From 00dfc4d086ab846c0ecb3cf723b2742404468711 Mon Sep 17 00:00:00 2001
From: Tom Bamford <tom@bamford.io>
Date: Tue, 16 Jun 2020 04:47:33 +0100
Subject: [PATCH] azuread_group: new property `prevent_duplicate_names`

---
 azuread/helpers/graph/group.go | 28 ++++++++++++++++++++++++++++
 azuread/resource_group.go      | 16 ++++++++++++++++
 azuread/resource_group_test.go | 28 ++++++++++++++++++++++++++++
 website/docs/r/group.markdown  |  1 +
 4 files changed, 73 insertions(+)

diff --git a/azuread/helpers/graph/group.go b/azuread/helpers/graph/group.go
index 325eb19d86..5ee3c98540 100644
--- a/azuread/helpers/graph/group.go
+++ b/azuread/helpers/graph/group.go
@@ -182,3 +182,31 @@ func GroupAddOwners(client graphrbac.GroupsClient, ctx context.Context, groupId
 
 	return nil
 }
+
+func GroupFindByName(client graphrbac.GroupsClient, ctx context.Context, name string) (*graphrbac.ADGroup, error) {
+	nameFilter := fmt.Sprintf("displayName eq '%s'", name)
+	resp, err := client.List(ctx, nameFilter)
+
+	if err != nil {
+		return nil, fmt.Errorf("unable to list Groups with filter %q: %+v", nameFilter, err)
+	}
+
+	for _, group := range resp.Values() {
+		if *group.DisplayName == name {
+			return &group, nil
+		}
+	}
+
+	return nil, nil
+}
+
+func GroupCheckNameAvailability(client graphrbac.GroupsClient, ctx context.Context, name string) error {
+	existingGroup, err := GroupFindByName(client, ctx, name)
+	if err != nil {
+		return err
+	}
+	if existingGroup != nil {
+		return fmt.Errorf("existing Azure Active Directory Group with name %q (ObjID: %q) was found and `prevent_duplicate_names` was specified", name, *existingGroup.ObjectID)
+	}
+	return nil
+}
diff --git a/azuread/resource_group.go b/azuread/resource_group.go
index 17565aac48..f08620e6c9 100644
--- a/azuread/resource_group.go
+++ b/azuread/resource_group.go
@@ -68,6 +68,11 @@ func resourceGroup() *schema.Resource {
 				Type:     schema.TypeString,
 				Computed: true,
 			},
+			"prevent_duplicate_names": {
+				Type:     schema.TypeBool,
+				Optional: true,
+				Default:  false,
+			},
 		},
 	}
 }
@@ -78,6 +83,13 @@ func resourceGroupCreate(d *schema.ResourceData, meta interface{}) error {
 
 	name := d.Get("name").(string)
 
+	if d.Get("prevent_duplicate_names").(bool) {
+		err := graph.GroupCheckNameAvailability(client, ctx, name)
+		if err != nil {
+			return err
+		}
+	}
+
 	properties := graphrbac.GroupCreateParameters{
 		DisplayName:          &name,
 		MailEnabled:          p.Bool(false),                 // we're defaulting to false, as the API currently only supports the creation of non-mail enabled security groups.
@@ -168,6 +180,10 @@ func resourceGroupRead(d *schema.ResourceData, meta interface{}) error {
 	}
 	d.Set("owners", owners)
 
+	if preventDuplicates := d.Get("prevent_duplicate_names").(bool); !preventDuplicates {
+		d.Set("prevent_duplicate_names", false)
+	}
+
 	return nil
 }
 
diff --git a/azuread/resource_group_test.go b/azuread/resource_group_test.go
index 83cb8f58b0..95148abe6d 100644
--- a/azuread/resource_group_test.go
+++ b/azuread/resource_group_test.go
@@ -2,6 +2,7 @@ package azuread
 
 import (
 	"fmt"
+	"regexp"
 	"testing"
 
 	"github.com/hashicorp/terraform-plugin-sdk/helper/acctest"
@@ -286,6 +287,22 @@ func TestAccAzureADGroup_ownersUpdate(t *testing.T) {
 	})
 }
 
+func TestAccAzureADGroup_preventDuplicateNames(t *testing.T) {
+	ri := tf.AccRandTimeInt()
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testCheckADApplicationDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config:      testAccAzureADGroup_duplicateName(ri),
+				ExpectError: regexp.MustCompile("existing Azure Active Directory Group .+ was found"),
+			},
+		},
+	})
+}
+
 func testCheckAzureADGroupExists(name string) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		rs, ok := s.RootModule().Resources[name]
@@ -503,3 +520,14 @@ resource "azuread_group" "test" {
 }
 `, id)
 }
+
+func testAccAzureADGroup_duplicateName(id int) string {
+	return fmt.Sprintf(`
+%s
+
+resource "azuread_group" "duplicate" {
+  name                    = azuread_group.test.name
+  prevent_duplicate_names = true
+}
+`, testAccAzureADGroup_basic(id))
+}
diff --git a/website/docs/r/group.markdown b/website/docs/r/group.markdown
index 5dee3c0a9d..97aa609a43 100644
--- a/website/docs/r/group.markdown
+++ b/website/docs/r/group.markdown
@@ -49,6 +49,7 @@ The following arguments are supported:
 * `description` - (Optional) The description for the Group.  Changing this forces a new resource to be created.
 * `members` (Optional) A set of members who should be present in this Group. Supported Object types are Users, Groups or Service Principals.
 * `owners` (Optional) A set of owners who own this Group. Supported Object types are Users or Service Principals.
+* `prevent_duplicate_names` - (Optional) If `true`, will return an error when an existing Application is found with the same name. Defaults to `false`.
 
 -> **NOTE:** Group names are not unique within Azure Active Directory.