fix(@angular/cli): standardize TTY checks

packages/angular/cli/models/analytics.ts

@@ -14,6 +14,7 @@ import * as os from 'os';
 import * as ua from 'universal-analytics';
 import { v4 as uuidV4 } from 'uuid';
 import { getWorkspace, getWorkspaceRaw } from '../utilities/config';
+import { isTTY } from '../utilities/tty';
 
 const analyticsDebug = debug('ng:analytics');  // Generate analytics, including settings and users.
 const analyticsLogDebug = debug('ng:analytics:log');  // Actual logs of events.
@@ -359,7 +360,7 @@ export function setAnalyticsConfig(level: 'global' | 'local', value: string | bo
  */
 export async function promptGlobalAnalytics(force = false) {
   analyticsDebug('prompting global analytics.');
-  if (force || (process.stdout.isTTY && process.stdin.isTTY)) {
+  if (force || isTTY()) {
     const answers = await inquirer.prompt<{ analytics: boolean }>([
       {
         type: 'confirm',
@@ -407,7 +408,7 @@ export async function promptProjectAnalytics(force = false): Promise<boolean> {
     throw new Error(`Could not find a local workspace. Are you in a project?`);
   }
 
-  if (force || (process.stdout.isTTY && process.stdin.isTTY)) {
+  if (force || isTTY()) {
     const answers = await inquirer.prompt<{ analytics: boolean }>([
       {
         type: 'confirm',

packages/angular/cli/models/schematic-command.ts

@@ -37,6 +37,7 @@ import {
 } from '../utilities/config';
 import { parseJsonSchemaToOptions } from '../utilities/json-schema';
 import { getPackageManager } from '../utilities/package-manager';
+import { isTTY } from '../utilities/tty';
 import { isPackageNameSafeForAnalytics } from './analytics';
 import { BaseCommandOptions, Command } from './command';
 import { Arguments, CommandContext, CommandDescription, Option } from './interface';
@@ -299,7 +300,7 @@ export abstract class SchematicCommand<
       return undefined;
     });
 
-    if (options.interactive !== false && process.stdout.isTTY) {
+    if (options.interactive !== false && isTTY()) {
       workflow.registry.usePromptProvider((definitions: Array<schema.PromptDefinition>) => {
         const questions: inquirer.Questions = definitions.map(definition => {
           const question: inquirer.Question = {

packages/angular/cli/utilities/tty.ts

@@ -0,0 +1,15 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+export function isTTY(): boolean {
+  const force = process.env['NG_FORCE_TTY'];
+  if (force !== undefined) {
+    return !(force === '0' || force.toUpperCase() === 'FALSE');
+  }
+
+  return !!process.stdout.isTTY && !!process.stdin.isTTY;
+}