Adjust install generator for typescript setups

lib/generators/inertia/install/install_generator.rb

@@ -182,6 +182,7 @@ def install_vite
               exit(false)
             end
             if (capture = run('bundle exec vite install', capture: !verbose?))
+              rename_application_js_to_ts if typescript?
               say 'Vite Rails successfully installed', :green
             else
               say capture
@@ -192,6 +193,13 @@ def install_vite
         end
       end
 
+      def rename_application_js_to_ts
+        return unless File.exist?(application_js_path) && application_layout.read.include?("<%= vite_javascript_tag 'application' %>")
+
+        FileUtils.mv(application_js_path, application_ts_path)
+        gsub_file application_layout.to_s, /<%= vite_javascript_tag 'application' %>/, "<%= vite_typescript_tag 'application' %>"
+      end
+
       def ruby_vite_installed?
         return true if package_manager.present? && ruby_vite?
 
@@ -253,6 +261,14 @@ def typescript?
         @typescript = options[:typescript] || yes?('Would you like to use TypeScript? (y/n)', :green)
       end
 
+      def application_js_path
+        js_file_path('entrypoints/application.js')
+      end
+
+      def application_ts_path
+        js_file_path('entrypoints/application.ts')
+      end
+
       def inertia_entrypoint
         "inertia.#{typescript? ? 'ts' : 'js'}"
       end

spec/generators/install/install_generator_spec.rb

@@ -35,6 +35,22 @@
     end
   end
 
+  shared_context 'assert application.js entrypoint renaming' do
+    let(:typescript_enabled?) { args.include?('--typescript') }
+
+    it 'renames application.js to application.ts if TypeScript flag is enabled' do
+      expect { generator }.not_to raise_error
+
+      if typescript_enabled?
+        expect(File.exist?(File.join(destination_root, 'app/frontend/entrypoints/application.ts'))).to be true
+        expect(File.exist?(File.join(destination_root, 'app/frontend/entrypoints/application.js'))).to be false
+      else
+        expect(File.exist?(File.join(destination_root, 'app/frontend/entrypoints/application.js'))).to be true
+        expect(File.exist?(File.join(destination_root, 'app/frontend/entrypoints/application.ts'))).to be false
+      end
+    end
+  end
+
   context 'without vite' do
     before do
       prepare_application(with_vite: false)
@@ -57,6 +73,14 @@
           end
         end)
       end
+
+      include_context 'assert application.js entrypoint renaming'
+
+      context 'with --typescript' do
+        let(:args) { super() + %w[--typescript] }
+
+        include_context 'assert application.js entrypoint renaming'
+      end
     end
   end
 
@@ -192,7 +216,7 @@ def expect_packages_for(framework, ext: 'js')
     end)
   end
 
-  def expect_inertia_prepared_for(framework, ext: 'js')
+  def expect_inertia_prepared_for(framework, ext: 'js', application_js_exists: false)
     expect(destination_root).to(have_structure do
       case framework
       when :react
@@ -230,10 +254,15 @@ def expect_inertia_prepared_for(framework, ext: 'js')
         end
       end
       file('app/views/layouts/application.html.erb') do
-        if ext == 'ts'
+        if ext == 'ts' && application_js_exists
+          contains('<%= vite_typescript_tag "inertia" %>')
+          contains("<%= vite_typescript_tag 'application' %>")
+        elsif ext == 'ts' && !application_js_exists
           contains('<%= vite_typescript_tag "inertia" %>')
+          contains("<%= vite_javascript_tag 'application' %>")
         else
           contains('<%= vite_javascript_tag "inertia" %>')
+          contains("<%= vite_javascript_tag 'application' %>")
         end
         if framework == :react
           contains('<%= vite_react_refresh_tag %>')