Webpack config: Add local name for css module classes for development for easier debugging

[manzoorwanijk]

Currently, when working with CSS modules, the generated class names are base64 hash which are unreadable while debugging. So, it is helpful to have the classnames retained during development.

Slack: p1764235570543949-slack-C05Q5HSS013

Proposed changes:

• Update the global webpack config to update localIdentName for CSS modules for development.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Run jetpack watch plugins/jetpack
• Review some of the pages to ensure they work fine
• Confirm that CSS modules have class name in them
• Run jetpack build plugins/jetpack
• Confirm that the UIs work fine

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack or WordPress.com Site Helper), and enable the add/local-name-for-css-module-classes-for-dev branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack add/local-name-for-css-module-classes-for-dev

bin/jetpack-downloader test jetpack-mu-wpcom-plugin add/local-name-for-css-module-classes-for-dev

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

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[Copilot]

Pull request overview

This PR enhances the webpack configuration for CSS modules to improve developer experience during debugging. It adds a default configuration that retains human-readable local class names in development builds (e.g., button--a1b2c instead of just a1b2c), making it easier to identify and debug CSS module classes in browser DevTools.

Key Changes:

• Adds default CSS modules configuration with auto: true to enable automatic CSS module detection for files with .module.* in their names
• Implements environment-aware localIdentName patterns: readable names in development, hashed names in production

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
projects/js-packages/webpack-config/src/webpack/css-rule.js	Adds default modules configuration with auto-detection and development-friendly class names
projects/js-packages/webpack-config/changelog/add-local-name-for-css-module-classes-for-dev	Documents the enhancement as a patch-level added feature

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[Copilot]

The definition of isDevelopment here is inconsistent with the pattern used elsewhere in the webpack config package. In webpack.js and babel.js, the pattern is to define isProduction first, then derive isDevelopment from it. Consider changing this to match that pattern for consistency.

Suggested change

	const isDevelopment = process.env.NODE_ENV !== 'production';
	const isProduction = process.env.NODE_ENV === 'production';
	const isDevelopment = !isProduction;

[anomiex]

I wouldn't bother with this AI "fix".

[jp-launch-control]

Code Coverage Summary

This PR did not change code coverage!

That could be good or bad, depending on the situation. Everything covered before, and still is? Great! Nothing was covered before? Not so great. 🤷

Full summary · PHP report · JS report

[anomiex]

Looks reasonable, and no noteworthy changes in the build artifacts.