Merge branch '35441-fix-division-by-zero' into 'master'

Fix division by zero for blame age map

Closes #35441

See merge request !13803

3 files changed, 32 insertions, 16 deletions

diff --git a/app/helpers/blame_helper.rb b/app/helpers/blame_helper.rb
index d1dc4d94560..089d9e3e387 100644
--- a/app/helpers/blame_helper.rb
+++ b/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
diff --git a/changelogs/unreleased/35441-fix-division-by-zero.yml b/changelogs/unreleased/35441-fix-division-by-zero.yml
new file mode 100644
index 00000000000..335b2d40494
--- /dev/null
+++ b/changelogs/unreleased/35441-fix-division-by-zero.yml
@@ -0,0 +1,5 @@
+---
+title: Fix division by zero error in blame age mapping
+merge_request: 13803
+author: Jeff Stubler
+type: fixed
diff --git a/spec/helpers/blame_helper_spec.rb b/spec/helpers/blame_helper_spec.rb
index b4368516d83..722d21c566f 100644
--- a/spec/helpers/blame_helper_spec.rb
+++ b/spec/helpers/blame_helper_spec.rb
@@ -35,25 +35,32 @@ describe BlameHelper do
   end
 
   describe '#age_map_class' do
-    let(:dates) do
-      [Time.zone.local(2014, 3, 17, 0, 0, 0)]
-    end
-    let(:blame_groups) do
-      [
-        { commit: double(committed_date: dates[0]) }
-      ]
-    end
+    let(:date) { Time.zone.local(2014, 3, 17, 0, 0, 0) }
+    let(:blame_groups) { [{ commit: double(committed_date: date) }] }
     let(:duration) do
-      project = double(created_at: dates[0])
+      project = double(created_at: date)
       helper.age_map_duration(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'
+      expect(helper.age_map_class(date, duration)).to eq 'blame-commit-age-9'
     end
 
     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
+
+    context 'when called on the same day as project creation' do
+      let(:same_day_duration) do
+        project = double(created_at: now)
+        helper.age_map_duration(today_blame_groups, project)
+      end
+      let(:today_blame_groups) { [{ commit: double(committed_date: now) }] }
+      let(:now) { Time.zone.now }
+
+      it 'returns blame-commit-age-0 class' do
+        expect(helper.age_map_class(duration[:now], same_day_duration)).to eq 'blame-commit-age-0'
+      end
+    end
   end
 end