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Built-In Directives

Structure and Terminology

The built-in directives for PowerShell consist of three parts:

  • Selector: denoted by the field select, contains the object-type where the modification is taking place. It can be either:

    • command
    • parameter
    • model
    • property

    Note: Depending of the filters, AutoRest infers the type of object that needs to be selected. For example:

      # This selects the parameters
  # ---> where the parameter-name is Foo, and the cmdlet verb is Get
  # ---> sets the parameter alias to Bar
  directive:
    - where:
        verb: Get
        parameter-name: Foo
      set:
        alias: Bar

    A reason to provide the selector would be to change the scope of selection. For example, this would select a command:

      # This selects the cmdlets
  #  ---> where the verb is Get, and where a parameter called Foo exists
  #  ---> sets the parameter alias to VM
  directive:
    - select: command
      where:
        verb: Get
        parameter-name: VirtualMachine
      set:
        alias: Get-VM

  • Filter: denoted by the field where, contains the criteria to select the object.

    • A command can be filtered by:

      • verb
      • subject
      • subject-prefix
      • parameter-name

    • A parameter can be filtered by:

      • parameter-name

      and, optionally by:

      • verb
      • subject
      • subject-prefix

      from the cmdlet it belongs to.

    • A model can be filtered by:

      • model-name
      • property-name

    • A model can be filtered by:

      • property-name

      and, optionally by:

      • model-name

  • Actions: denoted by the fields set, hide, remove and clear-alias. These fields contain the actions to be performed in the selected objects.

Terminology Notes

prefix, subject-prefix and subject

To increase the granularity of cmdlet-tweaking, we divided the cmdlet NOUN into three parts: prefix, subject-prefix and subject. Where:

[verb]-[noun] <-> [verb]-[prefix][subject-prefix][subject]

AutoRest allows you to:

  • Modify the prefix (by default empty)
    • module-wide: using prefix: <value> at the top-level of the configuration document.
  • Modify the subject-prefix (by default empty)
    • module-wide: using subject-prefix: <value> at the top-level of the configuration document.
    • per-cmdlet: using subject-prefix: <value> inside a directive.
  • Modify the subject
    • per-cmdlet: use subject: <value> inside a directive.

variant

A variant is the same thing as the parameter-set name.

hidden cmdlet

When a cmdlet is set to hide: true, the cmdlet will be generated; however, it won't be exported at module-export time.

Directive Scenarios

The following directives cover the most common tweaking scenarios for cmdlet generation:

Note: If you have feedback about these directives, or you would like additional configurations, feel free to open an issue at https://github.com/Azure/autorest.powershell/issues.

Cmdlet Rename

To rename a cmdlet we support both string literals and regex patterns. Cmdlets can be selected and modified by subject-prefix, subject, verb, and/or variant. For example:

# This will rename the cmdlet 'Get-VirtualMachine' (Parameter Set: XYZParamSet) to 'Get-VM'
directive:
  - where:
      verb: Get
      subject: VirtualMachine
      variant: XYZParamSet
    set:
      subject: VM

The following is a Regex example:

# This will change every cmdlet where the subject starts with 'Configuration',
# to have the rest of the subject as Config<rest of the subject>
directive:
  - where:
      subject: (^Configuration)(.*)
    set:
      subject: Config$2

Also, it is possible to select based in a parameter-name. However, to select by parameter, the selector command must be provided. For example:

# This will rename the cmdlet 'Get-VirtualMachine' (Parameter Set: XYZParamSet) to 'Get-VM'
directive:
  - select: command
    where:
      verb: Get
      subject: VirtualMachine
      parameter-name: Id
    set:
      subject: VM

Cmdlet Aliasing

To alias a cmdlet, select the cmdlet and provide an alias:

directive:
  - where:
      verb: Get
      subject: VirtualMachine
    set:
      alias: Get-VM

Or, multiple aliases:

directive:
  - where:
      verb: Get
      subject: VirtualMachine
    set:
      alias:
        - Get-VMachine
        - Get-VM

Cmdlet Suppression

For cmdlet suppression you can either:

  • hide it: by preventing it from being exported at module-export time
  • remove it: by preventing it from being generated

Note: If a cmdlet is hidden, it still can be be used by custom cmdlets.

Cmdlet Hiding (Exportation Suppression)

To hide a cmdlet, you need to provide subject-prefix, subject, verb, and/or variant of the cmdlet --> then set hide: true. For example:

directive:
  - where:
      verb: Update
      subject: Resource
    hide: true

The following is a Regex example:

directive:
  - where:
      subject: PetService.*
    hide: true

Cmdlet Removal

To remove a cmdlet, you need to provide the subject-prefix, subject, verb, and/or variant of the cmdlet ---> then, set remove: true. For example:

directive:
  - where:
      verb: Get
      subject: Operation
    remove: true

The following is a Regex example:

directive:
  - where:
      subject: Config.*
    remove: true

Parameter Rename

To select a parameter you need to provide the parameter-name. Furthermore, if you want to target specific cmdlets you can provide the subject-prefix, subject, verb, and/or variant (i.e. parameter-set). For example:

# This will rename the parameter 'XYZName' from the cmdlet 'Get-Operation' to 'Name'.
directive:
  - where:
      verb: Get
      subject: Operation
      parameter-name: XYZName
    set:
      parameter-name: Name

The following is a Regex example:

# This will rename every parameter that ends with 'Name' to just 'Name'.
directive:
  - where:
      parameter-name: (.*)Name$
    set:
      parameter-name: Name

Parameter Aliasing

To alias a parameter, select the parameter and provide an alias:

directive:
  - where:
      parameter-name: VirtualMachine
    set:
      alias: VM

Or, multiple aliases:

directive:
  - where:
      parameter-name: VirtualMachine
    set:
      alias:
        - VM
        - VMachine

Parameter Hiding

To hide a parameter, select the parameter and provide hide: true:

directive:
  - where:
      verb: Get
      subject: Aks
      parameter-name: VirtualMachine
    hide: true

Note: if the parameter is mandatory, you must provide a default value for it:

directive:
  - where:
      verb: Get
      subject: Aks
      parameter-name: VirtualMachineMandatory
    hide: true
    set:
      default:
        script: '"DefaultVM"'

Parameter Description

To add or modify a parameter description you can use a similar pattern to renaming the parameter, but you need to set parameter-description. For example:

directive:
  - where:
      parameter-name: Name
      verb: Get
      subject: Operation
    set:
      parameter-description: This is the name of the Operation you want to retrieve.

Model Rename

To rename a specific model, provide the name of the model at model-name under where node and the new model name at model-name under the set node. For example:

# This will rename the model name from 'Cat' to 'Gato'.
directive:
  - where:
      model-name: Cat
    set:
      model-name: Gato

The following is a Regex example:

# This will rename every model name that start with 'VirtualMachine' to start with 'VM'.
directive:
  - where:
      model-name: ^VirtualMachine(.*)
    set:
      model-name: VM$1

Model Cmdlet

To generate a cmdlet for a model facilitating users in constructing complex objects, you can choose the model using model-name. The default cmdlet name generated will be New-Az[subject-prefix][model-name]Object, and you can customize it using cmdlet-name. For example:

- model-cmdlet:
  - model-name: Workspace
    cmdlet-name: New-AzWorkspaceObject

Note: If you're working with autorest.powershell v3, the syntax differs, and the cmdlet name cannot be customized. For example:

- model-cmdlet
    - Workspace

Property Rename

To select a property you need to provide the property-name. Furthermore, if you want to target a specific model property, you can provide the model-name. For example:

directive:
  - where:
      model-name: VirtualMachine
      property-name: VirtualMachineName
    set:
      property-name: Name

The following is a Regex example:

directive:
  - where:
      property-name: (.*)Name
    set:
      property-name: Name

Alias Removal

If the option --sanitize-names or --azure is provided, AutoRest will make renames to cmdlets and parameters to remove redundancies. For example in the command Get-VirtualMachine, the parameter VirtualMachineName will be renamed to Name, and aliased to VirtualMachineName. It is possible to eliminate that alias by providing the action clear-alias: true:

directive:
  - where:
      parameter-name: ResourceGroupName
    clear-alias: true

The same can be done with cmdlets.

Table Formatting

This allows you to set the table format for a model. This updates the .format.ps1xml to have the format described below as opposed to the automatic table format that is created at build-time. For example, we are updating the format for a VirtualMachine model to only show the Name and ResourceGroup properties. It updates the column label for ResourceGroup to Resource Group and sets the columns widths for Name and ResourceGroup:

directive:
  - where:
      model-name: VirtualMachine
    set:
      format-table:
        properties:
          - Name
          - ResourceGroup
        labels:
          ResourceGroup: Resource Group
        width:
          Name: 60
          ResourceGroup: 80

Instead of defining an entirely new format for the model, if you'd simply like to remove some properties from the automatic format, you can use:

directive:
  - where:
      model-name: VirtualMachine
    set:
      format-table:
        exclude-properties:
          - Location

This will not work in conjuction with the properties declaration described prior. They are mutually exclusive.

Lastly, if you wish to disable all formatting for the model (remove the automatic format from the .format.ps1xml), you can use:

directive:
  - where:
      model-name: VirtualMachine
    set:
      suppress-format: true

Argument Completers

For parameters, you can declare argument completers that will allow you to tab through the values when entering that parameter interactively. This allows you to declare a PowerShell script that will run to get the values for the completer. For example:

# The script should return a list of values.
directive:
  - where:
      parameter-name: Location
    set:
      completer:
        name: Location Completer
        description: Gets the list of locations available for this resource.
        script: "'westus2', 'centralus', 'global'"

The name and description are optional. They are currently unused properties that may be used in documentation generation in the future.

Default Values

For parameters, you can declare a default value script that will run to set the value for the parameter if it is not provided. Once this is declared for a parameter, that parameter will be made optional at build-time. For example:

# The script should return a value for the parameter.
directive:
  - where:
      parameter-name: SubscriptionId
    set:
      default:
        name: SubscriptionId Default
        description: Gets the SubscriptionId from the current context.
        script: '(Get-AzContext).Subscription.Id'

The name and description are optional. They are currently unused properties that may be used in documentation generation in the future.

Polymorphism

In swagger, polymorphism is recognized as the discriminator keyword. The model with this keyword will be the base class, and the models that use allOf to referece the base class are the child class.

We will use two directives to support polymorphism:

# Disable Inline on the Baseclass(Model)
- no-inline:
  - BaseClass

# Create Model Cmdlets for ChildClasses
- model-cmdlet:
  - model-name: ChildClassA
  - model-name: ChildClassB

As a result, there will be three cmdlets generated:

New-XXXResource -BaseClass <BaseClass> …

New-XXXChildClassAObject …

New-XXXChildClassBObject …

And users normally need two steps to create a resource.

$obj = New-XXXChildClassAObject ... or $obj = New-XXXChildClassBObject …
New-XXXResource -BaseClass $obj …

Custom Input Parameter

To custom input parameters, there are normally three steps:

First of all, we need to add new parameters.

- where:
    subject: subject-name
    variant: variant-name
  add:
    parameters:
      # name and type are required, the others are optional.
      - name: Location
        type: string
        required: true
        completer:
          name: Location Completer
          description: Gets the list of locations available for this resource.
          script: "'westus2', 'centralus', 'global'"
        default:
          name: Location default
          description: This is a default value
        script: "westus2"
        description: "This is a parameter"

Secondly, we should hide original parameters

- where:
    subject: subject-name
    variant: variant-name
    parameter-name: parameter-name
  hide: true

Last, we should provide a way to infer hidden parameters from the new added parameters or other parameters.

For simple cases like 1-1 mapping, we could do it by default directive as below.

- where:
    subject: subject-name
    variant: variant-name
    parameter-name: parameter-name
  set:
    default:
      script: '$name + "test"'
      # set-condition is optional
      set-condition: "$PSBoundParameters.ContainsKey('SubscriptionId')"

For more complicated cases, we may implement it by C# customization.

- where:
    subject: subject-name
    variant: variant-name
  add:
    pipelines:
      input-pipeline:
        - name: customLocation
          # priority is optional, by default it is 100, smaller priority handler will be put in the front of the pipeline.
          priority: 100

After running autorest, autorest will generate a stub C# class as below in custom/input-handlers, and developers should implement the ToDO part according to their requirements.

namespace Microsoft.Azure.PowerShell.Cmdlets.Databricks.Runtime.Cmdlets
{
    public class customLocation : InputHandler
    {
        public override void Process( Microsoft.Azure.PowerShell.Cmdlets.Databricks.Runtime.IContext context)
        {
            // ToDO: Add the custom code here
            NextHandler?.Process(context);
        }
    }
}

Azure PowerShell Specific

For directives that are specific to Azure PowerShell, see https://github.com/Azure/azure-powershell/blob/main/documentation/development-docs/autogen-directives-for-azure-powershell.md