Fix ref_text of merge request pipelines

Source branch can be removed after the merge and
we have to make sure to avoid rendering links if it's the case.

app/presenters/ci/pipeline_presenter.rb

@@ -63,19 +63,11 @@ module Ci
     end
 
     def link_to_merge_request_source_branch
-      return unless merge_request_presenter
-
-      link_to(merge_request_presenter.source_branch,
-        merge_request_presenter.source_branch_commits_path,
-        class: 'ref-name')
+      merge_request_presenter&.source_branch_link
     end
 
     def link_to_merge_request_target_branch
-      return unless merge_request_presenter
-
-      link_to(merge_request_presenter.target_branch,
-        merge_request_presenter.target_branch_commits_path,
-        class: 'ref-name')
+      merge_request_presenter&.target_branch_link
     end
 
     private

app/presenters/merge_request_presenter.rb

@@ -216,6 +216,22 @@ class MergeRequestPresenter < Gitlab::View::Presenter::Delegated
     help_page_path('ci/merge_request_pipelines/index.md')
   end
 
+  def source_branch_link
+    if source_branch_exists?
+      link_to(source_branch, source_branch_commits_path, class: 'ref-name')
+    else
+      content_tag(:span, source_branch, class: 'ref-name')
+    end
+  end
+
+  def target_branch_link
+    if target_branch_exists?
+      link_to(target_branch, target_branch_commits_path, class: 'ref-name')
+    else
+      content_tag(:span, target_branch, class: 'ref-name')
+    end
+  end
+
   private
 
   def cached_can_be_reverted?

changelogs/unreleased/fix-ref-text-of-mr-pipelines.yml

@@ -0,0 +1,6 @@
+---
+title: Fix pipelines for merge requests does not show pipeline page when source branch
+  is removed
+merge_request: 27803
+author:
+type: fixed

spec/features/projects/pipelines/pipeline_spec.rb

@@ -331,11 +331,9 @@ describe 'Pipeline', :js do
         merge_request.all_pipelines.last
       end
 
-      before do
-        visit_pipeline
-      end
-
       it 'shows the pipeline information' do
+        visit_pipeline
+
         within '.pipeline-info' do
           expect(page).to have_content("#{pipeline.statuses.count} jobs " \
                                        "for !#{merge_request.iid} " \
@@ -347,6 +345,21 @@ describe 'Pipeline', :js do
         end
       end
 
+      context 'when source branch does not exist' do
+        before do
+          project.repository.rm_branch(user, merge_request.source_branch)
+        end
+
+        it 'does not link to the source branch commit path' do
+          visit_pipeline
+
+          within '.pipeline-info' do
+            expect(page).not_to have_link(merge_request.source_branch)
+            expect(page).to have_content(merge_request.source_branch)
+          end
+        end
+      end
+
       context 'when source project is a forked project' do
         let(:source_project) { fork_project(project, user, repository: true) }
 
@@ -386,11 +399,11 @@ describe 'Pipeline', :js do
 
       before do
         pipeline.update(user: user)
-
-        visit_pipeline
       end
 
       it 'shows the pipeline information' do
+        visit_pipeline
+
         within '.pipeline-info' do
           expect(page).to have_content("#{pipeline.statuses.count} jobs " \
                                        "for !#{merge_request.iid} " \
@@ -405,6 +418,21 @@ describe 'Pipeline', :js do
         end
       end
 
+      context 'when target branch does not exist' do
+        before do
+          project.repository.rm_branch(user, merge_request.target_branch)
+        end
+
+        it 'does not link to the target branch commit path' do
+          visit_pipeline
+
+          within '.pipeline-info' do
+            expect(page).not_to have_link(merge_request.target_branch)
+            expect(page).to have_content(merge_request.target_branch)
+          end
+        end
+      end
+
       context 'when source project is a forked project' do
         let(:source_project) { fork_project(project, user, repository: true) }
 

spec/presenters/merge_request_presenter_spec.rb

@@ -439,6 +439,52 @@ describe MergeRequestPresenter do
     end
   end
 
+  describe '#source_branch_link' do
+    subject { presenter.source_branch_link }
+
+    let(:presenter) { described_class.new(resource, current_user: user) }
+
+    context 'when source branch exists' do
+      it 'returns link' do
+        allow(resource).to receive(:source_branch_exists?) { true }
+
+        is_expected
+          .to eq("<a class=\"ref-name\" href=\"#{presenter.source_branch_commits_path}\">#{presenter.source_branch}</a>")
+      end
+    end
+
+    context 'when source branch does not exist' do
+      it 'returns text' do
+        allow(resource).to receive(:source_branch_exists?) { false }
+
+        is_expected.to eq("<span class=\"ref-name\">#{presenter.source_branch}</span>")
+      end
+    end
+  end
+
+  describe '#target_branch_link' do
+    subject { presenter.target_branch_link }
+
+    let(:presenter) { described_class.new(resource, current_user: user) }
+
+    context 'when target branch exists' do
+      it 'returns link' do
+        allow(resource).to receive(:target_branch_exists?) { true }
+
+        is_expected
+          .to eq("<a class=\"ref-name\" href=\"#{presenter.target_branch_commits_path}\">#{presenter.target_branch}</a>")
+      end
+    end
+
+    context 'when target branch does not exist' do
+      it 'returns text' do
+        allow(resource).to receive(:target_branch_exists?) { false }
+
+        is_expected.to eq("<span class=\"ref-name\">#{presenter.target_branch}</span>")
+      end
+    end
+  end
+
   describe '#source_branch_with_namespace_link' do
     subject do
       described_class.new(resource, current_user: user).source_branch_with_namespace_link