fix(@angular/cli): handle duplicate arguments

With this change we add a Yargs middleware that normalizes non Array options when the argument has been provided multiple times.

By default, when an option is non array and it is provided multiple times in the command line, yargs
will not override it's value but instead it will be changed to an array unless `duplicate-arguments-array` is disabled.
But this option also have an effect on real array options which isn't desired.

See: yargs/yargs-parser#163 (comment)

Closes #22956

packages/angular/cli/src/command-builder/command-runner.ts

@@ -33,6 +33,7 @@ import { PackageManagerUtils } from '../utilities/package-manager';
 import { CommandContext, CommandModuleError, CommandScope } from './command-module';
 import { addCommandModuleToYargs, demandCommandFailureMessage } from './utilities/command';
 import { jsonHelpUsage } from './utilities/json-help';
+import { normalizeOptionsMiddleware } from './utilities/normalize-options-middleware';
 
 const COMMANDS = [
   VersionCommandModule,
@@ -145,6 +146,7 @@ export async function runCommand(args: string[], logger: logging.Logger): Promis
     })
     .demandCommand(1, demandCommandFailureMessage)
     .recommendCommands()
+    .middleware(normalizeOptionsMiddleware)
     .version(false)
     .showHelpOnFail(false)
     .strict()

packages/angular/cli/src/command-builder/utilities/normalize-options-middleware.ts

@@ -0,0 +1,37 @@
+/**
+ * @license
+ * Copyright Google LLC 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
+ */
+
+import * as yargs from 'yargs';
+
+/**
+ * A Yargs middleware that normalizes non Array options when the argument has been provided multiple times.
+ *
+ * By default, when an option is non array and it is provided multiple times in the command line, yargs
+ * will not override it's value but instead it will be changed to an array unless `duplicate-arguments-array` is disabled.
+ * But this option also have an effect on real array options which isn't desired.
+ *
+ * See: https://github.com/yargs/yargs-parser/pull/163#issuecomment-516566614
+ */
+export function normalizeOptionsMiddleware(args: yargs.Arguments): void {
+  // `getOptions` is not included in the types even though it's public API.
+  // https://github.com/yargs/yargs/issues/2098
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const { array } = (yargs as any).getOptions();
+  const arrayOptions = new Set(array);
+
+  for (const [key, value] of Object.entries(args)) {
+    if (key !== '_' && Array.isArray(value) && !arrayOptions.has(key)) {
+      const newValue = value.pop();
+      // eslint-disable-next-line no-console
+      console.warn(
+        `Option '${key}' has been specified multiple times. The value '${newValue}' will be used.`,
+      );
+      args[key] = newValue;
+    }
+  }
+}

tests/legacy-cli/e2e/tests/misc/duplicate-command-line-option.ts

@@ -0,0 +1,19 @@
+import { ng } from '../../utils/process';
+import { expectFileToExist } from '../../utils/fs';
+
+export default async function () {
+  const { stderr } = await ng(
+    'generate',
+    'component',
+    'test-component',
+    '--style=scss',
+    '--style=sass',
+  );
+
+  const warningMatch = `Option 'style' has been specified multiple times. The value 'sass' will be used`;
+  if (!stderr.includes(warningMatch)) {
+    throw new Error(`Expected stderr to contain: "${warningMatch}".`);
+  }
+
+  await expectFileToExist('src/app/test-component/test-component.component.sass');
+}