FEATURE: Localization fallbacks (server-side)

[ShashankFC]

User description

Test 9

Summary by CodeRabbit

Release Notes

• Refactor

  • Restructured internationalization fallback system with optimized on-demand locale loading for improved efficiency.
  • Enhanced locale fallback resolution to intelligently cascade through requested language, site default, and English.
  • Consolidated locale initialization logic for better maintainability.

• Chore

  • Removed deprecated pluralization backend integration from environment configurations.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

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Replicated from ai-code-review-evaluation/discourse-coderabbit#9

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CodeAnt-AI Description

Server-side localization fallbacks with on-demand locale loading

What Changed

• Adds a custom fallback order so the app shows translations from the user's locale, then the site default, then English when a string is missing
• Loads pluralization and fallback support into the translation backend so plural forms and fallbacks are applied consistently
• Loads locale files on demand and ensures the current user's locale is loaded when setting the locale, reducing missing translation lookups after startup
• Removes redundant environment-level i18n.fallbacks flags that previously had no effect

Impact

✅ Fewer missing translations in the UI
✅ Consistent fallback to site default then English when a translation is absent
✅ Fewer startup-related locale errors

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[ShashankFC]

@CodeAnt-AI: review

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Nitpicks 🔍

🔒 No security issues identified

⚡ Recommended areas for review Possible Nil Error The code calls SiteSetting.default_locale.to_sym without guarding for a nil/blank default_locale. If SiteSetting.default_locale is nil (or not set) this will raise a NoMethodError at runtime. Convert safely before calling to_sym or guard the value. Inconsistent API Usage An ensure_loaded!(locale) helper was added but existing code still calls load_locale(...) unless @loaded_locales.include?(...). Prefer using the new helper everywhere to centralize initialization (it also ensures @loaded_locales is initialized). Also verify thread-safety expectations remain consistent. Potential Performance Impact I18n.fallbacks.ensure_loaded! is invoked on every request in set_locale. That triggers loading of fallback locales (which may load translation files if not already loaded). Even though loading is guarded, this call could still add request overhead; consider limiting when it's necessary or ensure it's effectively no-op after initial load.

[codeant-ai]

Suggestion: Fallback translations are only preloaded when the controller explicitly calls I18n.fallbacks.ensure_loaded!, so in other contexts (e.g. background jobs, rake tasks, or code using I18n.with_locale with a different locale) fallback locales' YAML files are never loaded, causing valid fallback translations to be missed; by loading the fallback locales whenever the fallback list is computed, fallback behavior will work consistently everywhere. [logic error]

Severity Level: Major ⚠️

- ⚠️ Background jobs using I18n miss translations from fallback locales.
- ⚠️ Services using I18n.with_locale bypass controller fallback preloading.
- ⚠️ Inconsistent translations between web and non-controller code.

Suggested change

	[locale, SiteSetting.default_locale.to_sym, :en].uniq.compact
	end
	def ensure_loaded!
	self[I18n.locale].each { |l| I18n.ensure_loaded! l }
	locales = [locale, SiteSetting.default_locale.to_sym, :en].uniq.compact
	locales.each { |l| I18n.ensure_loaded!(l) }
	locales
	end
	def ensure_loaded!(locale = I18n.locale)
	self[locale]

Steps of Reproduction ✅

1. Note the fallback configuration in `config/initializers/i18n.rb:12-23`:
`FallbackLocaleList#[]` only returns `[locale, SiteSetting.default_locale.to_sym,
:en].uniq.compact` without calling `I18n.ensure_loaded!` on any of these locales, and
`ensure_loaded!` explicitly loads fallbacks only for `I18n.locale`.

2. Observe that `ApplicationController#set_locale` in
`app/controllers/application_controller.rb:152-160` is the only place calling
`I18n.fallbacks.ensure_loaded!`, so fallback locales are proactively loaded only for web
requests that pass through this controller filter.

3. Check the lazy-loading implementation in
`lib/freedom_patches/translate_accelerator.rb:45-65`: `I18n.ensure_loaded!(locale)` and
`load_locale` load translations on demand per locale and track them in `@loaded_locales`,
but this is only invoked when some code explicitly calls `I18n.ensure_loaded!(locale)` (or
`I18n.translate` for the current locale), not automatically for fallback locales.

4. In any non-controller context that uses I18n with fallbacks—for example, service/lib
code such as `PostDestroyer.mark_for_deletion` in `lib/post_destroyer.rb:100-109` wrapped
in `I18n.with_locale(SiteSetting.default_locale)` or any background job that calls
`I18n.t` without going through
`ApplicationController#set_locale`—`I18n::Backend::Fallbacks` will consult
`I18n.fallbacks[locale]`, which currently just returns the list of fallback locales
without loading their YAML files; if a translation key exists only in a fallback locale
(e.g., in `:en` but not in the current locale), lookup will fail because that fallback
locale's files were never loaded in this process. The proposed change makes
`FallbackLocaleList#[]` load each locale via `I18n.ensure_loaded!` whenever the fallback
list is computed, so fallback behavior works consistently even in these non-controller
contexts.

Prompt for AI Agent 🤖

This is a comment left during a code review.

**Path:** config/initializers/i18n.rb
**Line:** 17:21
**Comment:**
	*Logic Error: Fallback translations are only preloaded when the controller explicitly calls `I18n.fallbacks.ensure_loaded!`, so in other contexts (e.g. background jobs, rake tasks, or code using `I18n.with_locale` with a different locale) fallback locales' YAML files are never loaded, causing valid fallback translations to be missed; by loading the fallback locales whenever the fallback list is computed, fallback behavior will work consistently everywhere.

Validate the correctness of the flagged issue. If correct, How can I resolve this? If you propose a fix, implement it and please make it concise.

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