Require other in pluralized default translations

[agustinpabon]

What are you adding in this PR?

Add a requireOther option to MatchingTranslations, enabled by default, to report recognized pluralized entries missing other in storefront default locale files.

Fixes #452.

For example, this entry in locales/en.default.json now produces a diagnostic:

{
  "items": {
    "one": "One item"
  }
}

Reports: The pluralized translation 'items' is missing the 'other' key.

Adding an other translation resolves that diagnostic. Setting MatchingTranslations.requireOther: false disables only the new requirement and preserves the existing missing/extra translation checks:

MatchingTranslations:
  requireOther: false

Detection is intentionally conservative: it recognizes non-empty objects whose immediate members are exact plural-category names with string values. Mixed namespaces and non-string structures are not treated as pluralization objects.

The change leaves schema locales and plural-category differences in other languages unchanged. It preserves external namespace exemptions and reports the affected property without inventing translation content or offering an automatic fix.

This intentionally adds a new default-on lint diagnostic. Themes with affected entries may need to add other or disable this requirement.

What's next? Any followup issues?

A Shopify maintainer may need to update the internal shopify.dev documentation for MatchingTranslations to describe requireOther, its default, and its storefront-only scope. That internal documentation update has not been performed in this PR.

Tophatting

For manual verification, use a storefront default locale containing {"items":{"one":"One item"}}. The rule should report the missing other entry. Adding other or setting requireOther: false should remove only that new diagnostic; existing missing/extra translation checks should remain active.

Automated validation

Recorded on Windows with Node 24.19.0 and the checkout's pnpm 10.16.1:

Command	Result
pnpm exec vitest run packages/theme-check-common/src/checks/matching-translations/index.spec.ts on the baseline with the new regression test	18 existing tests passed; regression failed as expected: one diagnostic expected, zero received. The patched rule reports the missing other with the correct file, message and property range.
pnpm exec vitest run packages/theme-check-common/src/checks/matching-translations/index.spec.ts packages/theme-check-node/src/config/load-config.spec.ts	74 tests passed, including 49 rule tests and real YAML-to-production configuration execution.
pnpm exec vitest run packages/theme-check-common packages/theme-check-node	4,994 tests passed across 125 files. This includes the focused tests above; the counts are not additive.
pnpm build	Full workspace build passed, including factory configuration generation and the VS Code extension build.
pnpm type-check	Workspace type checks passed.
pnpm format:check	Source formatting passed.
pnpm exec prettier --check .changeset/plural-translations-require-other.md packages/theme-check-node/configs/all.yml packages/theme-check-node/configs/recommended.yml	Changeset and generated YAML formatting passed.
git diff --check and git diff --check 65fd7743556a6fcb554f08fa58ee13a080a65b07 HEAD	Patch integrity passed.

The full monorepo unit suite, complete platform matrix, browser E2E and live-store integration were not run. Successful local validation was not repeated solely for publication.

Before you deploy

• This PR changes the configuration of a check.
  • Included a minor changeset for @shopify/theme-check-common and @shopify/theme-check-node.
  • Ran pnpm build and committed generated all.yml and recommended.yml updates with requireOther: true.
  • theme-app-extension.yml inherits the recommended configuration; no override is needed.
  • [Shopifolk] Update the internal shopify.dev Theme Check documentation.

AI assistance

OpenAI Codex assisted with implementation and validation. The contributor personally reviewed the diff and diagnostic examples before submission.

[agustinpabon]

I have signed the CLA!