Debugger won't run until `ENTER` is pressed in integrated console

Prerequisites

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• I have searched all issues to ensure it has not already been reported.
• I have read the troubleshooting guide.
• I have verified that I am using the latest version of Visual Studio Code and the PowerShell extension.

Summary

This is currently only happening with v2021.8.1-preview (the PowerShell Preview extension) and PowerShell 7, but it happens on Windows and macOS. @SeeminglyScience confirmed for me: run any PowerShell script in the debugger, it won’t actually do anything (like run to a breakpoint or completion) until you manually go to the integrated console and press ENTER.

PowerShell Version

Name                           Value
----                           -----
PSVersion                      7.1.4
PSEdition                      Core
GitCommitId                    7.1.4
OS                             Microsoft Windows 10.0.22000
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visual Studio Code Version

1.59.1
3866c3553be8b268c8a7f8c0482c0c0177aa8bfa
x64

Extension Version

ms-vscode.powershell-preview@2021.8.1

Steps to Reproduce

1. Run PowerShell script in debugger
2. It hangs until ENTER is sent

Visuals

No response

Logs

No response

[andschwa]

Haha, oops, our bad. @rjmholt and I added the Stop() registration at the last minute. That explains why this was only in 2.4.8 and not 2.4.7.

[SeeminglyScience]

@andschwa I think it’s this:

https://github.com/PowerShell/PowerShellEditorServices/blob/6a19daf5bc3e8547fbdc10f351ac2a81d76f9cec/src/PowerShellEditorServices/Services/PowerShellContext/PowerShellContextService.cs#L768

        public async Task<IEnumerable<TResult>> ExecuteCommandAsync<TResult>(
            PSCommand psCommand,
            StringBuilder errorMessages,
            ExecutionOptions executionOptions,
            CancellationToken cancellationToken = default)
        {
            // (...)
            cancellationToken.Register(() => shell.Stop());

Linked cancellation token sources work by essentially registering a cancellation handler on the target token. I’m guessing the handlers are invoked sequentially on the same thread, and if that’s the case then the link handler will never fire because shell.Stop won’t finish. The pipeline won’t stop until ReadLine returns, and ReadLine won’t return until the next cancel handler fires.

Might get away with just changing it to shell.BeginStop()