René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Redirection of external command output breaks ANSI sequences","articleBody":"### Prerequisites\n\n- [X] Write a descriptive title.\n- [X] Make sure you are able to repro it on the [latest released version](https://github.com/PowerShell/PowerShell/releases)\n- [X] Search the existing issues.\n- [X] Refer to the [FAQ](https://github.com/PowerShell/PowerShell/blob/master/docs/FAQ.md).\n- [X] Refer to [Differences between Windows PowerShell 5.1 and PowerShell](https://docs.microsoft.com/powershell/scripting/whats-new/differences-from-windows-powershell).\n\n### Steps to reproduce\n\n* Have Git for Windows installed\r\n* Run Powershell 7.21 (either in ConHost or the new Terminal app, bug is reproducible in both)\r\n* Create the following simple function:\r\n```\r\nfunction Test-Ansi {\r\n    $VerbosePreference = 'Continue'\r\n    Write-Verbose '------ Before ------'\r\n    \u0026 \"$Env:ProgramFiles\\Git\\usr\\bin\\patch.exe\" --help \u003e $null\r\n    Write-Verbose '------ After ------'\r\n}\r\n```\r\n* Observe properly formatted coloring for the line before\r\n* Observe line after being uncolored and ANSI sequences instead printed verbatim\r\n\r\n# Additional Notes\r\n\r\nThis behaviour was only observed in PowerShell 7 - running the same function on PowerShell 5 yields the expected behaviour with no breaking changes to the ANSI output. \r\n\r\nIt also doesn't make a difference whether the redirection is done via `| Out-Null` or doing a `$null` assignment. Even just redirecting stderr via `2\u003e$null` triggers the issue. _Not_ redirecting the command is the only way to have it run without breaking.\r\n\r\nThe issue also occurs independent of invocation, `Invoke-Expression` results in this bug as does using `Start-Command`.\r\n\r\nAlso running this slightly tweaked function:\r\n```\r\nfunction Test-Ansi-Async {\r\n    $VerbosePreference = 'Continue'\r\n    Write-Verbose '------ Before ------'\r\n    Start-Process -FilePath \"C:\\Program Files\\Git\\usr\\bin\\patch.exe\" -RedirectStandardOutput NUL -ArgumentList '--help' -NoNewWindow\r\n    Write-Verbose '------ After ------'\r\n}\r\n```\r\nwill yield different bugs in ConHost or Windows Terminal:\r\n\r\n* In ConHost browsing through command history will have corrupted output, with characters remaining on screen between history items\r\n* In Windows Terminal the ANSI color codes of the next command will be corruped\r\n\r\n(See screenshots for each case).\r\n\r\nIn both cases pressing \"Enter\" without any input restores proper output at the prompt.\n\n### Expected behavior\n\n```console\nVERBOSE: ------ Before ------\r\nVERBOSE: ------ After ------\n```\n\n\n### Actual behavior\n\n```console\nVERBOSE: ------ Before ------\r\n←[33;1mVERBOSE: ------ After ------←[0m\n```\n\n\n### Error details\n\n```console\nPS C:\\Windows\\System32› Get-Error\r\nPS C:\\Windows\\System32›\n```\n\n\n### Environment data\n\n```powershell\nName                           Value\r\n----                           -----\r\nPSVersion                      7.2.1\r\nPSEdition                      Core\r\nGitCommitId                    7.2.1\r\nOS                             Microsoft Windows 10.0.22000\r\nPlatform                       Win32NT\r\nPSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}\r\nPSRemotingProtocolVersion      2.3\r\nSerializationVersion           1.1.0.1\r\nWSManStackVersion              3.0\n```\n\n\n### Visuals\n\n# Visual Corruption in ConHost\r\n\r\n![2022-01-20_ConHost-ANSI-Bug](https://user-images.githubusercontent.com/9436503/150246602-cb223f99-dd1d-48d4-b0b4-a640910e4801.png)\r\n\r\n# Broken ANSI Codes in Windows Terminal\r\n\r\n![2022-01-20_Terminal-ANSI-Bug](https://user-images.githubusercontent.com/9436503/150246904-8c27fbb4-e203-490b-a272-66bfbbc3b0a1.png)\r\n\r\n","author":{"url":"https://github.com/PatTheMav","@type":"Person","name":"PatTheMav"},"datePublished":"2022-01-20T01:40:52.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/16775/PowerShell/issues/16775"}