Clean up cohorts table

The cohorts tables is receiving a facelift and the data
provided to the frontend will now exlclude the current
month.

app/services/cohorts_service.rb

@@ -38,7 +38,7 @@ class CohortsService
 
       {
         registration_month: registration_month,
-        activity_months: activity_months,
+        activity_months: activity_months[1..-1],
         total: activity_months.first[:total],
         inactive: inactive
       }

app/views/instance_statistics/cohorts/_cohorts_table.html.haml

+- number_of_data_columns = @cohorts[:months_included] - 1
 .bs-callout.clearfix
   %p
-    User cohorts are shown for the last #{@cohorts[:months_included]}
-    months. Only users with activity are counted in the cohort total; inactive
-    users are counted separately.
+    = s_("Cohorts|User cohorts are shown for the last %{months_included} months. Only users with activity are counted in the 'New users' column; inactive users are counted separately.") % { months_included: @cohorts[:months_included] }
     = link_to icon('question-circle'), help_page_path('user/instance_statistics/user_cohorts', anchor: 'cohorts'), title: 'About this feature', target: '_blank'
 
-.table-holder
+.table-holder.d-xl-table
   %table.table
     %thead
       %tr
-        %th Registration month
-        %th Inactive users
-        %th Cohort total
-        - @cohorts[:months_included].times do |i|
-          %th Month #{i}
+        %th.border-right.pt-4{ colspan: 3 }
+        %th.font-weight-bold.pt-4{ colspan: number_of_data_columns }
+          = s_("Cohorts|Returning users")
+      %tr
+        %th.border-top-0
+          = s_("Cohorts|Registration month")
+        %th.border-top-0
+          = s_("Cohorts|Inactive users")
+        %th.border-top-0.border-right
+          = s_("Cohorts|New users")
+        - number_of_data_columns.times do |i|
+          %th.border-top-0
+            = s_("Cohorts|Month %{month_index}") % { month_index: i + 1 }
     %tbody
       - @cohorts[:cohorts].each do |cohort|
         %tr
           %td= cohort[:registration_month]
           %td= cohort[:inactive]
-          %td= cohort[:total]
+          %td.border-right= cohort[:total]
           - cohort[:activity_months].each do |activity_month|
             %td
               - next if cohort[:total] == '0'

changelogs/unreleased/18668-clean-up-cohorts.yml

+---
+title: Clean up the cohorts table
+merge_request: 20779
+author:
+type: changed

locale/gitlab.pot

@@ -4340,6 +4340,24 @@ msgstr ""
 msgid "Cohorts"
 msgstr ""
 
+msgid "Cohorts|Inactive users"
+msgstr ""
+
+msgid "Cohorts|Month %{month_index}"
+msgstr ""
+
+msgid "Cohorts|New users"
+msgstr ""
+
+msgid "Cohorts|Registration month"
+msgstr ""
+
+msgid "Cohorts|Returning users"
+msgstr ""
+
+msgid "Cohorts|User cohorts are shown for the last %{months_included} months. Only users with activity are counted in the 'New users' column; inactive users are counted separately."
+msgstr ""
+
 msgid "Collapse"
 msgstr ""
 

spec/services/cohorts_service_spec.rb

@@ -22,73 +22,73 @@ describe CohortsService do
       expected_cohorts = [
         {
           registration_month: month_start(11),
-          activity_months: Array.new(12) { { total: 0, percentage: 0 } },
+          activity_months: Array.new(11) { { total: 0, percentage: 0 } },
           total: 0,
           inactive: 0
         },
         {
           registration_month: month_start(10),
-          activity_months: [{ total: 2, percentage: 100 }] + Array.new(10) { { total: 1, percentage: 50 } },
+          activity_months: Array.new(10) { { total: 1, percentage: 50 } },
           total: 2,
           inactive: 0
         },
         {
           registration_month: month_start(9),
-          activity_months: Array.new(10) { { total: 0, percentage: 0 } },
+          activity_months: Array.new(9) { { total: 0, percentage: 0 } },
           total: 0,
           inactive: 0
         },
         {
           registration_month: month_start(8),
-          activity_months: [{ total: 2, percentage: 100 }] + Array.new(8) { { total: 1, percentage: 50 } },
+          activity_months: Array.new(8) { { total: 1, percentage: 50 } },
           total: 2,
           inactive: 0
         },
         {
           registration_month: month_start(7),
-          activity_months: Array.new(8) { { total: 0, percentage: 0 } },
+          activity_months: Array.new(7) { { total: 0, percentage: 0 } },
           total: 0,
           inactive: 0
         },
         {
           registration_month: month_start(6),
-          activity_months: [{ total: 2, percentage: 100 }] + Array.new(6) { { total: 1, percentage: 50 } },
+          activity_months: Array.new(6) { { total: 1, percentage: 50 } },
           total: 2,
           inactive: 0
         },
         {
           registration_month: month_start(5),
-          activity_months: Array.new(6) { { total: 0, percentage: 0 } },
+          activity_months: Array.new(5) { { total: 0, percentage: 0 } },
           total: 0,
           inactive: 0
         },
         {
           registration_month: month_start(4),
-          activity_months: [{ total: 2, percentage: 100 }] + Array.new(4) { { total: 1, percentage: 50 } },
+          activity_months: Array.new(4) { { total: 1, percentage: 50 } },
           total: 2,
           inactive: 0
         },
         {
           registration_month: month_start(3),
-          activity_months: Array.new(4) { { total: 0, percentage: 0 } },
+          activity_months: Array.new(3) { { total: 0, percentage: 0 } },
           total: 0,
           inactive: 0
         },
         {
           registration_month: month_start(2),
-          activity_months: [{ total: 2, percentage: 100 }] + Array.new(2) { { total: 1, percentage: 50 } },
+          activity_months: Array.new(2) { { total: 1, percentage: 50 } },
           total: 2,
           inactive: 0
         },
         {
           registration_month: month_start(1),
-          activity_months: Array.new(2) { { total: 0, percentage: 0 } },
+          activity_months: Array.new(1) { { total: 0, percentage: 0 } },
           total: 0,
           inactive: 0
         },
         {
           registration_month: month_start(0),
-          activity_months: [{ total: 2, percentage: 100 }],
+          activity_months: [],
           total: 2,
           inactive: 1
         }