Show Web IDE button even if MRs are not available

**Note:**
- Adds feature specs and updates unit tests for this
  so that we can test this at the use case level +
  when the vue file list is fully enabled.

app/views/projects/tree/_tree_header.html.haml

@@ -84,14 +84,13 @@
 
   = render 'projects/find_file_link'
 
-  - if can_create_mr_from_fork
   - if can_collaborate || current_user&.already_forked?(@project)
     - if vue_file_list_enabled?
       #js-tree-web-ide-link.d-inline-block
     - else
       = link_to ide_edit_path(@project, @ref, @path), class: 'btn btn-default qa-web-ide-button' do
         = _('Web IDE')
-    - else
+  - elsif can_create_mr_from_fork
     = link_to '#modal-confirm-fork', class: 'btn btn-default qa-web-ide-button', data: { target: '#modal-confirm-fork', toggle: 'modal'} do
       = _('Web IDE')
     = render 'shared/confirm_fork_modal', fork_path: ide_fork_and_edit_path(@project, @ref, @path)

spec/features/projects/show/user_sees_collaboration_links_spec.rb

@@ -3,14 +3,20 @@
 require 'spec_helper'
 
 describe 'Projects > Show > Collaboration links', :js do
-  let(:project) { create(:project, :repository) }
+  using RSpec::Parameterized::TableSyntax
+
+  let(:project) { create(:project, :repository, :public) }
   let(:user) { create(:user) }
 
   before do
-    project.add_developer(user)
     sign_in(user)
   end
 
+  context 'with developer user' do
+    before do
+      project.add_developer(user)
+    end
+
     it 'shows all the expected links' do
       visit project_path(project)
 
@@ -65,4 +71,28 @@ describe 'Projects > Show > Collaboration links', :js do
 
       expect(page).not_to have_link('Web IDE')
     end
+  end
+
+  context "Web IDE link" do
+    where(:merge_requests_access_level, :user_level, :expect_ide_link) do
+      ::ProjectFeature::DISABLED | :guest | false
+      ::ProjectFeature::DISABLED | :developer | true
+      ::ProjectFeature::PRIVATE | :guest | false
+      ::ProjectFeature::PRIVATE | :developer | true
+      ::ProjectFeature::ENABLED | :guest | true
+      ::ProjectFeature::ENABLED | :developer | true
+    end
+
+    with_them do
+      before do
+        project.project_feature.update!({ merge_requests_access_level: merge_requests_access_level })
+        project.add_user(user, user_level)
+        visit project_path(project)
+      end
+
+      it "updates Web IDE link" do
+        expect(page.has_link?('Web IDE')).to be(expect_ide_link)
+      end
+    end
+  end
 end

spec/views/projects/tree/_tree_header.html.haml_spec.rb

@@ -19,12 +19,12 @@ describe 'projects/tree/_tree_header' do
     allow(view).to receive(:can_collaborate_with_project?) { true }
   end
 
-  it 'does not render the WebIDE button when user cannot create fork or cannot open MR' do
+  it 'renders the WebIDE button when user can collaborate but not create fork or MR' do
     allow(view).to receive(:can?) { false }
 
     render
 
-    expect(rendered).not_to have_link('Web IDE')
+    expect(rendered).to have_link('Web IDE')
   end
 
   it 'renders the WebIDE button when user can create fork and can open MR in project' do
@@ -43,4 +43,13 @@ describe 'projects/tree/_tree_header' do
 
     expect(rendered).to have_link('Web IDE', href: '#modal-confirm-fork')
   end
+
+  it 'does not render the WebIDE button when user cannot collaborate or create mr' do
+    allow(view).to receive(:can?) { false }
+    allow(view).to receive(:can_collaborate_with_project?) { false }
+
+    render
+
+    expect(rendered).not_to have_link('Web IDE')
+  end
 end