Azure: Don't provide location for build_resource_group_name

Location is required by default because you must specify where to create
the resource group containing the packer resources.

When using build_resource_group_name you are specifying that packer
should use an existing resource group and so the location that resources
are in can be determined by fetching the information from the existing
group.

It is forbidden to pass both variables as it is easier and more
intuitive that the location comes from the group rather than ignore a
parameter.

Closes: #5655

builder/azure/arm/builder.go

@@ -103,6 +103,15 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		}
 	}
 
+	if b.config.BuildResourceGroupName != "" {
+		group, err := azureClient.GroupsClient.Get(b.config.BuildResourceGroupName)
+		if err != nil {
+			return nil, fmt.Errorf("Cannot locate the existing build resource resource group %s.", b.config.BuildResourceGroupName)
+		}
+
+		b.config.Location = *group.Location
+	}
+
 	if b.config.StorageAccount != "" {
 		account, err := b.getBlobAccount(azureClient, b.config.ResourceGroupName, b.config.StorageAccount)
 		if err != nil {
@@ -290,7 +299,6 @@ func (b *Builder) configureStateBag(stateBag multistep.StateBag) {
 		stateBag.Put(constants.ArmKeyVaultDeploymentName, fmt.Sprintf("kv%s", b.config.tmpDeploymentName))
 	}
 	stateBag.Put(constants.ArmKeyVaultName, b.config.tmpKeyVaultName)
-	stateBag.Put(constants.ArmLocation, b.config.Location)
 	stateBag.Put(constants.ArmNicName, DefaultNicName)
 	stateBag.Put(constants.ArmPublicIPAddressName, DefaultPublicIPAddressName)
 	if b.config.TempResourceGroupName != "" && b.config.BuildResourceGroupName != "" {
@@ -312,6 +320,7 @@ func (b *Builder) configureStateBag(stateBag multistep.StateBag) {
 
 // Parameters that are only known at runtime after querying Azure.
 func (b *Builder) setRuntimeParameters(stateBag multistep.StateBag) {
+	stateBag.Put(constants.ArmLocation, b.config.Location)
 	stateBag.Put(constants.ArmManagedImageLocation, b.config.manageImageLocation)
 }
 

builder/azure/arm/builder_test.go

@@ -20,7 +20,6 @@ func TestStateBagShouldBePopulatedExpectedValues(t *testing.T) {
 		constants.ArmTags,
 		constants.ArmComputeName,
 		constants.ArmDeploymentName,
-		constants.ArmLocation,
 		constants.ArmNicName,
 		constants.ArmResourceGroupName,
 		constants.ArmStorageAccountName,

builder/azure/arm/config.go

@@ -590,10 +590,6 @@ func assertRequiredParametersSet(c *Config, errs *packer.MultiError) {
 		}
 	}
 
-	if c.Location == "" {
-		errs = packer.MultiErrorAppend(errs, fmt.Errorf("A location must be specified"))
-	}
-
 	/////////////////////////////////////////////
 	// Deployment
 	xor := func(a, b bool) bool {
@@ -604,6 +600,10 @@ func assertRequiredParametersSet(c *Config, errs *packer.MultiError) {
 		errs = packer.MultiErrorAppend(errs, fmt.Errorf("Specify either a VHD (storage_account and resource_group_name) or Managed Image (managed_image_resource_group_name and managed_image_name) output"))
 	}
 
+	if !xor(c.Location != "", c.BuildResourceGroupName != "") {
+		errs = packer.MultiErrorAppend(errs, fmt.Errorf("Must specify either a location to create the resource group in or an existing build_resource_group_name."))
+	}
+
 	if c.ManagedImageName == "" && c.ManagedImageResourceGroupName == "" {
 		if c.StorageAccount == "" {
 			errs = packer.MultiErrorAppend(errs, fmt.Errorf("A storage_account must be specified"))

builder/azure/arm/config_test.go

@@ -972,6 +972,7 @@ func TestConfigShouldRejectInvalidResourceGroupNames(t *testing.T) {
 			}
 		}
 
+		delete(config, "location") // not valid for build_resource_group_name
 		delete(config, x)
 	}
 }

website/source/docs/builders/azure.html.md

@@ -44,10 +44,6 @@ builder.
 
     CLI example `azure vm image list-skus -l westus -p Canonical -o UbuntuServer`
 
--   `location` (string) Azure datacenter in which your VM will build.
-
-    CLI example `azure location list`
-
 #### VHD or Managed Image
 
 The Azure builder can create either a VHD, or a managed image. If you
@@ -77,14 +73,42 @@ When creating a managed image the following two options are required.
      set. See [documentation](https://docs.microsoft.com/en-us/azure/storage/storage-managed-disks-overview#images) to
      learn more about managed images.
 
+#### Resource Group Usage
+
+The Azure builder can either provision resources into a new resource group that
+it controls (default) or an existing one.  The advantage of using a packer
+defined resource group is that failed resource cleanup is easier because you
+can simply remove the entire resource group, however this means that the
+provided credentials must have permission to create and remove resource groups.
+By using an existing resource group you can scope the provided credentials to
+just this group, however failed builds are more likely to leave unused
+artifacts.
+
+To have packer create a resource group you **must** provide:
+
+-   `location` (string) Azure datacenter in which your VM will build.
+
+    CLI example `azure location list`
+
+and optionally:
+
+-   `temp_resource_group_name` (string) name assigned to the temporary resource
+    group created during the build.  If this value is not set, a random value will
+    be assigned. This resource group is deleted at the end of the build.
+
+To use an existing resource group you **must** provide:
+
+-   `build_resource_group_name` (string) - Specify an existing resource group
+    to run the build in.
+
+Providing `temp_resource_group_name` or `location` in combination with `build_resource_group_name` is not allowed.
+
 ### Optional:
 
 -   `azure_tags` (object of name/value strings) - the user can define up to 15 tags. Tag names cannot exceed 512
     characters, and tag values cannot exceed 256 characters. Tags are applied to every resource deployed by a Packer
     build, i.e. Resource Group, VM, NIC, VNET, Public IP, KeyVault, etc.
 
--   `build_resource_group_name` (string) - Specify an existing resource group to run the build in. Cannot be used together with `temp_resource_group_name` and requires less permissions due to not creating or destroying a resource group.
-
 -   `cloud_environment_name` (string) One of `Public`, `China`, `Germany`, or
     `USGovernment`. Defaults to `Public`. Long forms such as
     `USGovernmentCloud` and `AzureUSGovernmentCloud` are also supported.
@@ -134,10 +158,6 @@ When creating a managed image the following two options are required.
     assigned.  Knowing the resource group and VM name allows one to execute commands to update the VM during a Packer
     build, e.g. attach a resource disk to the VM.
 
--   `temp_resource_group_name` (string) name assigned to the temporary resource group created during the build.  If this
-    value is not set, a random value will be assigned. This resource group is deleted at the end of the build. Cannot be
-    used together with `build_resource_group_name`.
-
 -   `tenant_id` (string) The account identifier with which your `client_id` and `subscription_id` are associated. If not
     specified, `tenant_id` will be looked up using `subscription_id`.