fix(create): make --packageManager flag work (#3498)

Author: mgred

packages/create/index.js

@@ -75,7 +75,15 @@ function main(argv, error = console.error, log = console.log) {
 }
 
 // Which package manager will be used in the new project
-constpkgMgr=args['packageManager']||detectRunningUnderYarn() ? 'yarn' : 'npm';
+letpkgMgr=args['packageManager'];
+
+if(!pkgMgr){
+pkgMgr=detectRunningUnderYarn() ? 'yarn' : 'npm';
+}elseif(pkgMgr!=='yarn'&&pkgMgr!=='npm'){
+error('Please select between \'yarn\' and \'npm\' when providing --packageManager');
+usage(error);
+return1;
+}
 
 log_verbose('Running with',process.argv);
 log_verbose('Environment',process.env);

packages/create/test.js

@@ -70,6 +70,16 @@ wkspContent = read('default_to_yarn/WORKSPACE');
 if(wkspContent.indexOf('yarn_install(')<0){
 fail('should use yarn by default');
 }
+
+exitCode=main(['use_npm_with_yarn','--packageManager=npm']);
+if(exitCode!=0)fail('should be success');
+wkspContent=read('use_npm_with_yarn/WORKSPACE');
+if(wkspContent.indexOf('npm_install(')<0){
+fail('should use npm as selected');
+}
+
+exitCode=main(['neither_yarn_nor_npm','--packageManager=foo']);
+if(exitCode!=1)fail('should exit 1 when selecting neither \'yarn\' nor \'npm\'');
 // TODO: run bazel in the new directory to verify a build works
 
 exitCode=main(['--typescript','with_ts'],captureError);