Add missing install instructions for containers

app/graphql/resolvers/ci/runner_setup_resolver.rb

@@ -27,7 +27,7 @@ module Resolvers
         )
 
         {
-          install_instructions: instructions.install_script,
+          install_instructions: instructions.install_script || other_install_instructions(platform),
           register_instructions: instructions.register_command
         }
       ensure
@@ -36,6 +36,10 @@ module Resolvers
 
       private
 
+      def other_install_instructions(platform)
+        Gitlab::Ci::RunnerInstructions::OTHER_ENVIRONMENTS[platform.to_sym][:installation_instructions_url]
+      end
+
       def target_param(args)
         project_param(args[:project_id]) || group_param(args[:group_id]) || {}
       end

spec/graphql/resolvers/ci/runner_setup_resolver_spec.rb

@@ -8,7 +8,24 @@ RSpec.describe Resolvers::Ci::RunnerSetupResolver do
   describe '#resolve' do
     let(:user) { create(:user) }
 
-    subject(:resolve_subject) { resolve(described_class, ctx: { current_user: user }, args: { platform: 'linux', architecture: 'amd64' }.merge(target_param)) }
+    subject(:resolve_subject) { resolve(described_class, ctx: { current_user: user }, args: { platform: platform, architecture: 'amd64' }.merge(target_param)) }
+
+    context 'with container platforms' do
+      let(:platform) { 'docker' }
+      let(:project) { create(:project) }
+      let(:target_param) { { project_id: project.to_global_id } }
+
+      it 'returns install instructions' do
+        expect(resolve_subject[:install_instructions]).not_to eq(nil)
+      end
+
+      it 'does not return register instructions' do
+        expect(resolve_subject[:register_instructions]).to eq(nil)
+      end
+    end
+
+    context 'with regular platforms' do
+      let(:platform) { 'linux' }
 
       context 'without target parameter' do
         let(:target_param) { {} }
@@ -83,4 +100,5 @@ RSpec.describe Resolvers::Ci::RunnerSetupResolver do
         end
       end
     end
+  end
 end