Tools: Ban classnames via Syncpack

[manzoorwanijk]

What?

Adds a Banned version group to syncpack.config.mjs so that any package.json declaring classnames causes npm run lint:deps (and CI) to fail.

Follow-up to #77950 — picks up the isBanned classnames suggestion from @ciampo's review.

Why?

Gutenberg standardised on clsx in #61138 and removed every classnames declaration across the monorepo. There is currently no guardrail preventing it from being re-added later — an npm install classnames --workspace @wordpress/<some-pkg> in any workspace would land silently and bloat bundles with both libraries side by side.

ESLint's no-restricted-imports already catches import classnames from 'classnames' at the source level, but not a stray package.json declaration with no matching import — which is exactly what would happen if someone re-adds the dep ahead of refactoring code. Syncpack catches the declaration; ESLint catches the import. Both layers complement each other.

How?

Single addition to syncpack.config.mjs:

{
    label: 'Banned dependencies that should not be reintroduced.',
    dependencies: [ 'classnames' ],
    packages: [ '**' ],
    isBanned: true,
},

The rule is purely preventive — no current declarations match, so this PR's diff in actual package.json files is empty.

Testing Instructions

# 1. Confirm lint passes on this branch as-is (no current `classnames` declarations):
npm run lint:deps          # exits 0, "✓ No issues found"

# 2. Add `classnames` to any workspace and verify the rule fires:
npm install classnames --workspace @wordpress/components
npm run lint:deps          # exits non-zero; reports `IsBanned`

# 3. `lint:deps:fix` removes the banned declaration:
npm run lint:deps:fix
npm run lint:deps          # exits 0 again

Testing Instructions for Keyboard

N/A — tooling/config only.

Screenshots or screencast

N/A — no UI changes.

Use of AI Tools

Drafted with assistance from Claude Code. The change and PR description were reviewed and edited by hand.

[github-actions]

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Co-authored-by: manzoorwanijk <manzoorwanijk@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[Copilot]

Pull request overview

Adds a Syncpack guardrail to prevent classnames from being reintroduced anywhere in the monorepo via package.json declarations, complementing existing ESLint import restrictions and avoiding duplicate bundle weight alongside clsx.

Changes:

• Add a new versionGroups entry in syncpack.config.mjs marking classnames as banned (isBanned: true) across all packages.

[Mamaduka]

Oh, this is nice!

[github-actions]

Size Change: 0 B

Total Size: 8.44 MB

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[github-actions]

Flaky tests detected in f3cab41.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/27220939432
📝 Reported issues:

• [Flaky Test] should be preserved on first navigation with data-wp-key and attachTo #75767 in /test/e2e/specs/interactivity/router-regions.spec.ts
• [Flaky Test] shows post-locked modal when document size limit is exceeded #78753 in /test/e2e/specs/editor/collaboration/http-only/collaboration-document-size-lock.spec.ts