🚀[Feature]: DSC integration

[FlippingBinary]

Description

This module would fit well in with DSC. Is there any interest in making a class-based DSCv2 resource for this module?

[MariusStorhaug]

Hi Jon Musselwhite (@FlippingBinary)! Just the right size to dip my toe in DSC. Could you tell me more about the use-case and how you would want it to work?

[FlippingBinary]

Sure! I'm pretty new to DSC as well, so I'll discuss it based on my understanding.

In my case, I'm trying to move towards declarative environments so I can easily reinstall the OS and be back into an environment that is optimized for my workflow. DSC also enables me to declare an environment once and apply that configuration on both my desktop and my tablet, which would reduce the annoyance of having one workstation's behavior and capabilities drift from the other during periods of disuse. NerdFonts are a part of that because I use LazyVim and other CLI tools that benefit from the extra icons.

Overview

I imagine a DSC resource for NerdFonts would just ensure a particular font is installed in the scope where it belongs. DSCv3 is what I'm actually using, but it just reached general availability this year so I'm sure there are far more people using DSCv2. Also, DSCv3 resources are only discovered by searching the PATH, but it has a built-in adapter for accessing PS class-based resources. Since this module doesn't seem to have anything else that goes on the PATH and DSCv3 resources don't seem to be backward compatible with DSCv2 configurations, I think making a class-based resource with it would be more beneficial to more people with minimal effort.

Examples

DSCv3 with adapter

An example DSCv3 configuration that I would expect to install 0xProto for all users could be illustrated in a file I'll call font.dsc.yaml:

$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json

resources:
- name: Use PowerShell resources
  type: Microsoft.DSC/PowerShell
  properties:
    resources:
    - name: 0xProto Font
      type: NerdFonts/NerdFont
      properties:
        Name: "0xProto"
        Scope: AllUsers
        Ensure: Present

In this example, the Microsoft.DSC/PowerShell DSCv3 resource is used as an adapter to access a class called NerdFont in the NerdFonts PS module, passing it three properties (although Ensure should default to Present so that it wouldn't be necessary).

If DSC is called with dsc config set --file .\font.dsc.yaml, it would first call the Test method on the NerdFont class. If that returns true, it wouldn't do anything else. If it returns false, it would then call the Set method.

Other examples of DSCv3 configurations can be found in their repository.

DSCv2

A similar example in DSCv2 using the exact same resource (no changes in the module would be needed) could be illustrated in a file I'll call font.ps1:

configuration EnsureFont {
  Import-DscResource -ModuleName NerdFonts

  Node localhost {
    NerdFont FontInstall {
      Name = "0xProto"
      Scope = "AllUsers"
      Ensure = "Present"
    }
  }
}

EnsureFont

Start-DscConfiguration -Path .\EnsureFont -Wait -Verbose -Force

This configuration could be applied by calling .\font.ps1. The EnsureFont line would cause an mof file to be compiled into a directory of the same name, then the Start-DscConfiguration line would ask the local configuration manager to apply the configuration to the host.

Additional considerations

Overlapping scopes

If the configuration is applied when the font is already installed in a smaller scope, it should just install it in the requested scope by default without removing the duplicate. An additional parameter could be used to ensure it's the only scope the font is installed in, perhaps RemoveRedundant: True or something. Similarly, if the font is already installed in a larger scope, it should not install the font in a smaller scope. A parameter like ForceRedundant: True could be used to force it (such as if an unprivileged user needs a font that shares a name with a globally installed one that is the wrong version).

Cross-platform

I haven't explored DSCv3's cross-platform capabilities yet, but it is cross-platform capable. The DSCv3 resources are declared as JSON files that describe how to call CLI tools to get, test, and set configurations. That means the underlying CLI tool can be written in any language and built on any platform. I think the adapter I illustrated above is cross-platform because it calls the cross-platform version of PS.

Comparable implementation

For reference, WinGet's GitDsc module is a good example of a simple DSC resource that clones a repository if it doesn't already exist. Other tools discover it by looking in the module's psd1 file. I believe a NerdFont class would look a lot like that example, calling Get-NerdFont to get or test a configuration and Install-NerdFont to set it.