[rush] Do not print Rush alerts when --json or --quiet is specified

common/changes/@microsoft/rush/fix-5228-alerts-quiet-json_2026-10-07.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Do not print Rush alerts when console output is restricted by \"--quiet\" or \"--json\", so that commands such as \"rush list --json\" write only JSON to stdout.",
+      "type": "patch"
+    }
+  ]
+}

libraries/rush-lib/src/cli/RushCommandLineParser.ts

@@ -490,7 +490,9 @@ export class RushCommandLineParser extends CommandLineParser {
         try {
           const { configuration: experiments } = this.rushConfiguration.experimentsConfiguration;
 
-          if (experiments.rushAlerts) {
+          // Alerts are written to stdout, so they must not be printed when console output is restricted
+          // (for example "--json" or "--quiet"), or they would corrupt machine-readable output.
+          if (experiments.rushAlerts && !this.#restrictConsoleOutput) {
             // TODO: Fix this
             // eslint-disable-next-line @typescript-eslint/no-explicit-any
             const actionName: string = (this as any)

libraries/rush-lib/src/cli/test/RushCommandLineParserAlerts.test.ts

@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
+// See LICENSE in the project root for license information.
+
+import { RushCommandLineParser } from '../RushCommandLineParser';
+import { EnvironmentConfiguration } from '../../api/EnvironmentConfiguration';
+import { RushAlerts } from '../../utilities/RushAlerts';
+
+describe('RushCommandLineParser alerts', () => {
+  const originalArgv: string[] = process.argv;
+  let originalExitCode: string | number | undefined;
+  let printAlertsAsync: jest.Mock<Promise<void>, []>;
+
+  beforeEach(() => {
+    originalExitCode = process.exitCode;
+    process.exitCode = undefined;
+    printAlertsAsync = jest.fn(async () => undefined);
+    jest
+      .spyOn(RushAlerts, 'loadFromConfigurationAsync')
+      .mockResolvedValue({ printAlertsAsync } as unknown as RushAlerts);
+    jest.spyOn(console, 'log').mockImplementation(() => undefined);
+    jest.spyOn(console, 'error').mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    process.exitCode = originalExitCode;
+    process.argv = originalArgv;
+    EnvironmentConfiguration.reset();
+    jest.restoreAllMocks();
+  });
+
+  async function executeAsync(args: string[]): Promise<void> {
+    process.argv = ['pretend-this-is-node.exe', 'pretend-this-is-rush', ...args];
+    const parser: RushCommandLineParser = new RushCommandLineParser({
+      cwd: `${__dirname}/rushAlertsRepo`,
+      reporterCloseAsync: async () => undefined
+    });
+    await expect(parser.executeAsync(args)).resolves.toBe(true);
+  }
+
+  it('prints alerts after a command when console output is not restricted', async () => {
+    await executeAsync(['list']);
+
+    expect(printAlertsAsync).toHaveBeenCalledTimes(1);
+  });
+
+  it.each(['list --json', '--quiet list', '-q list'])(
+    'does not print alerts for "rush %s"',
+    async (commandLine) => {
+      await executeAsync(commandLine.split(' '));
+
+      expect(RushAlerts.loadFromConfigurationAsync).not.toHaveBeenCalled();
+      expect(printAlertsAsync).not.toHaveBeenCalled();
+    }
+  );
+});

libraries/rush-lib/src/cli/test/rushAlertsRepo/a/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "a",
+  "version": "1.0.0"
+}

libraries/rush-lib/src/cli/test/rushAlertsRepo/common/config/rush/experiments.json

@@ -0,0 +1 @@
+{ "rushAlerts": true }

libraries/rush-lib/src/cli/test/rushAlertsRepo/rush.json

@@ -0,0 +1,10 @@
+{
+  "pnpmVersion": "4.5.0",
+  "rushVersion": "5.0.0",
+  "projects": [
+    {
+      "packageName": "a",
+      "projectFolder": "a"
+    }
+  ]
+}