Add Pages public folder check

Throw an InvalidStateError
if there is no public
folder present inside
a pages build artifact

Changelog: other

app/services/projects/update_pages_service.rb

@@ -30,6 +30,7 @@ module Projects
       validate_state!
       validate_max_size!
+      validate_public_folder!
       validate_max_entries!
       build.artifacts_file.use_file do |artifacts_path|
@@ -180,6 +181,10 @@ module Projects
       end
     end
+    def validate_public_folder!
+      raise InvalidStateError, 'Error: The `public/` folder is missing, or not declared in `.gitlab-ci.yml`.' unless total_size > 0
+    end
+
     def entries_count
       # we're using the full archive and pages daemon needs to read it
       # so we want the total count from entries, not only "public/" directory

spec/services/projects/update_pages_service_spec.rb

@@ -13,6 +13,7 @@ RSpec.describe Projects::UpdatePagesService do
   let(:file) { fixture_file_upload("spec/fixtures/pages.zip") }
   let(:empty_file) { fixture_file_upload("spec/fixtures/pages_empty.zip") }
+  let(:empty_metadata_filename) { "spec/fixtures/pages_empty.zip.meta" }
   let(:metadata_filename) { "spec/fixtures/pages.zip.meta" }
   let(:metadata) { fixture_file_upload(metadata_filename) if File.exist?(metadata_filename) }
@@ -91,6 +92,17 @@ RSpec.describe Projects::UpdatePagesService do
         end
       end
+      context 'when archive does not have pages directory' do
+        let(:file) { empty_file }
+        let(:metadata_filename) { empty_metadata_filename }
+
+        it 'returns an error' do
+          expect(execute).not_to eq(:success)
+
+          expect(GenericCommitStatus.last.description).to eq("Error: The `public/` folder is missing, or not declared in `.gitlab-ci.yml`.")
+        end
+      end
+
       it 'limits pages size' do
         stub_application_setting(max_pages_size: 1)
         expect(execute).not_to eq(:success)