Call Build vNext task directly

Question

Build vNext tasks are an awesome improvement over the previous build process. One downside though is that I can't make some tasks conditional. I can create an additional build for every combination, but this clearly scales badly and causes lots of additional work if we have to change some other part of the build.

Instead I'd prefer being able to write my own PowerShell tasks that can call existing build tasks. There is at least one downside to this (if no build asks specifically for the vso-task the build agent won't download it), but considering we are using on-premise TFS and build agents I can live with this.

I tried to do something like the following:

$path = get-item "$env:AGENT_HOMEDIRECTORY\Tasks\NuGetPackager\0.1.56\NuGetPackager.ps1"
& "$path" -searchPattern $searchPattern -outputDir "$packageFolder" -configurationToPackage $configurationToPackage -nugetAdditionalArgs "$nugetAdditionalArgs -version $nugetVersion"

Sadly this causes the following error:

2016-04-12T09:50:22.3652811Z ##[error]import-module : Could not load file or assembly 'Microsoft.TeamFoundation.DistributedTask.Agent.Interfaces,  
2016-04-12T09:50:22.3652811Z ##[error]Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find 
2016-04-12T09:50:22.3652811Z ##[error]the file specified.
2016-04-12T09:50:22.3652811Z ##[error]At C:\Agent1\Tasks\NuGetPackager\0.1.56\NuGetPackager.ps1:19 char:1

Now one solution I found on the web indicates that I could add the looked for dlls to the GAC, but I really, really don't want to. Also clearly the tasks work just fine when called from TFS directly, so what configuration am I missing?

I tried adding the folder containing the dlls to the path and even call SetDllDirectory explicitly in the PowerShell, but neither of those help.

Environment: Windows Server 2012 R2 on both build agent and TFS server. TFS 2015 Update 1.

jessehouwing jessehouwing · Accepted Answer · 2016-04-14T14:21:30

The Powershell task Host that's used by the build agent for 2015 RTM up to Update 2 is a custom host which does creative things to resolve assemblies and handle input/output. These tasks can't be called from outside the agent.

Plus, quite a few build tasks are implemented using Node, so you'll have to detect which one is which and invoke them accordingly.

The build tasks are being migrated to a new vsts-task-lib, which will support out-of-agent invocation. These would allow exactly what you want.

In the mean time you could take the existing tasks (they're a simple manifest plus script in most cases) and add one string parameter to the task in which you stick a variable which you can then treat as the condition. You'd need to replace all the standard tasks. Then push them again. if you keep the ExtensionID and the Task GUID the same, they'll act as in-place replacements. This is probably the easiest way to do what you want without having to perform all kinds of hacks that take away the Task's UI. Just set the version number to something ridiculously higher, like 100.0.1.83. that way you'll always end up using your version.

Note: the new builds are meant to be repeatable, in that calling the same build multiple times they always yield the same results. conditional actions can be captured in custom powershell scripts that are stored in source control. These can be executed as part of the workflow.

Call Build vNext task directly

1 Answers