Utilize Microsoft.TeamFoundation PowerShell Modules in VSO/VSTS Custom Tasks

If you haven't been paying attention to the "New Microsoft", you may have missed that a lot of their new code is ending up on places like Github. Included in that is the backbone of their new Visual Studio Team Services build and deploy services: tasks.

In exploring the Github repository, I noticed that they were making use of some interesting, non-public modules (primarily in the Microsoft.TeamFoundation.DistributedTask.* namespace). Several of their scripts referenced code like this:

# Import the Task.Common and Task.Internal dll that has all the
cmdlets we need for Build Import-Module
"Microsoft.TeamFoundation.DistributedTask.Task.Internal" Import-Module

In attempting to create my own tasks, I found that I couldn't do that same import. Errors like this would prevent me from utilizing them:

##[error]import-module : Could not load file or assembly 'Microsoft.TeamFoundation.DistributedTask.Agent.Interfaces, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies.
The system cannot find the file specified. At C:\LR\MMS\Services\Mms\TaskAgentProvisioner\Tools \agents\default\tasks\ BuildDnxWebApp\0.1.11\Build-DnxWebApp.ps1:24 char:1
+ import-module "Microsoft.TeamFoundation.DistributedTask.Task.Internal"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Import-Module], FileNotFoundException + FullyQualifiedErrorId : System.IO.FileNotFoundException, + Microsoft.PowerShell.Commands.ImportModuleCommand

After much investigation, I found where the modules live on the VSO/VSTS server. Change your import line to directly reference the agent's module path:

# Import the Task.Common and Task.Internal dll that has all the cmdlets we need for Build
$agentWorkerModulesPath = "$($env:AGENT\_HOMEDIRECTORY)\\agent\\worker\\Modules"
$agentDistributedTaskInternalModulePath = "$agentWorkerModulesPath\\Microsoft.TeamFoundation.DistributedTask.Task.Internal\\Microsoft.TeamFoundation.DistributedTask.Task.Internal.dll"
$agentDistributedTaskCommonModulePath = "$agentWorkerModulesPath\\Microsoft.TeamFoundation.DistributedTask.Task.Common\\Microsoft.TeamFoundation.DistributedTask.Task.Common.dll"
Write-Host "Importing VSTS Module $agentDistributedTaskInternalModulePath"

Import-Module $agentDistributedTaskInternalModulePath
Write-Host "Importing VSTS Module $agentDistributedTaskCommonModulePath"
Import-Module $agentDistributedTaskCommonModulePath

The vital part is the $env:AGENT_HOMEDIRECTORY. This is a predefined variable available to the build runner pointing to the agent's home directory. Underneath this is where the tasks, modules, and other agent-specific assets live. After prefixing the modules with the proper path, I was back in business!

Hopefully this helps someone; I couldn't find a single piece of info on this. Good luck!