Improve output format of caught exception, using Write-Error

Question

say I have the following script test-exception.ps1

[CmdletBinding()]
    param()

process {
    1/0
}

if I run it, I get

Tentative de division par zéro.
Au caractère U:\test-exception.ps1:5 : 2
+     1/0
+     ~~~
    + CategoryInfo          : NotSpecified: (:) [], RuntimeException
    + FullyQualifiedErrorId : RuntimeException

if now I try/catch the error,

[CmdletBinding()]
    param()

process {
    try {
        1/0
    } catch {
        write-error $_
    }
}

I get

Au caractère Ligne:1 : 1
+ U:\test-exception.ps1
+ ~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,test-exception.ps1

where I lose the line number and the line text. I tried many variants but the only way I've found to get the first error message in the error stream of a surrounding CMD while try/catching the code (I want to be able to exit with some custom exit code, not 1) is

[CmdletBinding()]
    param()

process {
    try {
        1/0
    } catch {
        [Console]::Error.WriteLine(($_ | Out-String))
        exit 99
    }
}

did I miss something or is this the only solution?

mklement0 · Accepted Answer · 2022-12-22 22:50:54Z

As you have noticed, when you call Write-Error in a catch block, the error message only shows the origin of the Write-Error call, not the origin of the exception.

You could get the origin of the exception from the PositionMessage property of ErrorRecord.InvocationInfo, but a far easier way is to just pipe the ErrorRecord object ($_) to Out-String.

In addition you may show the script stack trace by querying the ErrorRecord.ScriptStackTrace property, which contains the chain of function calls that led to the error.

Finally, set the ErrorRecord.ErrorDetails property to override the default error message so all the information about the original error will be shown.

try {
    1/0
} catch {
    $_.ErrorDetails = ($_ | Out-String) +
                      "`n------- SCRIPT STACKTRACE -------`n$($_.ScriptStackTrace)" +
                      "`n `n------- CAUGHT AT -------"
    Write-Error $_
}

Output:

C:\Test\ExceptionTest.ps1 : Attempted to divide by zero.
In C:\Test\ExceptionTest.ps1:4 Char:2
+     1/0
+     ~~~
    + CategoryInfo          : NotSpecified: (:) [], RuntimeException
    + FullyQualifiedErrorId : RuntimeException
 
------- SCRIPT STACKTRACE -------
at <ScriptBlock>, C:\Test\ExceptionTest.ps1: Line 4
at <ScriptBlock>, <no file>: Line 1
 
------- CAUGHT AT -------
In Line:1 Char:1
+ . 'C:\Test\ExceptionTest.ps1'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,ExceptionTest.ps1

The information shown after the "CAUGHT AT" line is still pretty useless, but I don't think we can do anything about that, as it is added automatically by PowerShell. At least the relevant information is shown at the top now.

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