New Data Source: azurerm_monitor_diagnostic_categories

Tests pass:

```
$ acctests azurerm TestAccDataSourceArmMonitorDiagnosticCategories_
=== RUN   TestAccDataSourceArmMonitorDiagnosticCategories_appService
--- PASS: TestAccDataSourceArmMonitorDiagnosticCategories_appService (150.71s)
=== RUN   TestAccDataSourceArmMonitorDiagnosticCategories_storageAccount
--- PASS: TestAccDataSourceArmMonitorDiagnosticCategories_storageAccount (108.97s)
PASS
ok  	github.com/terraform-providers/terraform-provider-azurerm/azurerm	261.573s
```

azurerm/data_source_monitor_diagnostic_categories.go

@@ -0,0 +1,89 @@
+package azurerm
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/Azure/azure-sdk-for-go/services/preview/monitor/mgmt/2018-03-01/insights"
+	"github.com/hashicorp/terraform/helper/schema"
+	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/helpers/azure"
+)
+
+func dataSourceArmMonitorDiagnosticCategories() *schema.Resource {
+	return &schema.Resource{
+		Read: dataSourceArmMonitorDiagnosticCategoriesRead,
+		Schema: map[string]*schema.Schema{
+			"resource_id": {
+				Type:         schema.TypeString,
+				Required:     true,
+				ValidateFunc: azure.ValidateResourceID,
+			},
+
+			"logs": {
+				Type:     schema.TypeSet,
+				Elem:     &schema.Schema{Type: schema.TypeString},
+				Set:      schema.HashString,
+				Computed: true,
+			},
+
+			"metrics": {
+				Type:     schema.TypeSet,
+				Elem:     &schema.Schema{Type: schema.TypeString},
+				Set:      schema.HashString,
+				Computed: true,
+			},
+		},
+	}
+}
+
+func dataSourceArmMonitorDiagnosticCategoriesRead(d *schema.ResourceData, meta interface{}) error {
+	categoriesClient := meta.(*ArmClient).monitorDiagnosticSettingsCategoryClient
+	ctx := meta.(*ArmClient).StopContext
+
+	actualResourceId := d.Get("resource_id").(string)
+	// trim off the leading `/` since the CheckExistenceByID / List methods don't expect it
+	resourceId := strings.TrimPrefix(actualResourceId, "/")
+
+	// then retrieve the possible Diagnostics Categories for this Resource
+	categories, err := categoriesClient.List(ctx, resourceId)
+	if err != nil {
+		return fmt.Errorf("Error retrieving Diagnostics Categories for Resource %q: %+v", actualResourceId, err)
+	}
+
+	if categories.Value == nil {
+		return fmt.Errorf("Error retrieving Diagnostics Categories for Resource %q: `categories.Value` was nil", actualResourceId)
+	}
+
+	d.SetId(actualResourceId)
+	val := *categories.Value
+
+	metrics := make([]string, 0)
+	logs := make([]string, 0)
+
+	for _, v := range val {
+		if v.Name == nil {
+			continue
+		}
+
+		if category := v.DiagnosticSettingsCategory; category != nil {
+			switch category.CategoryType {
+			case insights.Logs:
+				logs = append(logs, *v.Name)
+			case insights.Metrics:
+				metrics = append(metrics, *v.Name)
+			default:
+				return fmt.Errorf("Unsupported category type %q", string(category.CategoryType))
+			}
+		}
+	}
+
+	if err := d.Set("logs", logs); err != nil {
+		return fmt.Errorf("Error flattening `logs`: %+v", err)
+	}
+
+	if err := d.Set("metrics", metrics); err != nil {
+		return fmt.Errorf("Error flattening `metrics`: %+v", err)
+	}
+
+	return nil
+}

azurerm/data_source_monitor_diagnostic_categories_test.go

@@ -0,0 +1,105 @@
+package azurerm
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/hashicorp/terraform/helper/acctest"
+	"github.com/hashicorp/terraform/helper/resource"
+)
+
+func TestAccDataSourceArmMonitorDiagnosticCategories_appService(t *testing.T) {
+	dataSourceName := "data.azurerm_monitor_diagnostic_categories.test"
+	ri := acctest.RandInt()
+	location := testLocation()
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:  func() { testAccPreCheck(t) },
+		Providers: testAccProviders,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccDataSourceArmMonitorDiagnosticCategories_appService(ri, location),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr(dataSourceName, "metrics.#", "1"),
+					resource.TestCheckResourceAttr(dataSourceName, "logs.#", "1"),
+				),
+			},
+		},
+	})
+}
+
+func TestAccDataSourceArmMonitorDiagnosticCategories_storageAccount(t *testing.T) {
+	dataSourceName := "data.azurerm_monitor_diagnostic_categories.test"
+	rs := acctest.RandString(8)
+	location := testLocation()
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:  func() { testAccPreCheck(t) },
+		Providers: testAccProviders,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccDataSourceArmMonitorDiagnosticCategories_storageAccount(rs, location),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr(dataSourceName, "metrics.#", "2"),
+					resource.TestCheckResourceAttr(dataSourceName, "logs.#", "0"),
+				),
+			},
+		},
+	})
+}
+
+func testAccDataSourceArmMonitorDiagnosticCategories_appService(rInt int, location string) string {
+	return fmt.Sprintf(`
+resource "azurerm_resource_group" "test" {
+  name     = "acctestrg-%d"
+  location = "%s"
+}
+
+resource "azurerm_app_service_plan" "test" {
+  name                = "acctestASP-%d"
+  location            = "${azurerm_resource_group.test.location}"
+  resource_group_name = "${azurerm_resource_group.test.name}"
+
+  sku {
+    tier = "Standard"
+    size = "S1"
+  }
+}
+
+resource "azurerm_app_service" "test" {
+  name                = "acctestAS-%d"
+  location            = "${azurerm_resource_group.test.location}"
+  resource_group_name = "${azurerm_resource_group.test.name}"
+  app_service_plan_id = "${azurerm_app_service_plan.test.id}"
+}
+
+data "azurerm_monitor_diagnostic_categories" "test" {
+  resource_id = "${azurerm_app_service.test.id}"
+}
+`, rInt, location, rInt, rInt)
+}
+
+func testAccDataSourceArmMonitorDiagnosticCategories_storageAccount(rString, location string) string {
+	return fmt.Sprintf(`
+resource "azurerm_resource_group" "test" {
+  name     = "acctestrg-%s"
+  location = "%s"
+}
+
+resource "azurerm_storage_account" "test" {
+  name                     = "acctestsa%s"
+  resource_group_name      = "${azurerm_resource_group.test.name}"
+  location                 = "${azurerm_resource_group.test.location}"
+  account_tier             = "Standard"
+  account_replication_type = "GRS"
+
+  tags {
+    environment = "staging"
+  }
+}
+
+data "azurerm_monitor_diagnostic_categories" "test" {
+  resource_id = "${azurerm_storage_account.test.id}"
+}
+`, rString, location, rString)
+}

azurerm/provider.go

@@ -97,6 +97,7 @@ func Provider() terraform.ResourceProvider {
 			"azurerm_logic_app_workflow":                    dataSourceArmLogicAppWorkflow(),
 			"azurerm_managed_disk":                          dataSourceArmManagedDisk(),
 			"azurerm_management_group":                      dataSourceArmManagementGroup(),
+			"azurerm_monitor_diagnostic_categories":         dataSourceArmMonitorDiagnosticCategories(),
 			"azurerm_monitor_log_profile":                   dataSourceArmMonitorLogProfile(),
 			"azurerm_network_interface":                     dataSourceArmNetworkInterface(),
 			"azurerm_network_security_group":                dataSourceArmNetworkSecurityGroup(),

website/azurerm.erb

@@ -136,6 +136,10 @@
                     <a href="/docs/providers/azurerm/d/management_group.html">azurerm_management_group</a>
                 </li>
 
+                <li<%= sidebar_current("docs-azurerm-datasource-monitor-diagnostic-categories") %>>
+                    <a href="/docs/providers/azurerm/d/monitor_diagnostic_categories.html">azurerm_monitor_diagnostic_categories</a>
+                </li>
+
                 <li<%= sidebar_current("docs-azurerm-datasource-monitor-log-profile") %>>
                   <a href="/docs/providers/azurerm/d/monitor_log_profile.html">azurerm_monitor_log_profile</a>
                 </li>

website/docs/d/monitor_diagnostic_categories.html.markdown

@@ -0,0 +1,37 @@
+---
+layout: "azurerm"
+page_title: "Azure Resource Manager: azurerm_monitor_diagnostic_categories"
+sidebar_current: "docs-azurerm-datasource-monitor-diagnostic-categories"
+description: |-
+  Gets information about an the Monitor Diagnostics Categories supported by an existing Resource.
+
+---
+
+# Data Source: azurerm_monitor_diagnostic_categories
+
+Use this data source to access information about the Monitor Diagnostics Categories supported by an existing Resource.
+
+## Example Usage
+
+```hcl
+data "azurerm_dns_zone" "test" {
+  name                = "search-eventhubns"
+  resource_group_name = "search-service"
+}
+
+output "dns_zone_id" {
+  value = "${data.azurerm_dns_zone.test.id}"
+}
+```
+
+## Argument Reference
+
+* `resource_id` - (Required) The ID of an existing Resource which Monitor Diagnostics Categories should be retrieved for.
+
+## Attributes Reference
+
+* `id` - The ID of the Resource.
+
+* `logs` - A list of the Log Categories supported for this Resource.
+
+* `metrics` - A list of the Metric Categories supported for this Resource.