create plugin adds newly created plugin as a dependency in app package. adds to the plugins list in the app

frontend/packages/cli/src/commands/createPlugin.ts

@@ -61,6 +61,58 @@ export const createFileFromTemplate = (
   }
 };
 
+const sortObjectByKeys = (obj: {[name in string]: string}) => {
+  return Object.keys(obj)
+          .sort((a: string, b: string): number => a > b ? 1 : 0)
+          .reduce((result:{[name in string]: string}, key: string) => {
+            result[key] = obj[key];
+            return result;
+          }, {});
+}
+
+const capitalize = (str: string): string => str.charAt(0).toUpperCase() + str.slice(1);
+
+const addExportStatement = (file: string, exportStatement: string) => {
+  const newContents = fs
+    .readFileSync(file, 'utf8')
+    .split('\n')
+    .filter(Boolean) // get rid of empty lines
+    .concat([exportStatement])
+    .sort()
+    .concat(['']) // newline at end of file
+    .join('\n');
+
+  fs.writeFileSync(file, newContents, 'utf8');
+};
+
+export const addPluginDependencyToApp = (rootDir: string, pluginName: string): string => {
+  const pluginPackage = `@spotify-backstage/plugin-${pluginName}`;
+  const pluginPackageVersion = "0.0.0";
+  const packageFile = path.join(rootDir, 'packages', 'app', 'package.json');
+  const packageFileContent = fs.readFileSync(packageFile, 'utf-8').toString();
+  const packageFileJson = JSON.parse(packageFileContent);
+  const dependencies = packageFileJson.dependencies;
+  
+  if (typeof dependencies[pluginPackage] !== 'undefined') {
+    throw new Error(`Plugin ${pluginPackage} already exists in ${packageFile}`);
+  }
+  
+  dependencies[pluginPackage] = pluginPackageVersion;
+  packageFileJson.dependencies = sortObjectByKeys(dependencies);
+  fs.writeFileSync(packageFile, JSON.stringify(packageFileJson, null, 2), 'utf-8');
+  fs.appendFileSync(packageFile, '\n', 'utf-8'); // new line at end of file
+  return pluginPackage;
+}
+
+export const addPluginToApp = (rootDir: string, pluginName: string) => {
+  const pluginPackage = `@spotify-backstage/plugin-${pluginName}`;
+  const pluginNameCapitalized = pluginName.split('-').map(name => capitalize(name)).join('');
+  const pluginExport = `\nexport { default as ${pluginNameCapitalized} } from '${pluginPackage}';`;
+  const pluginsFile = path.join(rootDir, 'packages', 'app', 'src', 'plugins.ts');
+
+  addExportStatement(pluginsFile, pluginExport);
+}
+
 export const createFromTemplateDir = async (
   templateFolder: string,
   destinationFolder: string,
@@ -179,6 +231,7 @@ const buildPlugin = async (pluginFolder: string) => {
 };
 
 const createPlugin = async (): Promise<any> => {
+  
   const questions: Question[] = [
     {
       type: 'input',
@@ -210,6 +263,9 @@ const createPlugin = async (): Promise<any> => {
     await createFromTemplateDir(templateFolder, destinationFolder, answers);
     await buildPlugin(destinationFolder);
 
+    addPluginDependencyToApp(rootDir, answers.id);
+    addPluginToApp(rootDir, answers.id);
+    
     console.log();
     console.log(
       chalk.green(