feat: Add experimental CLI for LoopBack 4

Usage:
npm i -g @loopback/cli
lb4 app <name>
lb4 extension <name>

Author: Raymond Feng

.prettierignore

@@ -1,5 +1,6 @@
 packages/*/dist
 packages/*/dist6
 packages/*/api-docs
+packages/cli/generators/*/templates
 package.json
 packages/*/package.json

packages/cli/.gitignore

@@ -0,0 +1,2 @@
+node_modules
+coverage

packages/cli/.npmrc

@@ -0,0 +1 @@
+package-lock=false

packages/cli/.prettierrc

@@ -0,0 +1,6 @@
+{
+  "bracketSpacing": false,
+  "singleQuote": true,
+  "printWidth": 80,
+  "trailingComma": "es5"
+}

packages/cli/.yo-rc.json

@@ -0,0 +1,2 @@
+{
+}

packages/cli/README.md

@@ -0,0 +1,57 @@
+# @loopback/cli
+
+This module contains the experimental CLI for LoopBack 4.
+
+## Installation
+
+Run the following command to install the CLI.
+
+`npm install -g @loopback/cli`
+
+## Usage
+
+1. To scaffold a LoopBack 4 application
+
+    `lb4 app`
+
+```
+Usage:
+  lb4 app [options] [<name>]
+
+Options:
+  -h,   --help             # Print the generator's options and usage
+        --skip-cache       # Do not remember prompt answers              Default: false
+        --skip-install     # Do not automatically install dependencies   Default: false
+        --applicationName  # Application name
+        --description      # Description for the application
+        --outdir           # Project root directory for the application
+        --tslint           # Enable tslint
+        --prettier         # Enable prettier
+        --mocha            # Enable mocha
+        --loopbackBuild    # Use @loopback/build
+
+Arguments:
+  name  # Project name for the application  Type: String  Required: false
+```
+
+2. To scaffold a LoopBack 4 extension
+
+    `lb4 extension`
+
+```
+Usage:
+  lb4 extension [options] [<name>]
+
+Options:
+  -h,   --help           # Print the generator's options and usage
+        --skip-cache     # Do not remember prompt answers             Default: false
+        --skip-install   # Do not automatically install dependencies  Default: false
+        --description    # Description for the extension
+        --outdir         # Project root directory for the extension
+        --tslint         # Enable tslint
+        --prettier       # Enable prettier
+        --mocha          # Enable mocha
+        --loopbackBuild  # Use @loopback/build
+        --componentName  # Component name
+
+```

packages/cli/bin/cli.js

@@ -0,0 +1,65 @@
+#!/usr/bin/env node
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: @loopback/cli
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+const assert = require('assert');
+const camelCaseKeys = require('camelcase-keys');
+const debug = require('debug')('loopback:cli');
+const minimist = require('minimist');
+const path = require('path');
+const yeoman = require('yeoman-environment');
+
+const opts = minimist(process.argv.slice(2), {
+  alias: {
+    help: 'h',
+    version: 'v',
+    commands: 'l',
+  },
+});
+
+if (opts.version) {
+  const ver = require('../package.json').version;
+  console.log('Version: %s', ver);
+  return;
+}
+
+var env = yeoman.createEnv();
+
+env.register(path.join(__dirname, '../generators/app'), 'loopback4:app');
+env.register(path.join(__dirname, '../generators/extension'), 'loopback4:extension');
+
+// list generators
+if (opts.commands) {
+  console.log('Available commands: ');
+  var list = Object.keys(env.getGeneratorsMeta())
+    .filter(name => /^loopback4:/.test(name))
+    .map(name => name.replace(/^loopback4:/, '  lb4 '));
+  console.log(list.join('\n'));
+  return;
+}
+
+const args = opts._;
+const originalCommand = args.shift();
+let command = 'loopback4:' + (originalCommand || 'app');
+const supportedCommands = env.getGeneratorsMeta();
+
+if (!(command in supportedCommands)) {
+  command = 'loopback4:app';
+  args.unshift(originalCommand);
+  args.unshift(command);
+} else {
+  args.unshift(command);
+}
+
+debug('invoking generator', args);
+
+// `yo` is adding flags converted to CamelCase
+const options = camelCaseKeys(opts, {exclude: ['--', /^\w$/, 'argv']});
+Object.assign(options, opts);
+
+debug('env.run %j %j', args, options);
+env.run(args, options);

packages/cli/generators/app/index.js

@@ -0,0 +1,78 @@
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: @loopback/cli
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+const ProjectGenerator = require('../../lib/project-generator');
+const utils = require('../../lib/utils');
+
+module.exports = class extends ProjectGenerator {
+  // Note: arguments and options should be defined in the constructor.
+  constructor(args, opts) {
+    super(args, opts);
+  }
+
+  _setupGenerator() {
+    this.projectType = 'application';
+    this.option('applicationName', {
+      type: String,
+      description: 'Application name',
+    });
+    return super._setupGenerator();
+  }
+
+  setOptions() {
+    return super.setOptions();
+  }
+
+  promptProjectName() {
+    return super.promptProjectName();
+  }
+
+  promptProjectDir() {
+    return super.promptProjectDir();
+  }
+
+  promptApplication() {
+    const prompts = [
+      {
+        type: 'input',
+        name: 'applicationName',
+        message: 'Application class name:',
+        default: utils.toClassName(this.projectInfo.name) + 'Application',
+      },
+    ];
+
+    return this.prompt(prompts).then(props => {
+      Object.assign(this.projectInfo, props);
+    });
+  }
+
+  promptOptions() {
+    return super.promptOptions();
+  }
+
+  scaffold() {
+    return super.scaffold();
+  }
+
+  install() {
+    return super.install();
+  }
+
+  end() {
+    this.log();
+    this.log(
+      'Application %s is now created in %s.',
+      this.projectInfo.name,
+      this.projectInfo.outdir
+    );
+    this.log();
+    this.log('Next steps:');
+    this.log();
+    this.log('$ cd ' + this.projectInfo.outdir);
+    this.log('$ npm start');
+    this.log();
+  }
+};

packages/cli/generators/app/templates/index.js

@@ -0,0 +1,14 @@
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: <%= project.name %>
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+const nodeMajorVersion = +process.versions.node.split('.')[0];
+const dist = nodeMajorVersion >= 7 ? './dist' : './dist6';
+
+const application = (module.exports = require(dist));
+
+if (require.main === module) {
+  // Run the application
+  application.main();
+}

packages/cli/generators/app/templates/src/application.ts

@@ -0,0 +1,27 @@
+// Copyright IBM Corp. 2017. All Rights Reserved.
+// Node module: <%= project.name %>
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+import {Application, ApplicationConfig} from '@loopback/core';
+import {RestComponent} from '@loopback/rest';
+import {PingController} from './controllers/ping-controller';
+
+export class <%= project.applicationName %> extends Application {
+  constructor(options?: ApplicationConfig) {
+    // Allow options to replace the defined components array, if desired.
+    options = Object.assign(
+      {},
+      {
+        components: [RestComponent],
+      },
+      options,
+    );
+    super(options);
+    this.setupControllers();
+  }
+
+  setupControllers() {
+    this.controller(PingController);
+  }
+}