Improve changes after MR review.

app/helpers/issuables_helper.rb

@@ -142,7 +142,7 @@ module IssuablesHelper
   end
 
   def cached_assigned_issuables_count(assignee, issuable_type, state)
-    cache_key = "#{assignee.id}_#{issuable_type}_#{state}"
+    cache_key = hexdigest(['assigned_issuables_count', assignee.id, issuable_type, state].join('-'))
     Rails.cache.fetch(cache_key, expires_in: 2.minutes) do
       assigned_issuables_count(assignee, issuable_type, state)
     end
@@ -151,7 +151,7 @@ module IssuablesHelper
   private
 
   def assigned_issuables_count(assignee, issuable_type, state)
-    assignee.send("assigned_#{issuable_type}").send(state).count
+    assignee.public_send("assigned_#{issuable_type}").public_send(state).count
   end
 
   def sidebar_gutter_collapsed?

changelogs/unreleased/fix_navigation_bar_issuables_counters.yml

 ---
 title: Navigation bar issuables counters reflects dashboard issuables counters
-merge_request: 
+merge_request: 7368
 author: Lucas Deschamps

spec/features/dashboard/issuables_counter_spec.rb

@@ -2,7 +2,7 @@ require 'spec_helper'
 
 describe 'Navigation bar counter', feature: true, js: true, caching: true do
   let(:user) { create(:user) }
-  let(:project) { create(:project, namespace: user.namespace) }
+  let(:project) { create(:empty_project, namespace: user.namespace) }
 
   before do
     login_as(user)