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Using Plaster To Create a New PowerShell Module

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Chrissy, CK and I presented a pre-con at PASS Summit in Seattle last week

20171031_083328.jpg

Tracey Boggiano T | B came along to our pre-con and afterwards we were talking about creating PowerShell modules. In her blog post she explains how she creates modules by copying the code from another module (dbatools in this case!) and altering it to fit her needs. This is an absolutely perfect way to do things, in our pre-con we mentioned that there is no use in re-inventing the wheel, if someone else has already written the code then make use of it.

I suggested however that she used the PowerShell module Plaster to do this. We didnt have enough time to really talk about Plaster, so Tracy, this is for you (and I am looking forward to your blog about using it to 😉 )

What is Plaster?

Plaster is a template-based file and project generator written in PowerShell. Its purpose is to streamline the creation of PowerShell module projects, Pester tests, DSC configurations, and more. File generation is performed using crafted templates which allow the user to fill in details and choose from options to get their desired output.

How Do I Get Plaster?

The best way to get Plaster is also the best way to get any PowerShell module, from the PowerShell Gallery

You can just run

Install-Module Plaster

If you get a prompt about the repository not being trusted, don’t worry you can say yes.

Following PowerShell’s Security Guiding Principles, Microsoft doesn’t trust its own repository by default. The advice as always is never trust anything from the internet even if a bearded fellow from the UK recommends it!!

The PowerShell Gallery is a centralised repository where anyone can upload code to share and whilst all uploads are analyzed for viruses and malicious code by Microsoft, user discretion is always advised. If you do not want to be prompted every time that you install a module then you can run

Set-PSRepository -Name PSGallery -InstallationPolicy Trusted

if you and/or your organisation think that that is the correct way forward.

What Can We Do With Plaster?

Now that we have installed the module we can get to the nitty gritty. You can (and should) use Plaster to automate the creation of your module structure. If you are going to something more than once then automate it!

I created a repository for my Plaster Template You are welcome to take it and modify it for your own needs. I created a folder structure and some default files that I always want to have in my module folder

module framework.png

So in my template I have created all of the folders to organise the files in the way that I want to for my modules. I have also included the license file and some markdown documents for readme, contributing and installation. If we look in the tests folder

tests folder.png

There are some default test files included as well.

But Plaster is more than just a file and folder template repository, if we look in the installation markdown file,  it looks like this

# Installing <%= $PLASTER_PARAM_ModuleName %>
# You can install <%= $PLASTER_PARAM_ModuleName %> from the Powershell Gallery using
Find-Module <%= $PLASTER_PARAM_ModuleName %> | Install-Module
Import-Module <%= $PLASTER_PARAM_ModuleName %>
We can paramatarise the content of our files. This will create a very simple markdown showing how to find and install the module from the PowerShell Gallery which saves us from having to type the same thing again and again. Lets see how to do that

The Manifest XML file

The magic happens in the manifest file You can create one with the New-PlasterManifest command in the template directory – Thank you to Mustafa for notifying that the manifest file creation now requires an extra parameter of TemplateType

$manifestProperties = @{
Path = "PlasterManifest.xml"
Title = "Full Module Template"
TemplateName = 'FullModuleTemplate'
TemplateVersion = '0.0.1'
TemplateType = 'Item'
Author = 'Rob Sewell'
}
New-Item -Path FullModuleTemplate -ItemType Directory
New-PlasterManifest @manifestProperties
This will create a PlasterManifest.xml file that looks like this
<?xml version="1.0" encoding="utf-8"?>
<plasterManifest
schemaVersion="1.1"
templateType="Project" xmlns="http://www.microsoft.com/schemas/PowerShell/Plaster/v1">
<metadata>
<name>FullModuleTemplate</name>
<id>220fba73-bf86-49e3-9ec5-c4bc2719d196</id>
<version>0.0.1</version>
<title>FullModuleTemplate</title>
<description>My PLaster Template for PowerShell Modules</description>
<author>Rob Sewell</author>
<tags></tags>
</metadata>
<parameters></parameters>
<content></content>
</plasterManifest>
You can see that the parameters and content tags are empty. This is where we will define the parameters which will replace the tokens in our files and the details for how to create our module folder.

Plaster Parameters

At present my parameters tag looks like this
<parameters>
<parameter name="FullName" type="text" prompt="Module author's name" />
<parameter name="ModuleName" type="text" prompt="Name of your module" />
<parameter name="ModuleDesc" type="text" prompt="Brief description on this module" />
<parameter name="Version" type="text" prompt="Initial module version" default="0.0.1" />
<parameter name="GitHubUserName" type="text" prompt="GitHub username" default="${PLASTER_PARAM_FullName}"/>
<parameter name="GitHubRepo" type="text" prompt="Github repo name for this module" default="${PLASTER_PARAM_ModuleName}"/>
</parameters>
So we can set up various parameters with their names and data types defined and a prompt and if we want a default value.
We can then use
<%= $PLASTER_PARAM_WHATEVERTHEPAREMETERNAMEIS %>
in our files to make use of the parameters.

Plaster Content

The other part of the manifest file to create is the content. This tells Plaster what to do when it runs.

Mine is split into 3 parts

<message>
Creating folder structure
</message>
<file source='' destination='docs'/>
<file source='' destination='functions'/>
<file source='' destination='internal'/>
<file source='' destination='tests'/>
We can provide messages to the user with the message tag. I create the folders using the filesource tag
<message>
Deploying common files
</message>
<file source='appveyor.yml' destination=''/>
<file source='contributing.md' destination=''/>
<file source='LICENSE.txt' destination=''/>
<templateFile source='install.md' destination=''/>
<templateFile source='readme.md' destination=''/>
<templateFile source='tests\Project.Tests.ps1' destination=''/>
<templateFile source='tests\Help.Tests.ps1' destination=''/>
<templateFile source='tests\Feature.Tests.ps1' destination=''/>
<templateFile source='tests\Regression.Tests.ps1' destination=''/>
<templateFile source='tests\Unit.Tests.ps1' destination=''/>
<templateFile source='tests\Help.Exceptions.ps1' destination=''/>
<templateFile source='docs\ReleaseNotes.txt' destination=''/>
<file source='module.psm1' destination='${PLASTER_PARAM_ModuleName}.psm1'/>
This part creates all of the required files. You can see that the static files (those which do not require any sort of parameterisation for the contents use the same file source tag as the folders with the source defined. The files that have content which is parameterised use a tag of templateFile Source telling Plaster to look inside there for the tokens to be replaced.
The last part of the content creates the module manifest.
<message>
Creating Module Manifest
</message>
<newModuleManifest
destination='${PLASTER_PARAM_ModuleName}.psd1'
moduleVersion='$PLASTER_PARAM_Version'
rootModule='${PLASTER_PARAM_ModuleName}.psm1'
author='$PLASTER_PARAM_FullName'
description='$PLASTER_PARAM_ModuleDesc'
encoding='UTF8-NoBOM'/>
which I have filled in with the parameters for each of the values.

Creating a new module at the command line

Now you can easily create a module with all of the required folders and files that you want by creating a directory and running

Invoke-Plaster -TemplatePath TEMPLATEDIRECTORY -DestinationPath DESTINATIONDIRECTORY

which looks like this

Its that easy 🙂

Create a module without prompts

You can also create a module without needing to answer prompts. We can prefill them in our parameter splat
$plaster = @{
TemplatePath ="GIT:\PlasterTemplate"
DestinationPath = "GIT:\NewModule"
FullName = "Rob Sewell"
ModuleName = "NewModule"
ModuleDesc = "Here is a module description"
Version = "0.9.0"
GitHubUserName = "SQLDBAWithABeard"
GitHubRepo = "NewModule"
}
If (!(Test-Path $plaster.DestinationPath)) {
New-Item-ItemType Directory -Path $plaster.DestinationPath
}
Invoke-Plaster @plaster
Which will look like this

Make Your Own

Hopefully this have given you enough information and shown you how easy it is to automate creating the framework for your new PowerShell modules and parameterising them. Let me know how you get on and share your examples

Further Reading

Kevin Marquettes blog post is an excellent and detailed post on using Plaster which you should also read for reference as well as David Christians post which has some great content on adding user choice to the parameters enabling one plaster template to fulfill multiple requirements.