Allow require of nativescript-cli as library (#2468)

The entry point of current cli is used only from `bin/tns`. In fact the `main` entry in package.json is used when you want to require the module, but CLI is never required. It's installed globally and spawned from it's bin dir (`bin` key in package.json defines which is the "entry" point when package is installed globally).
So I've changed the entry point to a file, that does not use commandDispatcher - when requiring {N} CLI as library, we'll not execute commands.
In order to allow executing specific device operations (like device detection through events), require the mobile-cli-lib's appbuilder bootstrap in the entry point. This will be fixed with other PR's and finally we'll not have to require this bootstrap.

Author: rosen-vladimirov

lib/common

@@ -0,0 +1,8 @@
+require("./bootstrap");
+
+$injector.overrideAlreadyRequiredModule = true;
+
+// Temporary!!! Should not require appbuilder's entry point of mobile-cli-lib,
+// but once we separate logics in mobile-cli-lib, we should be able to require only specific bootstrap.
+// Use this hack for now, as this will allow requiring {N} CLI as library directly and executing some device specific operations.
+require("./common/appbuilder/proton-bootstrap");

lib/nativescript-cli-lib-bootstrap.ts

@@ -0,0 +1,3 @@
+require("./nativescript-cli-lib-bootstrap");
+
+module.exports = $injector.publicApi;

lib/nativescript-cli-lib.ts

@@ -8,7 +8,7 @@
     "tns": "./bin/tns",
     "nativescript": "./bin/tns"
   },
-  "main": "./lib/nativescript-cli.js",
+  "main": "./lib/nativescript-cli-lib.js",
   "scripts": {
     "test": "node test-scripts/istanbul.js",
     "postinstall": "node postinstall.js",

package.json

@@ -0,0 +1,24 @@
+import { assert } from "chai";
+import * as fs from "fs";
+import * as path from "path";
+import * as childProcess from "child_process";
+const nodeArgs = require(path.join(__dirname, "..", "lib", "common", "scripts", "node-args")).getNodeArgs();
+
+describe("nativescript-cli-lib", () => {
+	it("is main entry of the package", () => {
+		const packageJsonContent = fs.readFileSync(path.join(__dirname, "..", "package.json")).toString();
+		const jsonContent = JSON.parse(packageJsonContent);
+		const expectedEntryPoint = "./lib/nativescript-cli-lib.js";
+		assert.deepEqual(jsonContent.main, expectedEntryPoint);
+	});
+
+	it("resolves publicly available module - deviceEmitter, when it is required", () => {
+		const pathToEntryPoint = path.join(__dirname, "..", "lib", "nativescript-cli-lib.js").replace(/\\/g, "\\\\");
+		// HACK: If we try to require the entry point directly, the below code will fail as mocha requires all test files before starting the tests.
+		// When the files are required, $injector.register adds each dependency to $injector's cache.
+		// For example $injector.register("errors", Errors) will add the errors module with its resolver (Errors) to $injector's cache.
+		// Calling $injector.require("errors", <path to errors file>), that's executed in our bootstrap, will fail, as the module errors is already in the cache.
+		// In order to workaround this problem, start new process and assert there. This way all files will not be required in it and $injector.require(...) will work correctly.
+		childProcess.execSync(`"${process.execPath}" ${nodeArgs.join(" ")} -e "var assert = require('chai').assert; var result = require('${pathToEntryPoint}'); assert.ok(result.deviceEmitter);"`);
+	});
+});