AO3-6272 Fix chapter count caching 0 after posting draft

app/models/work.rb

@@ -775,9 +775,15 @@ def number_of_chapters
   # Issue 1316: total number needs to reflect the actual number of chapters posted
   # rather than the total number of chapters indicated by user
   def number_of_posted_chapters
-    Rails.cache.fetch(key_for_chapter_posted_counting(self)) do
-      self.chapters.posted.count
-    end
+    Rails.cache.fetch(
+      key_for_chapter_posted_counting(self),
+      skip_nil: true
+    ) do
+      count = chapters.posted.count
+      # Return nil for zero so skip_nil prevents caching stale data.
+      # The .to_i below converts nil back to 0 for callers.
+      count.zero? ? nil : count
+    end.to_i
   end
 
   def chapters_in_order(include_drafts: false, include_content: true)

spec/models/work_spec.rb

@@ -598,4 +598,30 @@
       end
     end
   end
+
+  describe "#number_of_posted_chapters" do
+    it "does not cache a zero count from a stale replica" do
+      work = create(:work)
+      Rails.cache.clear
+
+      stale_relation = double(count: 0)
+      allow(work).to receive(:chapters).and_return(double(posted: stale_relation))
+      work.number_of_posted_chapters
+
+      allow(work).to receive(:chapters).and_call_original
+      expect(work.number_of_posted_chapters).to eq(1)
+    end
+
+    it "caches a non-zero count" do
+      work = create(:work)
+      Rails.cache.clear
+
+      stale_relation = double(count: 3)
+      allow(work).to receive(:chapters).and_return(double(posted: stale_relation))
+      work.number_of_posted_chapters
+
+      allow(work).to receive(:chapters).and_call_original
+      expect(work.number_of_posted_chapters).to eq(3)
+    end
+  end
 end

spec/requests/works_n_plus_one_spec.rb

@@ -3,7 +3,7 @@
 describe "n+1 queries in the WorksController" do
   include LoginMacros
 
-  shared_examples "displaying multiple works efficiently" do
+  shared_examples "displaying multiple works efficiently" do |queries_per_work: nil|
     context "when all works are cached", :n_plus_one do
       populate do |n|
         WorkIndexer.prepare_for_testing
@@ -12,11 +12,20 @@
         subject.call
       end
 
-      it "performs a constant number of queries" do
-        expect do
-          subject.call
-          expect(response.body.scan('<li id="work_').size).to eq(current_scale.to_i)
-        end.to perform_constant_number_of_queries
+      if queries_per_work
+        it "performs #{queries_per_work} query per work" do
+          expect do
+            subject.call
+            expect(response.body.scan('<li id="work_').size).to eq(current_scale.to_i)
+          end.to perform_linear_number_of_queries(slope: queries_per_work)
+        end
+      else
+        it "performs a constant number of queries" do
+          expect do
+            subject.call
+            expect(response.body.scan('<li id="work_').size).to eq(current_scale.to_i)
+          end.to perform_constant_number_of_queries
+        end
       end
     end
 
@@ -140,7 +149,9 @@
     let!(:work_attributes) { { authors: [user.default_pseud], posted: false } }
     let!(:user) { create(:user) }
 
-    it_behaves_like "displaying multiple works efficiently"
+    # Drafts have 0 posted chapters, which we intentionally don't cache
+    # to avoid persisting stale data after posting.
+    it_behaves_like "displaying multiple works efficiently", queries_per_work: 1
   end
 
   describe "#search" do