Change public timelines to be filtered by current locale by default (#19291)

In the absence of an opt-in to multiple specific languages in the
preferences, it makes more sense to filter by the user's presumed
language only (interface language or `lang` override)

app/controllers/api/v1/timelines/public_controller.rb

@@ -35,6 +35,7 @@ class Api::V1::Timelines::PublicController < Api::BaseController
   def public_feed
     PublicFeed.new(
       current_account,
+      locale: content_locale,
       local: truthy_param?(:local),
       remote: truthy_param?(:remote),
       only_media: truthy_param?(:only_media)

app/controllers/api/v1/timelines/tag_controller.rb

@@ -36,6 +36,7 @@ class Api::V1::Timelines::TagController < Api::BaseController
     TagFeed.new(
       @tag,
       current_account,
+      locale: content_locale,
       any: params[:any],
       all: params[:all],
       none: params[:none],

app/models/public_feed.rb

@@ -8,6 +8,7 @@ class PublicFeed
   # @option [Boolean] :local
   # @option [Boolean] :remote
   # @option [Boolean] :only_media
+  # @option [String]  :locale
   def initialize(account, options = {})
     @account = account
     @options = options
@@ -27,6 +28,7 @@ class PublicFeed
     scope.merge!(remote_only_scope) if remote_only?
     scope.merge!(account_filters_scope) if account?
     scope.merge!(media_only_scope) if media_only?
+    scope.merge!(language_scope)
 
     scope.cache_ids.to_a_paginated_by_id(limit, max_id: max_id, since_id: since_id, min_id: min_id)
   end
@@ -83,10 +85,19 @@ class PublicFeed
     Status.joins(:media_attachments).group(:id)
   end
 
+  def language_scope
+    if account&.chosen_languages.present?
+      Status.where(language: account.chosen_languages)
+    elsif @options[:locale].present?
+      Status.where(language: @options[:locale])
+    else
+      Status.all
+    end
+  end
+
   def account_filters_scope
     Status.not_excluded_by_account(account).tap do |scope|
       scope.merge!(Status.not_domain_blocked_by_account(account)) unless local_only?
-      scope.merge!(Status.in_chosen_languages(account)) if account.chosen_languages.present?
     end
   end
 end

app/models/status.rb

@@ -95,7 +95,6 @@ class Status < ApplicationRecord
   scope :without_reblogs, -> { where('statuses.reblog_of_id IS NULL') }
   scope :with_public_visibility, -> { where(visibility: :public) }
   scope :tagged_with, ->(tag_ids) { joins(:statuses_tags).where(statuses_tags: { tag_id: tag_ids }) }
-  scope :in_chosen_languages, ->(account) { where(language: nil).or where(language: account.chosen_languages) }
   scope :excluding_silenced_accounts, -> { left_outer_joins(:account).where(accounts: { silenced_at: nil }) }
   scope :including_silenced_accounts, -> { left_outer_joins(:account).where.not(accounts: { silenced_at: nil }) }
   scope :not_excluded_by_account, ->(account) { where.not(account_id: account.excluded_from_timeline_account_ids) }

app/models/tag_feed.rb

@@ -12,6 +12,7 @@ class TagFeed < PublicFeed
   # @option [Boolean] :local
   # @option [Boolean] :remote
   # @option [Boolean] :only_media
+  # @option [String]  :locale
   def initialize(tag, account, options = {})
     @tag = tag
     super(account, options)
@@ -32,6 +33,7 @@ class TagFeed < PublicFeed
     scope.merge!(remote_only_scope) if remote_only?
     scope.merge!(account_filters_scope) if account?
     scope.merge!(media_only_scope) if media_only?
+    scope.merge!(language_scope)
 
     scope.cache_ids.to_a_paginated_by_id(limit, max_id: max_id, since_id: since_id, min_id: min_id)
   end

spec/models/status_spec.rb

@@ -251,22 +251,6 @@ RSpec.describe Status, type: :model do
     end
   end
 
-  describe '.in_chosen_languages' do
-    context 'for accounts with language filters' do
-      let(:user) { Fabricate(:user, chosen_languages: ['en']) }
-
-      it 'does not include statuses in not in chosen languages' do
-        status = Fabricate(:status, language: 'de')
-        expect(Status.in_chosen_languages(user.account)).not_to include status
-      end
-
-      it 'includes status with unknown language' do
-        status = Fabricate(:status, language: nil)
-        expect(Status.in_chosen_languages(user.account)).to include status
-      end
-    end
-  end
-
   describe '.tagged_with' do
     let(:tag1)     { Fabricate(:tag) }
     let(:tag2)     { Fabricate(:tag) }