[Compute] BREAKING CHANGE: Fix #10728: az vm create: create subnet …

…automatically if vnet is specified and subnet not exists (#12115)

* [Compute] Fix #10728: `az vm create`: create subnet automatically if vnet is specified and subnet not exists

* {Compute} update test_vm_commands to fix merge conflict

* {Compute} fix test recording file for profile hybrid_2018_03_01 & hybrid_2019_03_01

* {Compute} update subnet help message & fail to create error message

* {Compute} update fail to create subnet error message

* {Compute} update test recording due to merge conflict

src/azure-cli/azure/cli/command_modules/vm/_params.py

@@ -677,7 +677,7 @@ def load_arguments(self, _):
         with self.argument_context(scope, arg_group='Network') as c:
             c.argument('vnet_name', help='Name of the virtual network when creating a new one or referencing an existing one.')
             c.argument('vnet_address_prefix', help='The IP address prefix to use when creating a new VNet in CIDR format.')
-            c.argument('subnet', help='The name of the subnet when creating a new VNet or referencing an existing one. Can also reference an existing subnet by ID. If omitted, an appropriate VNet and subnet will be selected automatically, or a new one will be created.')
+            c.argument('subnet', help='The name of the subnet when creating a new VNet or referencing an existing one. Can also reference an existing subnet by ID. If both vnet-name and subnet are omitted, an appropriate VNet and subnet will be selected automatically, or a new one will be created.')
             c.argument('subnet_address_prefix', help='The subnet IP address prefix to use when creating a new VNet in CIDR format.')
             c.argument('nics', nargs='+', help='Names or IDs of existing NICs to attach to the VM. The first NIC will be designated as primary. If omitted, a new NIC will be created. If an existing NIC is specified, do not specify subnet, VNet, public IP or NSG.')
             c.argument('private_ip_address', help='Static private IP address (e.g. 10.0.0.5).')

src/azure-cli/azure/cli/command_modules/vm/custom.py

@@ -660,11 +660,37 @@ def create_vm(cmd, vm_name, resource_group_name, image=None, size='Standard_DS1_
 
         nic_dependencies = []
         if vnet_type == 'new':
-            vnet_name = vnet_name or '{}VNET'.format(vm_name)
             subnet = subnet or '{}Subnet'.format(vm_name)
-            nic_dependencies.append('Microsoft.Network/virtualNetworks/{}'.format(vnet_name))
-            master_template.add_resource(build_vnet_resource(
-                cmd, vnet_name, location, tags, vnet_address_prefix, subnet, subnet_address_prefix))
+            vnet_exists = False
+            if vnet_name:
+                from azure.cli.command_modules.vm._vm_utils import check_existence
+                vnet_exists = \
+                    check_existence(cmd.cli_ctx, vnet_name, resource_group_name, 'Microsoft.Network', 'virtualNetworks')
+                if vnet_exists:
+                    from azure.cli.core.commands import cached_get, cached_put, upsert_to_collection
+                    from azure.cli.command_modules.vm._validators import get_network_client
+                    client = get_network_client(cmd.cli_ctx).virtual_networks
+                    vnet = cached_get(cmd, client.get, resource_group_name, vnet_name)
+
+                    Subnet = cmd.get_models('Subnet', resource_type=ResourceType.MGMT_NETWORK)
+                    subnet_obj = Subnet(
+                        name=subnet,
+                        address_prefixes=[subnet_address_prefix],
+                        address_prefix=subnet_address_prefix
+                    )
+                    upsert_to_collection(vnet, 'subnets', subnet_obj, 'name')
+                    try:
+                        cached_put(cmd, client.create_or_update, vnet, resource_group_name, vnet_name).result()
+                    except Exception:
+                        raise CLIError('Subnet({}) does not exist, but failed to create a new subnet with address '
+                                       'prefix {}. It may be caused by name or address prefix conflict. Please specify '
+                                       'an appropriate subnet name with --subnet or a valid address prefix value with '
+                                       '--subnet-address-prefix.'.format(subnet, subnet_address_prefix))
+            if not vnet_exists:
+                vnet_name = vnet_name or '{}VNET'.format(vm_name)
+                nic_dependencies.append('Microsoft.Network/virtualNetworks/{}'.format(vnet_name))
+                master_template.add_resource(build_vnet_resource(
+                    cmd, vnet_name, location, tags, vnet_address_prefix, subnet, subnet_address_prefix))
 
         if nsg_type == 'new':
             nsg_rule_type = 'rdp' if os_type.lower() == 'windows' else 'ssh'