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How to get the correct error line number using $ ErrorActionPreference = "Stop"

Consider the following script

#requires -version 2.0

[CmdletBinding()]
param
(
)

$script:ErrorActionPreference = "Stop"
Set-StrictMode -Version Latest
function PSScriptRoot { $MyInvocation.ScriptName | Split-Path }

function ThrowFunction($i)
{
    "ThrowFunction $i"
    $someNonExistingVariable
}

@(1, 2, 3) | ForEach-Object -Process { ThrowFunction $_ }

When we run it we get

C:\dev> .\MyScript.ps1
ThrowFunction 1
ForEach-Object : The variable '$someNonExistingVariable' cannot be retrieved because it has not      been set.
At C:\dev\MyScript.ps1:18 char:28
+ @(1, 2, 3) | ForEach-Object <<<<  -Process { ThrowFunction $_ }
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:Token) [ForEach-Object],     RuntimeException
    + FullyQualifiedErrorId :      VariableIsUndefined,Microsoft.PowerShell.Commands.ForEachObjectCommand

As you can see it reports the problem on line # 18

But the actual problem is line # 15

I found that if we change line 8:

$script:ErrorActionPreference = "Continue"

We get

C:\dev> .\MyScript.ps1
ThrowFunction 1
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At C:\dev\MyScript.ps1:15 char:29
+     $someNonExistingVariable <<<<
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:Token) [], RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined

ThrowFunction 2
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At C:\dev\MyScript.ps1:15 char:29
+     $someNonExistingVariable <<<<
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:Token) [], RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined

ThrowFunction 3
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At C:\dev\MyScript.ps1:15 char:29
+     $someNonExistingVariable <<<<
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:Token) [],     RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined

And you can see that now line 15 is reported as expected.

Now the question is how to get the correct string and have the "Stop" behavior.

I tried many approaches and none of them worked for me.

I tried

trap { throw $_ }

trap { $_.InvocationInfo }

trap { Get-PSCallStack }

but none of them get the correct string

Then I tried to switch

$script:ErrorActionPreference = "Continue"

and found that as soon as I add any trap, the wrong line is reported again.

So, I'm still looking for a job for a solution ...

+3


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3 answers


Thanks to @Keith Hill I found a solution

Magic line

trap { throw $Error[0] }

This script



#requires -version 2.0

[CmdletBinding()]
param
(
)

$script:ErrorActionPreference = "Stop"
Set-StrictMode -Version Latest
function PSScriptRoot { $MyInvocation.ScriptName | Split-Path }

trap { throw $Error[0] }

function ThrowFunction($i)
{
    "ThrowFunction $i"
    $someNonExistingVariable
}

@(1, 2, 3) | ForEach-Object -Process { ThrowFunction $_ }

returns

C:\Dev> .\MyScript.ps1
ThrowFunction 1
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At C:\Dev\MyScript.ps1:17 char:29
+     $someNonExistingVariable <<<<
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:Token) [], RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined

Fine!

+3


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Even if you set strictmode to Latest, it $someNonExistingVariable

will not generate a trailing error. It just writes to the error stream. By setting the ErrorActionPreference to Stop

, you now have a Foreach-Object that converts an endless error to a trailing error. This is why the error indicates line 18 - the Foreach-Object cmdlet.

If you look in the $ Error collection assuming Clear () first, you will see two errors. The latter is at $ Error [0], which is a trailing error thrown by Foreach-Object. $ Error [1] is a non-termination error generated by an attempt to access the undefined variable. It has the correct line number - 15.



You can access the ScriptStackTrace like this:

PS C:\> $error[0].errorRecord.ScriptStackTrace
at ThrowFunction, C:\Users\hillr\ErrorLine.ps1: line 15
at <ScriptBlock>, C:\Users\hillr\ErrorLine.ps1: line 18
at <ScriptBlock>, C:\Users\hillr\ErrorLine.ps1: line 18
+3


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You can try {} Catch {} instead:

#requires -version 2.0

[CmdletBinding()]
param
(
)

$script:ErrorActionPreference = "Stop"
Set-StrictMode -Version Latest
function PSScriptRoot { $MyInvocation.ScriptName | Split-Path }

function ThrowFunction($i)
{
    "ThrowFunction $i"
    Try {
        $someNonExistingVariable
    }
    Catch { # The variable $_ represents the error that is caught
    Write-Output $_
    }
}

@(1, 2, 3) | ForEach-Object -Process { ThrowFunction $_ }

And the resulting output gives the correct line number:

ThrowFunction 1
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At line:16 char:9
+         $someNonExistingVariable
+         ~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:String) [], RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined

ThrowFunction 2
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At line:16 char:9
+         $someNonExistingVariable
+         ~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:String) [], RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined

ThrowFunction 3
The variable '$someNonExistingVariable' cannot be retrieved because it has not been set.
At line:16 char:9
+         $someNonExistingVariable
+         ~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (someNonExistingVariable:String) [], RuntimeException
    + FullyQualifiedErrorId : VariableIsUndefined
0


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