Announcing PowerShell Crescendo 1.1.0-preview01

Jason Helmick

We’re pleased to announce the release of PowerShell Crescendo 1.1.0-preview01. Crescendo is a framework to rapidly develop PowerShell cmdlets for common command line tools, regardless of platform. This preview includes a new schema, support for argument value transformation, the ability to bypass the output handler, and improved error handling.

This is a community driven release built from the many suggestions and requests received directly or from our Github. Thank you PowerShell Community for your adoption and suggestions!

The preview release is now available for download on the PowerShell Gallery.

Installing Crescendo

Requirements:

• Microsoft.PowerShell.Crescendo requires PowerShell 7.0 or higher

To install Microsoft.PowerShell.Crescendo:

Install-Module -Name Microsoft.PowerShell.Crescendo -AllowPreRelease

To install Microsoft.PowerShell.Crescendo using the new PowerShellGet v3:

Install-PSResource -Name Microsoft.PowerShell.Crescendo -AllowPreRelease

Highlighted features

This preview release includes many fixes and suggestions. Here are just a few of the highlights added for this preview.

• Allow for module manifest adaptations (Thanks @tbergstedt)
• Crescendo should offer a way to bypass the output handler (Thanks @potatoqualitee)
• Generated commands cannot handle output written to the error stream (Thanks @draproctor)
• Allow for Parameter values to be translated via key/value pair (Thanks @EmeraldFlame)
• Conversion of input parameter values (Thanks @cdhunt)

New schema version

The Crescendo schema has been updated to include support for two new members to the Parameter class, ArgumentTransform and ArgumentTransformType. The schema works with supported tools like Visual Studio Code to provide intellisense and tooltips during the authoring experience.

URL location of the always-available Crescendo schema:

{
   "$schema": "https://aka.ms/PowerShell/Crescendo/Schemas/2022-06",
   "Commands": []
}

Prevent overwriting of the module manifest

Crescendo creates both the module .psm1 and the module manifest .psd1 when Export-CrescendoModule is executed. This can create problems when you have customized the module manifest beyond the scope of Crescendo. The Export-CrescendoModule cmdlet now provides a NoClobberManifest switch parameter to prevent the manifest from being overwritten.

Export-CrescendoModule -ConfigurationFile .\myconfig.json -ModuleName .\Mymodule -NoClobberManifest

Bypass output handling entirely

Some native commands respond with different output depending on whether the output is sent to the screen or the pipeline. Pastel is an example of a command that changes its output from a graphical screen representation to a single string value when used in a pipeline. Crescendo output handling is pipeline based and can cause these applications to return unwanted results. Crescendo now supports the ability to bypass the output handler entirely.

To bypass all output handling by Crescendo:

"OutputHandlers": [
    {
        "ParameterSetName": "Default",
        "HandlerType": "ByPass"
    }
]

Handling error output

Previously, native command errors weren’t captured by Crescendo and allowed to stream directly to the user. This prevented you from creating enhanced error handling. Crescendo now captures the generated command error output (stderr) and is now available to the output handler. Error messages are placed in a queue. You can access the queue in your output handler using a new function, Pop-CrescendoNativeError.

If you don’t define an output handler, Crescendo uses the default handler. The default output handler ensures that errors respect the -ErrorVariable and -ErrorAction parameters and adds errors to $Error.

Adding an output handler that includes Pop-CrescendoNativeError allows you to inspect errors in the output handler so you can handle them or pass them through to the caller.

"OutputHandlers": [
    {
        "ParameterSetName": "Default",
        "StreamOutput": true,
        "HandlerType": "Inline",
        "Handler": "PROCESS { $_ } END { Pop-CrescendoNativeError -EmitAsError }"
    }
]

Argument value transformation

You may find situations where the input values handed to a Crescendo wrapped command should be translated to a different value for the underlying native command. Crescendo now supports argument transformation to support these scenarios. We updated the schema to add two new members to the Parameter class, ArgumentTransform and ArgumentTransformType. Use these members to transform parameter arguments inline or invoke a script block that takes the parameter value as an argument. The default value for ArgumentTransformType is inline.

Example: Multiplication of a value.

"Parameters": [
    {
        "Name": "mult2",
        "OriginalName": "--p3",
        "ParameterType": "int",
        "OriginalPosition": 2,
        "ArgumentTransform": "param([int]$v) $v * 2"
    }
]

Example: Accepting an ordered hashtable.

"Parameters": [
    {
        "Name": "hasht2",
        "OriginalName": "--p1ordered",
        "ParameterType": "System.Collections.Specialized.OrderedDictionary",
        "OriginalPosition": 0,
        "ArgumentTransform": "param([System.Collections.Specialized.OrderedDictionary]$v) $v.Keys.ForEach({''{0}={1}'' -f $_,$v[$_]}) -join '',''"
    }
]

Example: Argument transformation with join.

"Parameters": [
    {
        "Name": "join",
        "OriginalName": "--p2",
        "ParameterType": "string[]",
        "OriginalPosition": 1,
        "ArgumentTransform": "param([string[]]$v) $v -join '',''"
    }
]

Example: Calling a script based transformation.

"Parameters": [
    {
        "Name" : "Param1",
        "ArgumentTransform": "myfunction",
        "ArgumentTransformType" : "function"
    }
]

More information

To get started using Crescendo, check out the documentation.

Future plans

We value your ideas and feedback and hope you give Crescendo a try. Stop by our GitHub repository and let us know of any issues you find or features you would like added.

Jason Helmick PROGRAM MANAGER 2, Control Plane-JWINTER-OPEX-1010

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