`exit` causes obscure error in ScriptMethod ETS methods

[mklement0]

Note: Calling exit from a function or method is unusual, but it works in functions and in class methods, but not from ScriptMethod methods on custom objects, where it fails with an obscure error.

Steps to reproduce

pwsh -noprofile -c '($obj = [pscustomobject]::new()) | Add-Member -MemberType ScriptMethod Foo { exit 5 }; $obj.Foo()'
$LASTEXITCODE | Should -Be 5

Expected behavior

There should be no output, and the test should succeed.

Actual behavior

An error is reported, and the test fails, because the exit statement wasn't effective (the exit code was implicitly set by the unexpected statement-terminating error, to 1):

MethodInvocationException: Exception calling "Foo" with "0" argument(s): "System error."
InvalidResult:
Line |
   1 | $LASTEXITCODE | Should -Be 5
     | Expected 5, but got 1.

Environment data

PowerShell Core 7.0.0

[bpayette]

Hi @mklement0 Here's what's happening. The exit keyword throws a special exception to indicate that the engine is exiting. As currently implemented, this exception is being caught by the implementation of PSScriptMethod in PSScriptMethod.Invoke() and wrapped in a MethodInvocationException. Looking at the inner exception, you'll see the original exception:

PS[1] (41) > $e.Exception.InnerException.GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     False    ExitException                            System.Management.Automation.FlowControlException

PS[1] (42) >

IIRC this rather interesting exception handling strategy was done so that you could use script methods in F&O without worrying about infinite recursion if a method used in formatting errors had an error.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has been marked as "No Activity" as there has been no activity for 6 months. It has been closed for housekeeping purposes.