If summary email finds no topics, show topics more than 1 day old from new users

app/mailers/user_notifications.rb

@@ -135,7 +135,11 @@ class UserNotifications < ActionMailer::Base
     end
 
     # Now fetch some topics and posts to show
-    topics_for_digest = Topic.for_digest(user, min_date, limit: SiteSetting.digest_topics + SiteSetting.digest_other_topics, top_order: true).to_a
+    digest_opts = {limit: SiteSetting.digest_topics + SiteSetting.digest_other_topics, top_order: true}
+    topics_for_digest = Topic.for_digest(user, min_date, digest_opts).to_a
+    if topics_for_digest.empty? && !user.user_option.try(:include_tl0_in_digests)
+      topics_for_digest = Topic.for_digest(user, min_date, digest_opts.merge(include_tl0: true)).where('topics.created_at < ?', 24.hours.ago).to_a
+    end
 
     @popular_topics = topics_for_digest[0,SiteSetting.digest_topics]
     @other_new_for_you = topics_for_digest.size > SiteSetting.digest_topics ? topics_for_digest[SiteSetting.digest_topics..-1] : []

app/models/topic.rb

@@ -338,7 +338,7 @@ class Topic < ActiveRecord::Base
               .listable_topics
               .includes(:category)
 
-    unless user.user_option.try(:include_tl0_in_digests)
+    unless opts[:include_tl0] || user.user_option.try(:include_tl0_in_digests)
       topics = topics.where("COALESCE(users.trust_level, 0) > 0")
     end
 

spec/mailers/user_notifications_spec.rb

@@ -152,6 +152,18 @@ describe UserNotifications do
 
     end
 
+    context "with topics only from new users" do
+      let!(:new_today)     { Fabricate(:topic, user: Fabricate(:user, trust_level: TrustLevel[0], created_at: 10.minutes.ago), title: "Hey everyone look at me") }
+      let!(:new_yesterday) { Fabricate(:topic, user: Fabricate(:user, trust_level: TrustLevel[0], created_at: 25.hours.ago), created_at: 25.hours.ago, title: "This topic is of interest to you") }
+
+      it "returns topics from new users if they're more than 24 hours old" do
+        expect(subject.to).to eq([user.email])
+        html = subject.html_part.body.to_s
+        expect(html).to include(new_yesterday.title)
+        expect(html).to_not include(new_today.title)
+      end
+    end
+
     context "with new topics" do
 
       before do

spec/models/topic_spec.rb

@@ -1354,6 +1354,13 @@ describe Topic do
       expect(Topic.for_digest(user, 1.year.ago, top_order: true)).to be_blank
     end
 
+    it "returns topics from TL0 users if given include_tl0" do
+      new_user = Fabricate(:user, trust_level: 0)
+      topic = Fabricate(:topic, user_id: new_user.id)
+
+      expect(Topic.for_digest(user, 1.year.ago, top_order: true, include_tl0: true)).to eq([topic])
+    end
+
     it "returns topics from TL0 users if enabled in preferences" do
       new_user = Fabricate(:user, trust_level: 0)
       topic = Fabricate(:topic, user_id: new_user.id)