fix(@angular/cli): temporarily limit npm to version 6

This change will display an error message if using npm 7 (or versions earlier than 6). This is a temporarily change while npm 7 usability concerns are addressed.

lib/packages.ts

@@ -88,7 +88,7 @@ function loadPackageJson(p: string) {
       case 'engines':
         pkg['engines'] = {
           'node': '>= 10.13.0',
-          'npm': '>= 6.11.0',
+          'npm': '^6.11.0',
           'yarn': '>= 1.13.0',
         };
         break;

packages/angular/cli/commands/add-impl.ts

@@ -15,7 +15,7 @@ import { Arguments } from '../models/interface';
 import { RunSchematicOptions, SchematicCommand } from '../models/schematic-command';
 import { colors } from '../utilities/color';
 import { installPackage, installTempPackage } from '../utilities/install-package';
-import { getPackageManager } from '../utilities/package-manager';
+import { ensureCompatibleNpm, getPackageManager } from '../utilities/package-manager';
 import {
   NgAddSaveDepedency,
   PackageManifest,
@@ -39,6 +39,8 @@ export class AddCommand extends SchematicCommand<AddCommandSchema> {
   }
 
   async run(options: AddCommandSchema & Arguments) {
+    ensureCompatibleNpm();
+
     if (!options.collection) {
       this.logger.fatal(
         `The "ng add" command requires a name argument to be specified eg. ` +

packages/angular/cli/commands/new-impl.ts

@@ -7,6 +7,7 @@
  */
 import { Arguments } from '../models/interface';
 import { SchematicCommand } from '../models/schematic-command';
+import { ensureCompatibleNpm } from '../utilities/package-manager';
 import { Schema as NewCommandSchema } from './new';
 
 
@@ -21,6 +22,8 @@ export class NewCommand extends SchematicCommand<NewCommandSchema> {
   }
 
   public async run(options: NewCommandSchema & Arguments) {
+    ensureCompatibleNpm();
+
     // Register the version of the CLI in the registry.
     const packageJson = require('../package.json');
     const version = packageJson.version;

packages/angular/cli/commands/update-impl.ts

@@ -18,7 +18,7 @@ import { SchematicEngineHost } from '../models/schematic-engine-host';
 import { colors } from '../utilities/color';
 import { runTempPackageBin } from '../utilities/install-package';
 import { writeErrorToLogFile } from '../utilities/log-file';
-import { getPackageManager } from '../utilities/package-manager';
+import { ensureCompatibleNpm, getPackageManager } from '../utilities/package-manager';
 import {
   PackageIdentifier,
   PackageManifest,
@@ -267,6 +267,8 @@ export class UpdateCommand extends Command<UpdateCommandSchema> {
 
   // tslint:disable-next-line:no-big-function
   async run(options: UpdateCommandSchema & Arguments) {
+    ensureCompatibleNpm();
+
     // Check if the current installed CLI version is older than the latest version.
     if (!disableVersionCheck && await this.checkCLILatestVersion(options.verbose, options.next)) {
       this.logger.warn(

packages/angular/cli/utilities/package-manager.ts

@@ -54,3 +54,26 @@ export async function getPackageManager(root: string): Promise<PackageManager> {
   //       Potentially with a prompt to choose and optionally set as the default.
   return packageManager || PackageManager.Npm;
 }
+
+/**
+ * Checks if the npm version is version 6.x.  If not, display a message and exit.
+ */
+export function ensureCompatibleNpm() {
+  try {
+    const version = execSync('npm --version', {encoding: 'utf8', stdio: 'pipe'}).trim();
+    const major = Number(version.match(/^(\d+)\./)?.[1]);
+    if (major === 6) {
+      return;
+    }
+
+    // tslint:disable-next-line: no-console
+    console.error(
+      `npm version ${version} detected.\n` +
+      'The Angular CLI currently requires npm version 6.\n\n' +
+      'Please install a compatible version to proceed (`npm install --global npm@6`).\n',
+    );
+    process.exit(3);
+  } catch {
+    // npm is not installed
+  }
+}

tests/legacy-cli/e2e/tests/misc/npm-7.ts

@@ -0,0 +1,45 @@
+import { getActivePackageManager } from '../../utils/packages';
+import { ng, npm } from '../../utils/process';
+import { expectToFail } from '../../utils/utils';
+
+const errorText = 'The Angular CLI currently requires npm version 6.';
+
+export default async function() {
+  // Only relevant with npm as a package manager
+  if (getActivePackageManager() !== 'npm') {
+    return;
+  }
+
+  const currentDirectory = process.cwd();
+  try {
+    // Install version 7.x
+    await npm('install', '--global', 'npm@7');
+
+    // Ensure `ng add` exits and shows npm error
+    const { message: stderrAdd } = await expectToFail(() => ng('add'));
+    if (!stderrAdd.includes(errorText)) {
+      throw new Error('ng add expected to show npm version error.');
+    }
+
+    // Ensure `ng update` exits and shows npm error
+    const { message: stderrUpdate } = await expectToFail(() => ng('update'));
+    if (!stderrUpdate.includes(errorText)) {
+      throw new Error('ng update expected to show npm version error.');
+    }
+
+    // Ensure `ng new` exits and shows npm error
+    // Must be outside the project for `ng new`
+    process.chdir('..');
+    const { message: stderrNew } = await expectToFail(() => ng('new'));
+    if (!stderrNew.includes(errorText)) {
+      throw new Error('ng new expected to show npm version error.');
+    }
+  } finally {
+    // Change directory back
+    process.chdir(currentDirectory);
+
+    // Reset version back to 6.x
+    await npm('install', '--global', 'npm@6');
+  }
+
+}