fix(nx): make package manager detection a bit smarter

In @nrwl/tao this covers the cases where no lock files exist and in create-nx-workspace we add
support for detecting pnpm installation

packages/create-nx-workspace/bin/create-nx-workspace.ts

@@ -100,27 +100,48 @@ function showHelp() {
 }
 
 function determinePackageManager() {
+  let packageManager = getPackageManagerFromAngularCLI();
+  if (packageManager === 'npm' || isPackageManagerInstalled(packageManager)) {
+    return packageManager;
+  }
+
+  if (isPackageManagerInstalled('yarn')) {
+    return 'yarn';
+  }
+
+  if (isPackageManagerInstalled('pnpm')) {
+    return 'pnpm';
+  }
+
+  return 'npm';
+}
+
+function getPackageManagerFromAngularCLI(): string {
   // If you have Angular CLI installed, read Angular CLI config.
-  // If it isn't not installed, default to 'yarn'.
-  let packageManager: string;
+  // If it isn't installed, default to 'yarn'.
   try {
-    packageManager = execSync('ng config -g cli.packageManager', {
+    return execSync('ng config -g cli.packageManager', {
       stdio: ['ignore', 'pipe', 'ignore'],
       timeout: 500
     })
       .toString()
       .trim();
   } catch (e) {
-    packageManager = 'yarn';
+    return 'yarn';
   }
+}
+
+function isPackageManagerInstalled(packageManager: string) {
+  let isInstalled = false;
   try {
     execSync(`${packageManager} --version`, {
       stdio: ['ignore', 'ignore', 'ignore']
     });
+    isInstalled = true;
   } catch (e) {
-    packageManager = 'npm';
+    /* do nothing */
   }
-  return packageManager;
+  return isInstalled;
 }
 
 function determineWorkspaceName(parsedArgs: any) {

packages/tao/src/commands/generate.ts

@@ -32,6 +32,7 @@ import { logger } from '../shared/logger';
 import { commandName, printHelp } from '../shared/print-help';
 import * as fs from 'fs';
 import minimist = require('minimist');
+import { execSync } from 'child_process';
 
 interface GenerateOptions {
   collectionName: string;
@@ -161,20 +162,48 @@ async function detectPackageManager(
     }
   }
 
-  const yarnLockFileExists = await host.exists('yarn.lock' as any).toPromise();
-  if (yarnLockFileExists) {
+  if (await fileExists(host, 'yarn.lock')) {
     return 'yarn';
   }
-  const pnpmLockFileExists = await host
-    .exists('pnpm-lock.yaml' as any)
-    .toPromise();
-  if (pnpmLockFileExists) {
+
+  if (await fileExists(host, 'pnpm-lock.yaml')) {
+    return 'pnpm';
+  }
+
+  if (await fileExists(host, 'package-lock.json')) {
+    return 'npm';
+  }
+
+  // If we get here, there are no lock files, so lets check for package managers in our preferred order
+  if (isPackageManagerInstalled('yarn')) {
+    return 'yarn';
+  }
+
+  if (isPackageManagerInstalled('pnpm')) {
     return 'pnpm';
   }
 
   return 'npm';
 }
 
+function fileExists(
+  host: virtualFs.Host<any>,
+  fileName: string
+): Promise<boolean> {
+  return host.exists(fileName as any).toPromise();
+}
+
+function isPackageManagerInstalled(packageManager: string) {
+  try {
+    execSync(`${packageManager} --version`, {
+      stdio: ['ignore', 'ignore', 'ignore']
+    });
+    return true;
+  } catch (e) {
+    return false;
+  }
+}
+
 async function createWorkflow(
   fsHost: virtualFs.Host<fs.Stats>,
   root: string,