feat: merge with existing package.json rather than replacing it com…

…pletely

lib/install/template.rb

@@ -46,12 +46,30 @@ def package_json
   if @package_json.nil?
     require "package_json"
 
-    @package_json = PackageJson.read
+    @package_json = PackageJson.new
   end
 
   @package_json
 end
 
+# setup the package manager with default values
+# package_json.merge! do |pj|
+#   babel = pj.fetch("babel", {})
+#
+#   babel["presets"] ||= []
+#   babel["presets"].shift("./node_modules/shakapacker/package/babel/preset.js")
+#
+#   {
+#     "name" => "app",
+#     "private" => true,
+#     "version" => "0.1.0",
+#     "babel" => babel,
+#     "browserslist" => [
+#       "defaults"
+#     ]
+#   }.merge(pj)
+# end
+
 # Ensure there is `system!("bin/yarn")` command in `./bin/setup` file
 if (setup_path = Rails.root.join("bin/setup")).exist?
   native_install_command = package_json.manager.native_install_command.join(" ")

spec/generator_specs/generator_spec.rb

@@ -58,7 +58,7 @@
           expect(actual_content).to eq expected_content
         end
 
-        it "replaces package.json with the template file" do
+        it "replaces the package.json completely" do
           package_json = PackageJson.read(path_in_the_app)
 
           expect(package_json.fetch("name", "")).to eq("app")