PSDepend

This is a simple PowerShell dependency handler. You might loosely compare it to bundle install in the Ruby world or pip install -r requirements.txt in the Python world.

PSDepend allows you to write simple *.depend.psd1 or requirements.psd1 files that describe what dependencies you need, which you can invoke with Invoke-PSDepend

WARNING:

• Opening this up quite early to get feedback and direction. There will be breaking changes without notice until we hit version 0.1.0
• Minimal to no testing. This is in my backlog, but PRs would be welcome!
• This borrows quite heavily from PSDeploy. There may be leftover components that haven't been adapted, or have been improperly adapted
• Would love ideas, feedback, pull requests, etc., but if you rely on this, consider pinning a specific version to avoid hitting breaking changes.

Defining Dependencies

Store dependencies in a PowerShell data file, and use *.depend.psd1 or requirements.psd1 to allow Invoke-PSDepend to find your files for you.

What does a dependency file look like?

Simple syntax

Here's the simplest syntax. If this meets your needs, you can stop here:

@{
    psake        = 'latest'
    Pester       = 'latest'
    BuildHelpers = '0.0.20'  # I don't trust this Warren guy...
    PSDeploy     = '0.1.21'  # Maybe pin the version in case he breaks this...
    
    RamblingCookieMonster/PowerShell = 'master'
}

And what PSDepend sees:

DependencyName                   DependencyType  Version Tags
--------------                   --------------  ------- ----
psake                            PSGalleryModule latest      
BuildHelpers                     PSGalleryModule 0.0.20      
Pester                           PSGalleryModule latest      
RamblingCookieMonster/PowerShell Git             master      
PSDeploy                         PSGalleryModule 0.1.21   

There's a bit more behind the scenes - we assume you want PSGalleryModules or GitHub repos unless you specify otherwise, and we hide a few dependency properties.

Flexible syntax

What else can we put in a dependency? Here's an example using a more flexible syntax. You can mix and match.

@{
    psdeploy = 'latest'

    buildhelpers_0_0_20 = @{
        Name = 'buildhelpers'
        DependencyType = 'PSGalleryModule'
        Parameters = @{
            Repository = 'PSGallery'
        }
        Version = '0.0.20'
        Tags = 'prod', 'test'
        PreScripts = 'C:\RunThisFirst.ps1'
        DependsOn = 'some_task'
    }

    some_task = @{
        DependencyType = 'task'
        Target = 'C:\RunThisFirst.ps1'
        DependsOn = 'nuget'
    }

    nuget = @{
        DependencyType = 'FileDownload'
        Source = 'https://dist.nuget.org/win-x86-commandline/latest/nuget.exe'
        Target = 'C:\nuget.exe'
    }  
}

This example illustrates using a few different dependency types, using DependsOn to sort things (e.g. some_task runs after nuget), tags, and other options.

You can inspect the full output as needed. For example:

# List the dependencies, get the third item, show all props
$Dependency = Get-Dependency \\Path\To\complex.depend.ps1
$Dependency[2] | Select *

DependencyFile : \\Path\To\complex.depend.psd1
DependencyName : buildhelpers_0_0_20
DependencyType : PSGalleryModule
Name           : buildhelpers
Version        : 0.0.20
Parameters     : {Repository}
Source         : 
Target         : 
AddToPath      : 
Tags           : {prod, test}
DependsOn      : some_task
PreScripts     : C:\RunThisFirst.ps1
PostScripts    : 
Raw            : {Version, Name, Tags, DependsOn...}

Exploring and Getting Help

Each DependencyType - PSGalleryModule, FileDownload, Task, etc. - might treat these standard properties differently, and may include their own Parameters. For example, in the BuildHelpers node above, we specified a Repository parameter.

How do we find out what these mean? First things first, let's look at what DependencyTypes we have available:

Get-PSDependType

DependencyType  Description                                                 DependencyScript                                    
--------------  -----------                                                 ----------------                                    
PSGalleryModule Install a PowerShell module from the PowerShell Gallery.    C:\...\PSDepend\PSDepen...
Task            Support dependencies by handling simple tasks.              C:\...\PSDepend\PSDepen...
Noop            Display parameters that a depends script would receive...   C:\...\PSDepend\PSDepen...
FileDownload    Download a file                                             C:\...\PSDepend\PSDepen...

Now that we know what types are available, we can read the comment-based help. Hopefully the author took their time to write this:

Get-PSDependType -DependencyType PSGalleryModule -ShowHelp

...
DESCRIPTION
    Installs a module from a PowerShell repository like the PowerShell Gallery.

    Relevant Dependency metadata:
        Name: The name for this module
        Version: Used to identify existing installs meeting this criteria, and as RequiredVersion for installation.  Defaults to 'latest'
        Target: Used as 'Scope' for Install-Module.  If this is a path, we use Save-Module with this path.  Defaults to 'AllUsers'

PARAMETERS
...
    -Repository <String>
        PSRepository to download from.  Defaults to PSGallery

In this example, we see how PSGalleryModule treats the Name, Version, and Target in a depend.psd1, and we see a Parameter specific to this DependencyType, 'Repository'

Finally, we have a few about topics, and individual commands have built in help:

Get-Help about_PSDepend
Get-Help about_PSDepend_Definitions
Get-Help Get-Dependency -Full

Notes

Major props to Michael Willis for the idea - check out his PSRequire, a similar but more feature-full solution.