Bonus Argument Completers For Azure

SubscriptionNameCompleterAttribute.ps1

using namespace Microsoft.Azure.Commands.Common.Authentication.Abstractions
using namespace System.Management.Automation.Language
using namespace System.Management.Automation
using namespace System.Collections.Generic
using namespace System.Collections

[AttributeUsage("Property,Field")]
class SubscriptionNameCompleter : ArgumentCompleterAttribute {
    # PowerShell expects you to write IArgumentCompleter and register them with this syntax:
    #     [ArgumentCompleter([MyIArgumentCompleter])]
    # Or to use scriptblocks with:
    #     [ArgumentCompleter({ code })]

    # Here, we combine an override for Argumentcompleter with the second syntax, meaning this can be used like:
    #     [SubscriptionNameCompleter()]
    # Or as a parameter to RegisterArgumentCompleter, like this:
    #     Get-Command -Module Az.* -ParameterName SubscriptionName | % {
    #         Register-ArgumentCompleter -Command $_.Name -ParameterName SubscriptionName -ScriptBlock ([SubscriptionNameCompleter]::GetCompleter())
    #     }
    SubscriptionNameCompleter() : base([scriptblock][SubscriptionNameCompleter]::GetCompleter()) {}

    [scriptblock] static GetCompleter() {
         return {
            param([String]$commandName, [String]$parameterName, [String]$wordToComplete, [CommandAst]$commandAst, [IDictionary]$fakeBoundParameter)
            # This test ensures this tab completer doesn't crash when the assembly dependency isn't loaded
            if (($Provider = "Microsoft.Azure.Commands.Common.Authentication.Abstractions.AzureRmProfileProvider" -as [Type])) {
                # In this tab completer, we're relying on the stuff inside the Azure module for tab completers...
                $Provider::Instance.Profile.Subscriptions.Where({
                    # Note this is NOT the normal Where method, it's a LINQ filter (thus, $Args[0] instead of $_)
                    ($null -ne $args[0]) -and
                    ($args[0].ExtendedProperties["Account"] -eq $Provider::Instance.Profile.DefaultContext.Account.Id) -and
                    ($args[0].Name -Like "*$wordToComplete*")
                }).ForEach({
                    $ListItemText = $_.Name
                    # For extra credit: Highlighting the ListItemText for the default value makes it sort first!
                    if ($_.Id -eq $Provider::Instance.Profile.DefaultContext.Subscription.Id) {
                        $ListItemText = "$([char]27)[96m$($ListItemText)$([char]27)[39m"
                    }
                    # More extra credit: The tooltip (and the ListItemText) show up in PSReadLine's Ctrl+Space UX:
                    $Tooltip = ($_ | Format-List Name,
                        @{N = "Account"; E = { $_.ExtendedProperties["Account"] } },
                        @{N = "Environment"; E = { $_.ExtendedProperties["Environment"] } },
                        @{N = "Enabled"; E = { $_.State -eq "Enabled"}} | Out-String -Stream).ForEach("Trim") -join "`n"

                     # The actual things we output are CompletionResults
                    [CompletionResult]::new("'$($_.Name)'", $ListItemText, 'ParameterValue', $Tooltip)
                }) | Sort-Object ListItemText
            }
        }
    }
}