ARM Template resourceid() function Fails - azure

Question

Please help me understand what is wrong with my Azure ARM template here, Which is very basic, takes some input arguments and prints out resourceId.
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"virtualNetworkName": {
"type": "string"
},
"virtualNetworkResourceGroupName": {
"type": "string"
},
"subnetName": {
"type": "string"
},
"location": {
"type": "string",
"metadata": {
"description": "Location to Deploy Azure Resources"
}
}
},
"resources": [],
"outputs": {
"subnetRef": {
"type": "string",
"value": "[resourceId(parameters('virtualNetworkResourceGroupName'), 'Microsoft.Network/virtualNetworks/subnets', parameters('virtualNetworkName'), parameters('subnetName'))]"
}
}
}
Providing the required parameters, it fails with the following Error Message.
Parameter File
{
"$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"virtualNetworkName": {
"value": "core-services-vnet"
},
"virtualNetworkResourceGroupName": {
"value": "core-networking-rg"
},
"subnetName": {
"value": "private"
},
"location": {
"value": "westus"
}
}
}
$ az deployment create -n core-deploy --template-file azuredeploy.json --parameters #params.json --location westus
Deployment failed. Correlation ID: b97a7544-2814-40c0-88c9-fbaaea2bf645. The template output 'subnetRef' is not valid: The provided value 'core-networking-rg' is not valid subscription identifier. Please see https://aka.ms/arm-template-expressions/#resourceid for usage details.
What Am I missing here ?
Thanks, Nag

Answer 1

The problem is the deployment scope. You can target your deployment to either an Azure subscription or a resource group within a subscription.
In your template, the $schema https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json# is used for resource group deployments, while the commands az deployment create you use is for subscription-level deployments. The schema https://schema.management.azure.com/schemas/2018-05-01/subscriptionDeploymentTemplate.json# for subscription-level deployments is different than the schema for resource group deployments. You could get references from creating resource groups and resources at the subscription level.
In this case, you can use the commands az group deployment create -n core-deploy --template-file azuredeploy.json --parameters #params.json --location westus instead of az deployment create xxx to fix this issue.