utilities/tools/helper/Get-TemplateDeploymentWhatIf.ps1

<#
.SYNOPSIS
Get a template What-If deployment result using a given parameter file

.DESCRIPTION
Get a template What-If deployment resultusing a given parameter file
Works on a resource group, subscription, managementgroup and tenant level

.PARAMETER parametersBasePath
Mandatory. The path to the root of the parameters folder to test with

.PARAMETER templateFilePath
Mandatory. Path to the template file from root.

.PARAMETER parameterFilePath
Optional. Path to the parameter file from root.

.PARAMETER location
Mandatory. Location to test in. E.g. WestEurope

.PARAMETER resourceGroupName
Optional. Name of the resource group to deploy into. Mandatory if deploying into a resource group (resource group level)

.PARAMETER subscriptionId
Optional. ID of the subscription to deploy into. Mandatory if deploying into a subscription (subscription level) using a Management groups service connection

.PARAMETER managementGroupId
Optional. Name of the management group to deploy into. Mandatory if deploying into a management group (management group level)

.PARAMETER additionalParameters
Optional. Additional parameters you can provide with the deployment. E.g. @{ resourceGroupName = 'myResourceGroup' }

.PARAMETER RepoRoot
Optional. The path to the repository's root

.EXAMPLE
Get-TemplateDeploymentWhatIf -templateFilePath 'C:/key-vault/vault/main.bicep' -parameterFilePath 'C:/key-vault/vault/.test/parameters.json' -location 'WestEurope' -resourceGroupName 'aLegendaryRg'

Get What-If deployment result for the main.bicep of the KeyVault module with the parameter file 'parameters.json' using the resource group 'aLegendaryRg' in location 'WestEurope'

.EXAMPLE
Get-TemplateDeploymentWhatIf -templateFilePath 'C:/key-vault/vault/main.bicep' -location 'WestEurope' -resourceGroupName 'aLegendaryRg'

Get What-If deployment result for the main.bicep of the KeyVault module using the resource group 'aLegendaryRg' in location 'WestEurope'

.EXAMPLE
Get-TemplateDeploymentWhatIf -templateFilePath 'C:/resources/resource-group/main.json' -parameterFilePath 'C:/resources/resource-group/.test/parameters.json' -location 'WestEurope'

Get What-If deployment result for the main.json of the ResourceGroup module with the parameter file 'parameters.json' in location 'WestEurope'
#>
function Get-TemplateDeploymentWhatIf {

    [CmdletBinding(SupportsShouldProcess)]
    param (
        [Parameter(Mandatory)]
        [string] $templateFilePath,

        [Parameter(Mandatory)]
        [string] $location,

        [Parameter(Mandatory = $false)]
        [string] $parameterFilePath,

        [Parameter(Mandatory = $false)]
        [string] $resourceGroupName,

        [Parameter(Mandatory = $false)]
        [string] $subscriptionId,

        [Parameter(Mandatory = $false)]
        [string] $managementGroupId,

        [Parameter(Mandatory = $false)]
        [Hashtable] $additionalParameters,

        [Parameter(Mandatory = $false)]
        [string] $RepoRoot = (Get-Item -Path $PSScriptRoot).parent.parent.parent.FullName
    )

    begin {
        Write-Debug ('{0} entered' -f $MyInvocation.MyCommand)

        # Load helper
        . (Join-Path $repoRoot 'utilities' 'pipelines' 'sharedScripts' 'Get-ScopeOfTemplateFile.ps1')
    }

    process {
        $deploymentNamePrefix = Split-Path -Path (Split-Path $templateFilePath -Parent) -LeafBase
        if ([String]::IsNullOrEmpty($deploymentNamePrefix)) {
            $deploymentNamePrefix = 'templateDeployment-{0}' -f (Split-Path $templateFilePath -LeafBase)
        }

        $modulesRegex = '.+[\\|\/]modules[\\|\/]'
        if ($templateFilePath -match $modulesRegex) {
            # If we can assume we're operating in a module structure, we can further fetch the provider namespace & resource type
            $shortPathElem = (($templateFilePath -split $modulesRegex)[1] -replace '\\', '/') -split '/' # e.g., app-configuration, configuration-store, .test, common, main.test.bicep
            $providerNamespace = $shortPathElem[0] # e.g., app-configuration
            $providerNamespaceShort = ($providerNamespace -split '-' | ForEach-Object { $_[0] }) -join '' # e.g., ac

            $resourceType = $shortPathElem[1] # e.g., configuration-store
            $resourceTypeShort = ($resourceType -split '-' | ForEach-Object { $_[0] }) -join '' # e.g. cs

            $testFolderShort = Split-Path (Split-Path $templateFilePath -Parent) -Leaf  # e.g., common

            $deploymentNamePrefix = "$providerNamespaceShort-$resourceTypeShort-$testFolderShort" # e.g., ac-cs-common
        }

        $DeploymentInputs = @{
            TemplateFile = $templateFilePath
            Verbose      = $true
            OutVariable  = 'ValidationErrors'
        }
        if (-not [String]::IsNullOrEmpty($parameterFilePath)) {
            $DeploymentInputs['TemplateParameterFile'] = $parameterFilePath
        }
        $ValidationErrors = $null

        # Additional parameter object provided yes/no
        if ($additionalParameters) {
            $DeploymentInputs += $additionalParameters
        }

        $deploymentScope = Get-ScopeOfTemplateFile -TemplateFilePath $templateFilePath -Verbose

        # Generate a valid deployment name. Must match ^[-\w\._\(\)]+$
        do {
            $deploymentName = ('{0}-{1}' -f $deploymentNamePrefix, (Get-Date -Format 'yyyyMMddTHHMMssffffZ'))[0..63] -join ''
        } while ($deploymentName -notmatch '^[-\w\._\(\)]+$')

        if ($deploymentScope -ne 'resourceGroup') {
            Write-Verbose "What-If Deployment Test with deployment name [$deploymentName]" -Verbose
            $DeploymentInputs['DeploymentName'] = $deploymentName
        }

        #################
        ## INVOKE TEST ##
        #################
        switch ($deploymentScope) {
            'resourceGroup' {
                if (-not [String]::IsNullOrEmpty($subscriptionId)) {
                    Write-Verbose ('Setting context to subscription [{0}]' -f $subscriptionId)
                    $null = Set-AzContext -Subscription $subscriptionId
                }
                if (-not (Get-AzResourceGroup -Name $resourceGroupName -ErrorAction 'SilentlyContinue')) {
                    if ($PSCmdlet.ShouldProcess("Resource group [$resourceGroupName] in location [$location]", 'Create')) {
                        $null = New-AzResourceGroup -Name $resourceGroupName -Location $location
                    }
                }
                if ($PSCmdlet.ShouldProcess('Resource group level deployment', 'WhatIf')) {
                    $res = New-AzResourceGroupDeployment @DeploymentInputs -WhatIf
                }
                break
            }
            'subscription' {
                if (-not [String]::IsNullOrEmpty($subscriptionId)) {
                    Write-Verbose ('Setting context to subscription [{0}]' -f $subscriptionId)
                    $null = Set-AzContext -Subscription $subscriptionId
                }
                if ($PSCmdlet.ShouldProcess('Subscription level deployment', 'WhatIf')) {
                    $res = New-AzDeployment @DeploymentInputs -Location $Location -WhatIf
                }
                break
            }
            'managementGroup' {
                if ($PSCmdlet.ShouldProcess('Management group level deployment', 'WhatIf')) {
                    $res = New-AzManagementGroupDeployment @DeploymentInputs -Location $Location -ManagementGroupId $ManagementGroupId -WhatIf
                }
                break
            }
            'tenant' {
                Write-Verbose 'Handling tenant level validation'
                if ($PSCmdlet.ShouldProcess('Tenant level deployment', 'WhatIf')) {
                    $res = New-AzTenantDeployment @DeploymentInputs -Location $location -WhatIf
                }
                break
            }
            default {
                throw "[$deploymentScope] is a non-supported template scope"
            }
        }
        if ($ValidationErrors) {
            if ($res.Details) { Write-Warning ($res.Details | ConvertTo-Json -Depth 10 | Out-String) }
            if ($res.Message) { Write-Warning $res.Message }
            Write-Error 'Template is not valid.'
        } else {
            Write-Verbose 'Template is valid' -Verbose
        }
    }

    end {
        Write-Debug ('{0} exited' -f $MyInvocation.MyCommand)
    }
}