​https://developers.google.com/chrome-developer-tools/docs/javascript-debugging#source-maps

Landing in Firefox in v23:
​https://wiki.mozilla.org/DevTools/Features/SourceMap

When this feature is enabled, the Chrome console currently shows a 404 when the script specifies a sourcemap file and it isn't found.

[jblz]

jQuery provides a sourcemap:
​http://blog.jquery.com/2013/01/09/jquery-1-9-rc1-and-migrate-rc1-released/#sourcemaps

But since we're customizing it ( see [24791] & #24821 ), we'd need to include our own source & sourcemap files.

[SergeyBiryukov]

Related: #24994

[hakre]

Replying to jblz:

jQuery provides a sourcemap:
​http://blog.jquery.com/2013/01/09/jquery-1-9-rc1-and-migrate-rc1-released/#sourcemaps

But since we're customizing it ( see [24791] & #24821 ), we'd need to include our own source & sourcemap files.

If the sole need of an edit is to add some initialization code after the file has been enqueued, I think it's better to not touch the upstream files but just add the initialization code as data, for example see #25277.

[WraithKenny]

​https://github.com/mishoo/UglifyJS2#source-map-options

​https://github.com/gruntjs/grunt-contrib-uglify#source-maps

The grunt file looks to be using UglifyJS2, which supports source-maps, which means we can just set the proper configuration.

[WraithKenny]

Another option is to delete the sourcemap line out of the comment header at the same time the no conflict line is added, but I really believe that adding the proper source map is a better solution. For that, the removal of the production version should be reverted, and it should be minified as part of the build process, and generate the sourcemap at the same time.

[wonderboymusic]

We should look at our JS in 4.2

[DrewAPicture]

Doesn't seem to be much interest in pursuing this, and no activity here in about a month. Punting.

[swissspidy]

I think we should extend the Grunt tasks to generate source maps when we ship both unminified and minified versions of a library.

[callumbw95]

Hey Everyone,

I've just taken a quick look into this ticket, and I am not sure why this ticket stalled but I believe providing sourcemaps for the minified JavaScript libraries in WP is a massive win for the developer community and is long overdue.

The primary benefit is a modern debugging experience, which is essential for anyone working with WP's JavaScript, from the classic admin to the block editor. This will lower the barrier for new contributors and make it easier for everyone to build on WordPress.

The historical concerns about performance have been fully addressed now that we know that they have zero impact on site performance for end-users, as they are only loaded when developer tools are open.

However digging through the code within the Gruntfile.js it looks like other historical tickets have had an impact on this, as there looks to have been several tickets that have removed this functionality at various points:

• #24994: jquery-1.10.2.min.map 404 error
• #46218: 404 error in source mapping in jquery.form.min.js

As of such I believe we should look into implementing this into the GitHub and SVN versions of the site for developers who are contributing / testing, but I don't believe this is necessary for the production release?

It would be good to get a second opinion here, and as of such I have attached the 2nd-opinion tag. 😃