FEATURE: Localization fallbacks (server-side)

[zaibkhan]

No description provided.

[codoki-pr-intelligence]

Codoki PR Review

Summary: Centralize I18n fallbacks, ensure lazy-loading
What’s good: Moves fallback configuration to a single initializer with a clear fallback chain and integrates with the translate accelerator to preload fallback locales.
Review Status: ✅ Safe to merge

Issues (Medium)

Severity	Issue	Why it matters
Medium	Correctness — Potential NoMethodError when default_locale is nil	…/initializers/i18n.rb Calling to_sym on a nil default locale will raise NoMethodError (e.g., during boot or misconfiguration), preventing fallbacks from resolving. Guard the conversion to keep this path safe.
Medium	Maintainability — Order-dependent fallback preload in ensure_loaded!	…/initializers/i18n.rb ensure_loaded! depends on the global I18n.locale; if called before I18n.locale is set in set_locale, it may preload fallbacks for the previous locale and miss the intended one for the current request. Accept an optional locale to remove ordering dependence.

Showing up to 2 medium issue(s). See inline suggestions for more details.

Key Feedback (click to expand)

• Needs improvement: Avoid order dependence on I18n.locale when ensuring fallbacks are loaded and guard against nil default locale to prevent boot-time NoMethodError.
• Testing: Add a controller/request spec verifying the fallback chain order [user locale → site default → en] is honored when a key is missing in the user locale. Include a test for the edge case where SiteSetting.default_locale is temporarily nil (or unset during boot) to ensure no crash and that compact/uniq logic behaves correctly.
• Documentation: Consider a brief comment in the initializer noting that FallbackLocaleList intentionally replaces I18n::Locale::Fallbacks and only needs to respond to #[], plus that ensure_loaded! is required due to on-demand loading in the translate accelerator.
• Compatibility: Overriding I18n.fallbacks with a custom object may affect gems expecting I18n::Locale::Fallbacks; this is likely fine since only #[] is used by I18n::Backend::Fallbacks, but worth noting for future integrations.
• Performance: Fallback preloading runs once per unique locale due to @loaded_locales; negligible overhead after warm-up.
• Open questions: Is SiteSetting.default_locale guaranteed non-nil at boot? In set_locale, is I18n.locale assigned before calling I18n.fallbacks.ensure_loaded!?

Confidence: 4/5 — Looks good; minor fixes (2 medium)

Sequence Diagram

sequenceDiagram
    participant Controller
    participant I18nFallbacks as I18n.fallbacks
    participant I18n
    Controller->>I18nFallbacks: ensure_loaded!()
    I18nFallbacks->>I18n: ensure_loaded!(locale)
    loop each fallback locale
        I18n->>I18n: load_locale(locale)
    end

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[codoki-pr-intelligence]

🔷 Medium: Calling to_sym on a nil default locale will raise NoMethodError (e.g., during boot or misconfiguration), preventing fallbacks from resolving. Guard the conversion to keep this path safe.

Suggested change

	[locale, SiteSetting.default_locale.to_sym, :en].uniq.compact
	[locale, (SiteSetting.default_locale && SiteSetting.default_locale.to_sym), :en].compact.uniq

[codoki-pr-intelligence]

🔷 Medium: ensure_loaded! depends on the global I18n.locale; if called before I18n.locale is set in set_locale, it may preload fallbacks for the previous locale and miss the intended one for the current request. Accept an optional locale to remove ordering dependence.

Suggested change

	def ensure_loaded!
	def ensure_loaded!(locale = I18n.locale)
	self[locale].each { |l| I18n.ensure_loaded! l }
	end