feat(toolkit): print available templates when --language is omitted (#1159)

When --language is omitted from a call to "cdk init", instead of
just printing the supported languages, we now print all options,
including template types.

Author: Elad Ben-Israel

packages/aws-cdk/bin/cdk.ts

@@ -206,7 +206,7 @@ async function initCommandLine() {
         if (args.list) {
           return await printAvailableTemplates(language);
         } else {
-          return await cliInit(args.TEMPLATE || 'default', language);
+          return await cliInit(args.TEMPLATE, language);
         }
 
       default:

packages/aws-cdk/lib/init.ts

@@ -18,8 +18,15 @@ const CDK_HOME = process.env.CDK_HOME ? path.resolve(process.env.CDK_HOME) : pat
 /**
  * Initialize a CDK package in the current directory
  */
-export async function cliInit(type: string, language: string | undefined, canUseNetwork?: boolean) {
-  const template = (await availableInitTemplates).find(t => t.hasName(type));
+export async function cliInit(type?: string, language?: string, canUseNetwork?: boolean) {
+  if (!type && !language) {
+    await printAvailableTemplates();
+    return;
+  }
+
+  type = type || 'default'; // "default" is the default type (and maps to "app")
+
+  const template = (await availableInitTemplates).find(t => t.hasName(type!));
   if (!template) {
     await printAvailableTemplates(language);
     throw new Error(`Unknown init template: ${type}`);