Extract subscription ID, resource group name, and resource name from resource ID?

[SvenAelterman]

I know there are some open issues for creating new functions that can reference existing resources using their resource ID.

In the meantime, if I have a resource ID as a parameter (I would know which resource type it is), can I extract the subscription ID, resource group, and resource name from a resource ID string so I can define it as an existing resource?

[SvenAelterman]

This is a workaround I currently use, but it feels brittle:

var vnetIdSplit = split(virtualNetworkId, '/')
var vnetResourceGroupName = vnetIdSplit[4]
var vnetName = last(vnetIdSplit)

resource vnetResourceGroup 'Microsoft.Resources/resourceGroups@2021-04-01' existing = {
  name: vnetResourceGroupName
  scope: subscription()
}

resource vnet 'Microsoft.Network/virtualNetworks@2022-05-01' existing = {
  name: vnetName
  scope: vnetResourceGroup
}

resource subnet 'Microsoft.Network/virtualNetworks/subnets@2022-05-01' existing = {
  name: subnetName
  parent: vnet
}

[rebuildtech]

Can you please elobarate your question?

You wanted to pull out resource ID from a specific resource ?

You can always do that using output in BICEP

for example

resource function 'Microsoft.web/sites@01-03-2022' = {
name = functionName
}

output functionResourceId = function.id

Let me know if there is anything else that you are looking out for ?

[SvenAelterman]

Hi @rebuildtech,
What I am really trying to accomplish is create a symbolic reference to an existing resource. What I have (as input to a module) is a full resource ID.
It's not currently possible to define an existing resource using a full resource ID. So, I am looking for a method to parse that into its component pieces, such as the subscription, resource group, and resource name.
The split function works, but because it relies on hardcoding the array index of each element, it feels brittle.

[brwilkinson]

@SvenAelterman I think what you have there is the best option we have.

There may be a related issue for this, if I can find It I will link it.

For role assignments on a resource scope... there is a workaround here:

• https://github.com/brwilkinson/AzureDeploymentFramework/blob/main/ADF/bicep/x.RBAC-ALL.bicep
• https://github.com/brwilkinson/AzureDeploymentFramework/blob/main/ADF/bicep/x.RBAC-ALL-RA-Resource.bicep
• https://github.com/brwilkinson/AzureDeploymentFramework/blob/main/ADF/bicep/loadTextContext/genericRoleAssignment.json

The above flow ends up using ARM JSON, which was more open and had an option to provide a scope which was a resourceid. This was removed in Bicep to enable better type checking and resource referencing in a more robust way. It did leave this small gap in functionality.

• As I mentioned I will try link the issue if I can find it, here are a few, however there is one other I am looking for.
  • Look up existing resources by properties other than name #4917
  • Proposal - simplifying resource referencing (part 2) #2246
  • Snippet improvements #2247

[gbonk]

For what its worth, I believe that @SvenAelterman is asking for a feature that Terraform added a year or two ago.

https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/functions/parse_resource_id

I'm fairly new to Bicep and I just ran into looking for this feature as well.

For example, I have this module... private-endpoint.bicep

param name string
param location string

param serviceConnectionName string
param serviceConnectionResourceId string
param subnetResourceId string

resource privateEndpoint 'Microsoft.Network/privateEndpoints@2023-09-01' = {
  name: name
  location: location
  properties: {
    privateLinkServiceConnections: [
      {
        name: serviceConnectionName 
        properties: {
          privateLinkServiceId: serviceConnectionResourceId 
          groupIds: [
            'vault' // Group ID for Key Vault
          ]
        }
      }
    ]
    subnet: {
      id: subnetResourceId
    }
  }
}

Our corporate naming standard says to use the name of the resource taken from the serviceConnectionResourceId.
It would be nice to not have to either pass in separately the serviceConnectionName or to try to parse the passed in serviceConnectionResourceId

Therefore, if i had a func parseResourceId( resourceId string) object => {..} I could have safe means to get the parts of a resourceId

var parsedResourceId = parseResourceId("/subscriptions/12345678-1234-9876-4563-123456789012/resourceGroups/resGroup1/providers/Microsoft.KeyVault/vaults/myuniquevaultname123")

where the var parsedResourceId would be an object with value like...

{
  resourceGroupName: 'resGroup1'
  resourceName: = 'myuniquevaultname123'
  resourceProvider:  = 'Microsoft.KeyVault'
  subscriptionId: '12345678-1234-9876-4563-123456789012'
  fullResourceType: 'Microsoft.KeyVault/vaults'
 }

Having a function makes the extended resource IDs easier to parse and handle as well. Say we have a subnet , /subscriptions/YOUR_SUBSCRIPTION_ID/resourceGroups/YOUR_RESOURCE_GROUP_NAME/providers/Microsoft.Network/virtualNetworks/YOUR_VIRTUAL_NETWORK_NAME/subnets/YOUR_SUBNET_NAME

because this is a subnet and not a vnet I would prefer something like...

{
  resourceGroupName: 'YOUR_RESOURCE_GROUP_NAME'
  resourceName: = 'YOUR_SUBNET_NAME'
  resourceProvider:  = 'Microsoft.Network/virtualNetworks'
  subscriptionId: 'YOUR_SUBSCRIPTION_ID'
  fullResourceType: 'Microsoft.Network/virtualNetworks/subnets'
 }

A parseResourceId function also would make it easier to have a lookup function for the groupIds too.