Merge branch '26155-merge-request-tabs-don-t-render-when-no-commits-available' into 'master'

Resolve "Merge request tabs don't render when no commits available"

Closes #26155 and #24556

See merge request !8347

app/models/merge_request.rb

@@ -221,7 +221,7 @@ class MergeRequest < ActiveRecord::Base
   # true base commit, so we can't simply have `#diff_base_commit` fall back on
   # this method.
   def likely_diff_base_commit
-    first_commit.parent || first_commit
+    first_commit.try(:parent) || first_commit
   end
 
   def diff_start_commit

app/views/projects/merge_requests/_show.html.haml

@@ -50,7 +50,6 @@
     .content-block.content-block-small
       = render 'award_emoji/awards_block', awardable: @merge_request, inline: true
 
-    - if @commits_count.nonzero?
     .merge-request-tabs-holder{ class: ("js-tabs-affix" unless ENV['RAILS_ENV'] == 'test') }
       %div{ class: container_class }
         %ul.merge-request-tabs.nav-links.no-top.no-bottom

app/views/projects/merge_requests/show/_commits.html.haml

-%ol#commits-list.list-unstyled
+- if @commits.empty?
+  .commits-empty
+    %h4
+      There are no commits yet.
+    = custom_icon ('illustration_no_commits')
+- else
+  %ol#commits-list.list-unstyled
     = render "projects/commits/commits", project: @merge_request.source_project, ref: @merge_request.source_branch

app/views/projects/notes/_notes_with_form.html.haml

@@ -23,4 +23,4 @@
           to post a comment
 
 :javascript
-  var notes = new Notes("#{namespace_project_notes_path(namespace_id: @project.namespace, target_id: @noteable.id, target_type: @noteable.class.name.underscore)}", #{@notes.map(&:id).to_json}, #{Time.now.to_i}, "#{diff_view}")
+  var notes = new Notes("#{namespace_project_notes_path(namespace_id: @project.namespace, project_id: @project, target_id: @noteable.id, target_type: @noteable.class.name.underscore)}", #{@notes.map(&:id).to_json}, #{Time.now.to_i}, "#{diff_view}")

changelogs/unreleased/26155-merge-request-tabs-don-t-render-when-no-commits-available.yml

+---
+title: display merge request discussion tab for empty branches
+merge_request: 8347
+author:

spec/features/merge_requests/deleted_source_branch_spec.rb

@@ -4,6 +4,8 @@ require 'spec_helper'
 # message to be shown by JavaScript when the source branch was deleted.
 # Please do not remove "js: true".
 describe 'Deleted source branch', feature: true, js: true do
+  include WaitForAjax
+
   let(:user) { create(:user) }
   let(:merge_request) { create(:merge_request) }
 
@@ -13,7 +15,8 @@ describe 'Deleted source branch', feature: true, js: true do
     merge_request.update!(source_branch: 'this-branch-does-not-exist')
     visit namespace_project_merge_request_path(
       merge_request.project.namespace,
-      merge_request.project, merge_request
+      merge_request.project,
+      merge_request
     )
   end
 
@@ -23,11 +26,17 @@ describe 'Deleted source branch', feature: true, js: true do
     )
   end
 
-  it 'hides Discussion, Commits and Changes tabs' do
+  it 'still contains Discussion, Commits and Changes tabs' do
     within '.merge-request-details' do
-      expect(page).to have_no_content('Discussion')
-      expect(page).to have_no_content('Commits')
-      expect(page).to have_no_content('Changes')
+      expect(page).to have_content('Discussion')
+      expect(page).to have_content('Commits')
+      expect(page).to have_content('Changes')
     end
+
+    click_on 'Changes'
+    wait_for_ajax
+
+    expect(page).to have_selector('.diffs.tab-pane .nothing-here-block')
+    expect(page).to have_content('Nothing to merge from this-branch-does-not-exist into feature')
   end
 end

spec/views/projects/merge_requests/show.html.haml_spec.rb

@@ -7,6 +7,7 @@ describe 'projects/merge_requests/show.html.haml' do
   let(:project) { create(:project) }
   let(:fork_project) { create(:project, forked_from_project: project) }
   let(:unlink_project) { Projects::UnlinkForkService.new(fork_project, user) }
+  let(:note) { create(:note_on_merge_request, project: project, noteable: closed_merge_request) }
 
   let(:closed_merge_request) do
     create(:closed_merge_request,
@@ -19,8 +20,12 @@ describe 'projects/merge_requests/show.html.haml' do
     assign(:project, project)
     assign(:merge_request, closed_merge_request)
     assign(:commits_count, 0)
+    assign(:note, note)
+    assign(:noteable, closed_merge_request)
+    assign(:notes, [])
+    assign(:pipelines, Ci::Pipeline.none)
 
-    allow(view).to receive(:can?).and_return(true)
+    allow(view).to receive_messages(current_user: user, can?: true)
   end
 
   context 'when the merge request is closed' do