"Welcome to Flutter" and "Waiting for lock" messages break --machine commands

[pchampio]

sudo flutter channel --version --machine is responding with a non json output, this break other toolkit/ci-cd that are relying on this --machine flag go-flutter-desktop/go-flutter#384.

$ sudo flutter channel --version --machine     
Woah! You appear to be trying to run flutter as root.
   We strongly recommend running the flutter tool without superuser privileges.
  /
📎
{
  "frameworkVersion": "1.16.4-pre.88",
  "channel": "master",
  "repositoryUrl": "https://github.com/flutter/flutter.git",
  "frameworkRevision": "ab14307e0c77e4a03ea23ccaa68436d9128a445d",
  "frameworkCommitDate": "2020-04-03 00:56:01 -0400",
  "engineRevision": "f5127cc07a762de774b7e941fe6eb402c97aa1b3",
  "dartSdkVersion": "2.8.0 (build 2.8.0-dev.19.0 fae35fca47)"
}

  ╔════════════════════════════════════════════════════════════════════════════╗
  ║                 Welcome to Flutter! - https://flutter.dev                  ║
  ║                                                                            ║
  ║ The Flutter tool uses Google Analytics to anonymously report feature usage ║
  ║ statistics and basic crash reports. This data is used to help improve      ║
  ║ Flutter tools over time.                                                   ║
  ║                                                                            ║
  ║ Flutter tool analytics are not sent on the very first run. To disable      ║
  ║ reporting, type 'flutter config --no-analytics'. To display the current    ║
  ║ setting, type 'flutter config'. If you opt out of analytics, an opt-out    ║
  ║ event will be sent, and then no further information will be sent by the    ║
  ║ Flutter tool.                                                              ║
  ║                                                                            ║
  ║ By downloading the Flutter SDK, you agree to the Google Terms of Service.  ║
  ║ Note: The Google Privacy Policy describes how data is handled in this      ║
  ║ service.                                                                   ║
  ║                                                                            ║
  ║ Moreover, Flutter includes the Dart SDK, which may send usage metrics and  ║
  ║ crash reports to Google.                                                   ║
  ║                                                                            ║
  ║ Read about data we send with crash reports:                                ║
  ║ https://flutter.dev/docs/reference/crash-reporting                         ║
  ║                                                                            ║
  ║ See Google's privacy policy:                                               ║
  ║ https://policies.google.com/privacy                                        ║
  ╚════════════════════════════════════════════════════════════════════════════╝

[pchampio]

$ flutter --version --machine
Waiting for another flutter command to release the startup lock...
{
  "frameworkVersion": "1.17.0",
  "channel": "beta",
  "repositoryUrl": "https://github.com/flutter/flutter.git",
  "frameworkRevision": "d3ed9ec945f8869f0e136c357d0c2a6be2b60c98",
  "frameworkCommitDate": "2020-04-06 14:07:34 -0700",
  "engineRevision": "c9506cb8e93e5e8879152ff5c948b175abb5b997",
  "dartSdkVersion": "2.8.0 (build 2.8.0-dev.18.0 eea9717938)"
}

[GeertJohan]

The non-JSON output can be written to stderr, so that stdout is still 'clean' for machines to read.

[jonahwilliams]

We've moved some of the diagnostic messages to stderr, though this does not yet include the welcome message. This could be fixed by detecting if a machine flag was passed and eliding it.

[sigurdm]

This could be fixed by detecting if a machine flag was passed and eliding it.

Is there any reason to not always output the welcome message on stderr?

[christopherfujino]

This could be fixed by detecting if a machine flag was passed and eliding it.

Is there any reason to not always output the welcome message on stderr?

I believe there have been concerns (from product) that the default command prompt setup on Windows colors STDERR red, and that too much red would scare new users.