Don't use the cache in admin budget stats

In commit e51e03446, we started using the same code to show stats in the
public area and in the admin area. However, in doing so we introduced a
bug, since stats in the public area are only shown after a certain part
of the process has finished, meaning the stats appearing on the page
never change (in theory), so it's perfectly fine to cache them. However,
in the admin area stats can be accessed while the process is still
ongoing, so caching the stats will lead to the wrong results being
displayed.

We've thought about expiring the cache when new supports or ballot lines
are added; however, that means the methods calculating the stats for the
supporting phase would expire when supports are added/removed but the
methods calculating the stats for the voting phase would expire when
ballot lines are added/removed. It gets even more complex because the
`headings` method calculates stats for both the supporting and the
voting phases.

So, since loading stats in the admin section is fast even without the
cache because they only load very basic statistics, we're taking the
simple approach of disabling the cache in this case, so everything works
the same way it did before commit e51e03446.

Co-authored-by: Javi Martín <javim@elretirao.net>

app/components/admin/stats/budget_balloting_component.rb

@@ -8,7 +8,7 @@ class Admin::Stats::BudgetBallotingComponent < ApplicationComponent
   private
 
     def stats
-      @stats ||= Budget::Stats.new(budget)
+      @stats ||= Budget::Stats.new(budget, cache: false)
     end
 
     def headings_stats

app/components/admin/stats/budget_supporting_component.rb

@@ -8,7 +8,7 @@ class Admin::Stats::BudgetSupportingComponent < ApplicationComponent
   private
 
     def stats
-      @stats ||= Budget::Stats.new(budget)
+      @stats ||= Budget::Stats.new(budget, cache: false)
     end
 
     def headings_stats

app/models/concerns/statisticable.rb

@@ -3,7 +3,7 @@ module Statisticable
   PARTICIPATIONS = %w[gender age geozone].freeze
 
   included do
-    attr_reader :resource
+    attr_reader :resource, :cache
   end
 
   class_methods do
@@ -42,8 +42,9 @@ module Statisticable
     end
   end
 
-  def initialize(resource)
+  def initialize(resource, cache: true)
     @resource = resource
+    @cache = cache
   end
 
   def generate
@@ -226,7 +227,11 @@ module Statisticable
       end
     end
 
-    def stats_cache(key, &)
+    def stats_cache(key, &block)
-      Rails.cache.fetch(full_cache_key_for(key), expires_at: Date.current.end_of_day, &)
+      if cache
+        Rails.cache.fetch(full_cache_key_for(key), expires_at: Date.current.end_of_day, &block)
+      else
+        block.call
+      end
     end
 end

spec/models/statisticable_spec.rb

@@ -28,7 +28,8 @@ describe Statisticable do
     stub_const("DummyStats", dummy_stats)
   end
 
-  let(:stats) { DummyStats.new(double(id: 1, class: double(table_name: ""))) }
+  let(:resource) { double(id: 1, class: double(table_name: "")) }
+  let(:stats) { DummyStats.new(resource) }
 
   describe "#gender?" do
     context "No participants" do
@@ -228,8 +229,8 @@ describe Statisticable do
     end
   end
 
-  describe "cache" do
+  describe "cache", :with_cache do
-    it "expires the cache at the end of the day", :with_cache do
+    it "expires the cache at the end of the day by default" do
       time = Time.current
 
       travel_to(time) do
@@ -250,5 +251,20 @@ describe Statisticable do
         expect(stats.total).to eq 7
       end
     end
+
+    it "does not use the cache with cache: false" do
+      stats = DummyStats.new(resource, cache: false)
+      time = Time.current
+
+      travel_to(time) do
+        stats.total = 6
+
+        expect(stats.total).to eq 6
+
+        stats.total = 7
+
+        expect(stats.total).to eq 7
+      end
+    end
   end
 end

spec/system/admin/stats_spec.rb

@@ -99,6 +99,33 @@ describe "Stats", :admin do
         expect(page).to have_link "Go back", count: 1
       end
 
+      scenario "Don't use the cache for supports", :with_cache do
+        budget.update!(phase: :selecting)
+        investment = create(:budget_investment, heading: heading_all_city)
+        create(:user, :level_two, votables: [investment])
+
+        supporter = create(:user, :level_two)
+
+        visit budget_supporting_admin_stats_path(budget_id: budget)
+
+        expect(page).to have_content "VOTES\n1"
+        expect(page).to have_content "PARTICIPANTS\n1"
+
+        in_browser(:supporter) do
+          login_as(supporter)
+
+          visit budget_investment_path(budget, investment)
+          click_button "Support"
+
+          expect(page).to have_button "Remove your support"
+        end
+
+        refresh
+
+        expect(page).to have_content "VOTES\n2"
+        expect(page).to have_content "PARTICIPANTS\n2"
+      end
+
       scenario "hide final voting link" do
         visit admin_stats_path
         click_link "Participatory Budgets"
@@ -135,6 +162,32 @@ describe "Stats", :admin do
         expect(page).to have_content "VOTES\n3"
         expect(page).to have_content "PARTICIPANTS\n2"
       end
+
+      scenario "Don't use the cache for votes", :with_cache do
+        budget.update!(phase: :balloting)
+        create(:user, ballot_lines: [investment])
+
+        balloter = create(:user, :level_two)
+
+        visit budget_balloting_admin_stats_path(budget_id: budget.id)
+
+        expect(page).to have_content "VOTES\n1"
+        expect(page).to have_content "PARTICIPANTS\n1"
+
+        in_browser(:balloter) do
+          login_as(balloter)
+
+          visit budget_investment_path(budget, investment)
+          click_button "Vote"
+
+          expect(page).to have_button "Remove vote"
+        end
+
+        refresh
+
+        expect(page).to have_content "VOTES\n2"
+        expect(page).to have_content "PARTICIPANTS\n2"
+      end
     end
   end