Fix division by zero for blame age map

app/helpers/blame_helper.rb

@@ -11,11 +11,15 @@ module BlameHelper
   end
 
   def age_map_class(commit_date, duration)
-    commit_date_days_ago = (duration[:now] - commit_date).to_i / 1.day
-    # Numbers 0 to 10 come from this calculation, but only commits on the oldest
-    # day get number 10 (all other numbers can be multiple days), so the range
-    # is normalized to 0-9
-    age_group = [(10 * commit_date_days_ago) / duration[:started_days_ago], 9].min
-    "blame-commit-age-#{age_group}"
+    if duration[:started_days_ago] == 0
+      "blame-commit-age-0"
+    else
+      commit_date_days_ago = (duration[:now] - commit_date).to_i / 1.day
+      # Numbers 0 to 10 come from this calculation, but only commits on the oldest
+      # day get number 10 (all other numbers can be multiple days), so the range
+      # is normalized to 0-9
+      age_group = [(10 * commit_date_days_ago) / duration[:started_days_ago], 9].min
+      "blame-commit-age-#{age_group}"
+    end
   end
 end

changelogs/unreleased/35441-fix-division-by-zero.yml

+---
+title: Fix division by zero error in blame age mapping
+merge_request: 13803
+author: Jeff Stubler
+type: fixed

spec/helpers/blame_helper_spec.rb

@@ -36,17 +36,26 @@ describe BlameHelper do
 
   describe '#age_map_class' do
     let(:dates) do
-      [Time.zone.local(2014, 3, 17, 0, 0, 0)]
+      [Time.zone.local(2014, 3, 17, 0, 0, 0), Time.zone.now]
     end
     let(:blame_groups) do
       [
         { commit: double(committed_date: dates[0]) }
       ]
     end
+    let(:today_blame_groups) do
+      [
+        { commit: double(committed_date: dates[1]) }
+      ]
+    end
     let(:duration) do
       project = double(created_at: dates[0])
       helper.age_map_duration(blame_groups, project)
     end
+    let(:same_day_duration) do
+      project = double(created_at: dates[1])
+      helper.age_map_duration(today_blame_groups, project)
+    end
 
     it 'returns blame-commit-age-9 when oldest' do
       expect(helper.age_map_class(dates[0], duration)).to eq 'blame-commit-age-9'
@@ -55,5 +64,10 @@ describe BlameHelper do
     it 'returns blame-commit-age-0 class when newest' do
       expect(helper.age_map_class(duration[:now], duration)).to eq 'blame-commit-age-0'
     end
+
+    it 'returns blame-commit-age-0 class when created on same day' do
+      puts(same_day_duration.inspect)
+      expect(helper.age_map_class(duration[:now], same_day_duration)).to eq 'blame-commit-age-0'
+    end
   end
 end