Enable new CSS compiler by default

What does this MR do and why?

After analyzing the CSS diff between the new and old compiler, the diff doesn't have us concerned too much. We therefore want to enable the new SASS compiler in CI/CD to see if there are any failures.

Furthermore we turn it on in development by default as well

• See also: #438278 (closed)
• Link to the Diff: gitlab-org/frontend/playground/sass-compiler-diff!1 (comment 1758213709)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

N/A

How to set up and validate locally

1. Restart gdk restart rails-web vite or gdk restart rails-web webpack
2. You should see CSS files compiled in app/assets/builds
3. If you add body{color: red !important} to app/assets/builds/application.css and reload the page, then a few text bits should become red. This "proves" that the new gem cssbundling is used.
4. If you now add body{color: blue !important} to app/assets/stylesheets/application.scss and reload the page, then a few text bits should become blue. This "proves" that vite/webpack started the new CSS compiler.

assigned to @leipert

added frontend maintenancepipelines labels

added typemaintenance label

added 1 commit

• 989c347d - CI: Enable new CSS compiler by default

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Pipeline Changes

This merge request contains changes to the pipeline configuration for the GitLab project.

Please consider the effect of the changes in this merge request on the following:

• Effects on different pipeline types
• Effects on non-canonical projects:
  • gitlab-foss
  • security
  • dev
  • personal forks
• Effects on pipeline performance

Please consider communicating these changes to the broader team following the communication guideline for pipeline changes

Reviewer roulette

Category	Reviewer	Maintainer
backend	@alexbuijs (UTC+1, same timezone as author)	@mbobin (UTC+2, 1 hour ahead of author)
frontend	@elwyn-gitlab (UTC+13, 12 hours ahead of author)	@mlunoe (UTC+1, same timezone as author)
~"Tooling"	Reviewer review is optional for ~"Tooling"	@kushalpandya (UTC+5.5, 4.5 hours ahead of author)
~"Tooling"	Reviewer review is optional for ~"Tooling"	@splattael (UTC+1, same timezone as author)
~"Pipeline configuration"	Reviewer review is optional for ~"Pipeline configuration"	@ddieulivol (UTC+1, same timezone as author)

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changed target branch from master to leipert-make-new-css-compiler-respect-hmr-settings

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• cef14c3e - CI: Enable new CSS compiler by default

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E2E Test Result Summary

allure-report-publisher generated test report!

e2e-test-on-gdk: test report for cb6e4bb9

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Manage      | 0      | 0      | 1       | 0     | 1     | ➖     |
| Data Stores | 2      | 0      | 0       | 0     | 2     | ✅     |
| Package     | 0      | 0      | 1       | 0     | 1     | ➖     |
| Create      | 8      | 0      | 3       | 0     | 11    | ✅     |
| Govern      | 3      | 0      | 0       | 0     | 3     | ✅     |
| Monitor     | 4      | 0      | 0       | 0     | 4     | ✅     |
| Plan        | 4      | 0      | 0       | 0     | 4     | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 21     | 0      | 5       | 0     | 26    | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

e2e-package-and-test: test report for cb6e4bb9

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Manage      | 39     | 0      | 11      | 2     | 50    | ✅     |
| Create      | 148    | 0      | 39      | 4     | 187   | ✅     |
| Govern      | 6      | 0      | 0       | 0     | 6     | ✅     |
| Monitor     | 8      | 0      | 0       | 0     | 8     | ✅     |
| Data Stores | 4      | 0      | 0       | 0     | 4     | ✅     |
| Plan        | 8      | 0      | 0       | 0     | 8     | ✅     |
| Package     | 0      | 0      | 2       | 0     | 2     | ➖     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 213    | 0      | 52      | 6     | 265   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

deleted the leipert-make-new-css-compiler-respect-hmr-settings branch. This merge request now targets the master branch

added 11 commits

• cef14c3e...90b65a33 - 10 commits from branch master
• a13038cd - CI: Enable new CSS compiler by default

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added groupfoundations label

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changed title from CI: Enable new CSS compiler by default to Enable new CSS compiler by default

changed the description

@alexbuijs Could your review backend? Please go with @splattael as a maintainer.

@pgascouvaillancourt Do you have time to review?

cc/ FYI: @peterhegman @svedova @jivanvl @markrian

requested review from @alexbuijs and @pgascouvaillancourt