Get-Error can hang on certain exceptions

[jborean93]

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Steps to reproduce

There is something about the exception raised by Assembly.GetTypes() that is causing Get-Error to get stuck in some loop and use up all system resources. In dotnet 8 loading the System.Data.SqlClient causes an error when attempting to get the types of that assembly. While this is a known problem attempting to use Get-Error to produce more information causes the shell to hang and start to consume all the system resources.

I've narrowed it down to the formatting of this particular error record in the formatting code

PowerShell/src/System.Management.Automation/FormatAndOutput/DefaultFormatters/PowerShellCore_format_ps1xml.cs

Line 831 in b2ba584

Set-StrictMode -Off

. You can run this in pwsh with https://gist.github.com/jborean93/54a9c7fc999b13ddddaf36d716fe7916 to be able to step through the code that hangs. I haven't figured out what property on this particular exception is actually causing the problem but there is something there. My money is on Types or LoaderExceptions in $Error[0].Exception.InnerException.

Expected behavior

Add-Type -Assembly System.Data.SqlClient

# This will raise an exception
[System.Data.SqlClient.SqlCredential].Assembly.GetTypes()

# Calling Get-Error after "hangs"
Get-Error

Actual behavior

Shows the error without hanging

Error details

Nothing, it hangs

Environment data

Name                           Value
----                           -----
PSVersion                      7.4.1
PSEdition                      Core
GitCommitId                    7.4.1
OS                             Arch Linux
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visuals

No response

[ninmonkey]

I was having trouble getting tracing to log when running. I was able to figure out it seems to be in an infinite loop
It keeps running down until line 160, then jumps to 41, runs to 160, jumps to 41, and never quits looping.

I am piping a single ErrorRecord

40-160 maps to this script extent

Ideas

• error record's types are modified while looping
• Show-ErrorRecord is recursive and it's using LangyPrimatives to prevent conversion errors
• If you hit ctrl+c after Get-Error -- there are no errors added to $global:error.count

Maybe there isn't an error being thrown in Get-Error
Maybe it's a logic error, where the exit condition never occurs.
That would align with error's not being added on ctrl+c

I tried manually triggering conversion errors on the properties of the ErrorRecord, thinking one of the properties would throw. I get nulls, but nothing throws. That's partly what made me think there might not be errors thrown.

$NullStr = "`u{2400}"
$error[0].psobject.properties | %{
    $IsTrueNull = $null -eq $_.Value
    $Value?     = $IsTrueNull ? $NullStr : $_.Value
    $tinfo      = $IsTrueNull ? $NullStr : $_.Value.GetType()
    $tinfo_IsIEnumerable = $IsTrueNull ? $NullStr :
            ($null -ne $tinfo.GetInterface('IEnumerable'))            

    $render = $IsTrueNull ? $NullStr :
            $_.Value.ToString()

    [string]$LangyValue = ''
    $LangyOk = [System.Management.Automation.LanguagePrimitives]::TryConvertTo(
        $_.Value, [string], [ref]$LangyValue) -and $LangyValue -ne $null

    $Info = [ordered]@{
        Name               = $_.Name
        TrueNull           = $null -eq $_.Value
        Value              = $Value?
        Type               = $Tinfo
        TinfoIsIEnumerable = $tinfo_isIEnumerable
        ToStr              = $Render
        LangyOk            = $LangyOk
        Langy              = $LangyValue
    }
    [pscustomobject]$info
}|ft

Name                  TrueNull Type                                                              TinfoIsIEnumerable ToStr
----                  -------- ----                                                              ------------------ -----                                                                                                     
PSMessageDetails          True ␀                                                                 ␀                  ␀
Exception                False System.Management.Automation.MethodInvocationException            False              System.Management.Automation.MethodInvocationException: Exception calling "GetTypes" with "0" argument(s)…
TargetObject              True ␀                                                                 ␀                  ␀
CategoryInfo             False System.Management.Automation.ErrorCategoryInfo                    False              NotSpecified: (:) [], MethodInvocationException
FullyQualifiedErrorId    False System.String                                                     True               ReflectionTypeLoadException
ErrorDetails              True ␀                                                                 ␀                  ␀
InvocationInfo           False System.Management.Automation.InvocationInfo                       False              System.Management.Automation.InvocationInfo
ScriptStackTrace         False System.String                                                     True               at <ScriptBlock>, H:\data\2024\pwsh\sketch\2024-01-16-PwshCmdlet\debug_harness-iter2.ps1: line 37…
PipelineIterationInfo    False System.Collections.ObjectModel.ReadOnlyCollection`1[System.Int32] True               System.Collections.ObjectModel.ReadOnlyCollection`1[System.Int32]

[jborean93]

The problem occurs when trying to serialize an array of Type instances. In this case Assembly.GetTypes() contains an InnerException of ReflectionTypeLoadException with the Types property that is Type[]. The Type type has a lot of properties that is heavily nested and just contains a lot of runtime data that brings the serialization down to its knees. You can see this by doing ConvertTo-Json ([string]), the default depth shows how many properties need to be serialized and increasing the depth just causes it to hang.

A quick reproducer is

class MyException : Exception {
    [Type[]]$Types

    MyException ([string]$Message) : base($Message) {
        $this.Types = @([string], [int])
    }
}

$exc = [MyException]::new("custom")

try { throw $exc } catch {}
Get-Error

The formatter should handle this and probably just return FullName or Name instead of trying to serialize the whole Type instance. Funnily enough a [Type] property is just fine, the problem seems to occur when it's a collection of Type, in this case Type[].

[jborean93]

PR which can handle this issue (as well as other primitive types) #21085

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