Remove-AzDenyAssignment: throws on delete-of-missing instead of being idempotent (also has //subscriptions/ slash bug)

[jruttle]

Description

Remove-AzDenyAssignment throws when invoked against a deny assignment that does not exist. The underlying REST API returns 204 No Content (idempotent delete), so the cmdlet should return silently.

The error message also exposes a double-slash bug in the scope string used in the error text:

No deny assignment named '<guid>' found at scope '//subscriptions/<sub>'.
                                                  ^^ note the double slash

Repro

Tested against the Debug build from PR #29340 (Az.Resources 9.0.3).

Import-Module C:\src\azure-powershell\artifacts\Debug\Az.Resources\Az.Resources.psd1 -Force
Connect-AzAccount -Tenant <tenant> -Subscription <sub>

$bogusId = [guid]::NewGuid().ToString()
Remove-AzDenyAssignment -DenyAssignmentName $bogusId -Scope "/subscriptions/<sub>"
# -> Confirm prompt appears (see Bug A)
# -> After Y: "No deny assignment named '<guid>' found at scope '//subscriptions/<sub>'."

Confirm REST is idempotent:

$token = (Get-AzAccessToken).Token
Invoke-WebRequest -Method DELETE `
  -Uri "https://management.azure.com/subscriptions/<sub>/providers/Microsoft.Authorization/denyAssignments/$bogusId?api-version=2024-07-01-preview" `
  -Headers @{ Authorization = "Bearer $token" } `
  -SkipHttpErrorCheck | Select-Object StatusCode
# -> 204

Expected

Cmdlet returns silently when the DA does not exist (matching REST 204 idempotent behavior, and matching e.g. Remove-AzRoleAssignment behavior). Optionally: emit a verbose/warning message but do not throw.

Actual

Cmdlet throws a terminating error claiming the DA was not found, even though delete-of-missing is contractually a no-op. The error text also has a duplicate / in the scope string indicating a path-construction bug.

Impact

• Cleanup scripts and idempotent automation cannot use Remove-AzDenyAssignment without a try/catch
• Inconsistent with REST contract and with Remove-AzRoleAssignment
• Double-slash in error message indicates deeper scope-handling issue (may also affect other code paths)

Related

• PR Add New-AzDenyAssignment and Remove-AzDenyAssignment cmdlets #29340 introduced *-AzDenyAssignment cmdlets
• See companion bugs: -Confirm:$false ignored; List\1` overload error after confirm

[jruttle]

Closing — filed in error. Will be addressed via a follow-up PR by the original author of PR #29340.