Notify only when unmergeable due to conflict

There is still the edge case when 'no commits' changes to 'conflict'
would not trigger notification, which we ignore for now.

Calling can_be_merged? can cause exception (e.g. non-UTF8)
Ignore those by rescueing.

Remove unmergeable_reason as now only conflict is notified

Update spec

3 files changed, 15 insertions, 44 deletions

diff --git a/spec/mailers/notify_spec.rb b/spec/mailers/notify_spec.rb
index 775ca4ba0eb..a9a45367b4a 100644
--- a/spec/mailers/notify_spec.rb
+++ b/spec/mailers/notify_spec.rb
@@ -416,16 +416,10 @@ describe Notify do
         end
 
         it 'has the correct subject and body' do
-          reasons = %w[foo bar]
-
-          allow_any_instance_of(MergeRequestPresenter).to receive(:unmergeable_reasons).and_return(reasons)
           aggregate_failures do
             is_expected.to have_referable_subject(merge_request, reply: true)
             is_expected.to have_body_text(project_merge_request_path(project, merge_request))
-            is_expected.to have_body_text('following reasons:')
-            reasons.each do |reason|
-              is_expected.to have_body_text(reason)
-            end
+            is_expected.to have_body_text('due to conflict.')
           end
         end
       end
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 3f028b3bd5c..7ae70c3afb4 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -1324,6 +1324,7 @@ describe MergeRequest do
       context 'when broken' do
         before do
           allow(subject).to receive(:broken?) { true }
+          allow(project.repository).to receive(:can_be_merged?).and_return(false)
         end
 
         it 'becomes unmergeable' do
@@ -2150,9 +2151,11 @@ describe MergeRequest do
       before do
         allow(NotificationService).to receive(:new).and_return(notification_service)
         allow(TodoService).to receive(:new).and_return(todo_service)
+
+        allow(subject.project.repository).to receive(:can_be_merged?).and_return(false)
       end
 
-      it 'notifies, but does not notify again if rechecking still results in cannot_be_merged' do
+      it 'notifies conflict, but does not notify again if rechecking still results in cannot_be_merged' do
         expect(notification_service).to receive(:merge_request_unmergeable).with(subject).once
         expect(todo_service).to receive(:merge_request_became_unmergeable).with(subject).once
 
@@ -2161,7 +2164,7 @@ describe MergeRequest do
         subject.mark_as_unmergeable
       end
 
-      it 'notifies whenever merge request is newly unmergeable' do
+      it 'notifies conflict, whenever newly unmergeable' do
         expect(notification_service).to receive(:merge_request_unmergeable).with(subject).twice
         expect(todo_service).to receive(:merge_request_became_unmergeable).with(subject).twice
 
@@ -2171,6 +2174,15 @@ describe MergeRequest do
         subject.mark_as_unchecked
         subject.mark_as_unmergeable
       end
+
+      it 'does not notify whenever merge request is newly unmergeable due to other reasons' do
+        allow(subject.project.repository).to receive(:can_be_merged?).and_return(true)
+
+        expect(notification_service).not_to receive(:merge_request_unmergeable)
+        expect(todo_service).not_to receive(:merge_request_became_unmergeable)
+
+        subject.mark_as_unmergeable
+      end
     end
 
     describe 'check_state?' do
diff --git a/spec/presenters/merge_request_presenter_spec.rb b/spec/presenters/merge_request_presenter_spec.rb
index d5fb4a7742c..e3b37739e8e 100644
--- a/spec/presenters/merge_request_presenter_spec.rb
+++ b/spec/presenters/merge_request_presenter_spec.rb
@@ -70,41 +70,6 @@ describe MergeRequestPresenter do
     end
   end
 
-  describe "#unmergeable_reasons" do
-    let(:presenter) { described_class.new(resource, current_user: user) }
-
-    before do
-      # Mergeable base state
-      allow(resource).to receive(:has_no_commits?).and_return(false)
-      allow(resource).to receive(:source_branch_exists?).and_return(true)
-      allow(resource).to receive(:target_branch_exists?).and_return(true)
-      allow(resource.project.repository).to receive(:can_be_merged?).and_return(true)
-    end
-
-    it "handles mergeable request" do
-      expect(presenter.unmergeable_reasons).to eq([])
-    end
-
-    it "handles no commit" do
-      allow(resource).to receive(:has_no_commits?).and_return(true)
-
-      expect(presenter.unmergeable_reasons).to eq(["no commits"])
-    end
-
-    it "handles branches missing" do
-      allow(resource).to receive(:source_branch_exists?).and_return(false)
-      allow(resource).to receive(:target_branch_exists?).and_return(false)
-
-      expect(presenter.unmergeable_reasons).to eq(["source branch is missing", "target branch is missing"])
-    end
-
-    it "handles merge conflict" do
-      allow(resource.project.repository).to receive(:can_be_merged?).and_return(false)
-
-      expect(presenter.unmergeable_reasons).to eq(["has merge conflicts"])
-    end
-  end
-
   describe '#conflict_resolution_path' do
     let(:project) { create :project }
     let(:user) { create :user }