Remove languages with low number of translations

Languages with less than 2% of translations will not be available to be
selected.

Refs: https://gitlab.com/gitlab-org/gitlab/-/issues/221012

app/helpers/preferences_helper.rb

@@ -71,7 +71,7 @@ module PreferencesHelper
 
   def language_choices
     options_for_select(
-      Gitlab::I18n::AVAILABLE_LANGUAGES.map(&:reverse).sort,
+      Gitlab::I18n.selectable_locales.map(&:reverse).sort,
       current_user.preferred_language
     )
   end

changelogs/unreleased/kassio-remove-languages-from-ui.yml

+---
+title: Hide languages with few translations
+merge_request: 38312
+author:
+type: changed

doc/development/i18n/externalization.md

@@ -650,6 +650,10 @@ aren't in the message with ID `1 pipeline`.
 
 ## Adding a new language
 
+NOTE: **Note:**
+[Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/221012) in GitLab 13.3:
+Languages with less than 2% of translations won't be available in the UI.
+
 Let's suppose you want to add translations for a new language, let's say French.
 
 1. The first step is to register the new language in `lib/gitlab/i18n.rb`:

lib/gitlab/i18n.rb

@@ -4,6 +4,20 @@ module Gitlab
   module I18n
     extend self
 
+    # Languages with less then 2% of available translations will not
+    # be available in the UI.
+    # https://gitlab.com/gitlab-org/gitlab/-/issues/221012
+    NOT_AVAILABLE_IN_UI = %w[
+      fil_PH
+      pl_PL
+      nl_NL
+      id_ID
+      cs_CZ
+      bg
+      eo
+      gl_ES
+    ].freeze
+
     AVAILABLE_LANGUAGES = {
       'bg' => 'Bulgarian - български',
       'cs_CZ' => 'Czech - čeština',
@@ -29,6 +43,10 @@ module Gitlab
       'zh_TW' => 'Chinese, Traditional (Taiwan) - 繁體中文 (台灣)'
     }.freeze
 
+    def selectable_locales
+      AVAILABLE_LANGUAGES.reject { |key, _value| NOT_AVAILABLE_IN_UI.include? key }
+    end
+
     def available_locales
       AVAILABLE_LANGUAGES.keys
     end

spec/features/profiles/user_edit_preferences_spec.rb

@@ -64,7 +64,7 @@ RSpec.describe 'User edit preferences profile' do
       expect(page).to have_select(
         'user[preferred_language]',
         selected: 'Spanish - español',
-        options: Gitlab::I18n::AVAILABLE_LANGUAGES.values,
+        options: Gitlab::I18n.selectable_locales.values,
         visible: :all
       )
     end

spec/features/profiles/user_visits_profile_preferences_page_spec.rb

@@ -76,13 +76,13 @@ RSpec.describe 'User visits the profile preferences page' do
 
     it 'updates their preference' do
       wait_for_requests
-      select2('eo', from: '#user_preferred_language')
+      select2('pt_BR', from: '#user_preferred_language')
       click_button 'Save'
 
       wait_for_requests
       refresh
 
-      expect(page).to have_css('html[lang="eo"]')
+      expect(page).to have_css('html[lang="pt-BR"]')
     end
   end
 

spec/lib/gitlab/i18n_spec.rb

@@ -5,6 +5,14 @@ require 'spec_helper'
 RSpec.describe Gitlab::I18n do
   let(:user) { create(:user, preferred_language: 'es') }
 
+  describe '.selectable_locales' do
+    it 'does not return languages that should not be available in the UI' do
+      Gitlab::I18n::NOT_AVAILABLE_IN_UI.each do |language|
+        expect(described_class.selectable_locales).not_to include(language)
+      end
+    end
+  end
+
   describe '.locale=' do
     after do
       described_class.use_default_locale