Azure Powershell Workflow : Failed to convert 'System.Activities.InArgument`1[System.String]' to type 'System.String' - azure-powershell

Question

I have a couple of Azure Powershell Workflow runbooks that copy a production database and then run cleanup scripts against it and scale it down to generate dev and stage environemnts. I started getting the error "Failed to convert 'System.Activities.InArgument`1[System.String]' to type 'System.String'" from the parent workbook when I was editing it. I recreated the problem in a set of test runbooks: Test_Child and Test_Parent.
Test_Child is just an empty shell meant to receive a single input string.
workflow Test_Child
{
param(
[parameter(Mandatory=$True)]
[String] $Input
)
}
Test_Parent connects to Azure automation and executes the child workbook. If I run both processes in this order it fails. If I run either one separately or reverse the order of execution it succeeds.
workflow Test_Parent
{
$servicePrincipalConnection=Get-AutomationConnection -Name 'AzureRunAsConnection'
Write-Output "Logging into Azure AD ..."
Connect-AzAccount -Tenant $servicePrincipalConnection.TenantID `
-ApplicationID $servicePrincipalConnection.ApplicationID `
-CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint `
-ServicePrincipal
try
{
Test_Child -Input "input"
}
catch
{
exit
}
}
If I execute the parent runbook I get an error.
Failed
Failed to convert 'System.Activities.InArgument`1[System.String]' to type 'System.String'.
If I remove the runbook call the process completes.
Test_Parent with runbook call removed:
workflow Test_Parent
{
$servicePrincipalConnection=Get-AutomationConnection -Name 'AzureRunAsConnection'
Write-Output "Logging into Azure AD ..."
Connect-AzAccount -Tenant $servicePrincipalConnection.TenantID `
-ApplicationID $servicePrincipalConnection.ApplicationID `
-CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint `
-ServicePrincipal
}
Here is the output:
Logging into Azure AD ...
PSComputerName : localhost
PSSourceJobInstanceId : [My PSSourceJobInstanceId]
Environments : {AzureCloud, AzureUSGovernment, AzureChinaCloud, AzureGermanCloud}
Context : Microsoft.Azure.Commands.Profile.Models.Core.PSAzureContext
If I only call the workbook the process completes as well.
Here is the runbook Test_Parent with the Azure automation connection call removed:
workflow Test_Parent
{
try
{
Test_Child -Input "input"
}
catch
{
exit
}
}
The output
Completed
If I reverse the order of execution it completes.
workflow Test_Parent
{
try
{
Test_Child -Input "input"
}
catch
{
exit
}
$servicePrincipalConnection=Get-AutomationConnection -Name 'AzureRunAsConnection'
Write-Output "Logging into Azure AD ..."
Connect-AzAccount -Tenant $servicePrincipalConnection.TenantID `
-ApplicationID $servicePrincipalConnection.ApplicationID `
-CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint `
-ServicePrincipal
}
Output
Completed
Logging into Azure AD ...
PSComputerName : localhost
PSSourceJobInstanceId : [My PSSourceJobInstanceId]
Environments : {AzureCloud, AzureUSGovernment, AzureChinaCloud, AzureGermanCloud}
Context : Microsoft.Azure.Commands.Profile.Models.Core.PSAzureContext
Any idea why making the automation connection and then executing the workbook creates a data type mismatch error?

Answer 1

I had the exact same problem. In our Test environment the runbooks ran without problem. In our UAT environment, which was set up at a later time, we had the same error as you.
After some investigation I noticed that both environments used a different version of the Az.Accounts module. (2.5.2 in Test, 2.6 in UAT).
After upgrading the Az.Accounts module to 2.7.2 the issue seems to have dissapeared, so i guess it was a bug in the 2.6 version.