resource/autoscaling_group: reintroduce changes made in #9478

aws/resource_aws_autoscaling_attachment_test.go

@@ -250,6 +250,10 @@ resource "aws_autoscaling_group" "asg" {
     value               = "terraform-asg-lg-assoc-test"
     propagate_at_launch = true
   }
+
+  lifecycle {
+    ignore_changes = [load_balancers, target_group_arns]
+  }
 }
 
 resource "aws_launch_configuration" "as_conf" {
@@ -313,6 +317,10 @@ resource "aws_autoscaling_group" "asg" {
     value               = "terraform-asg-lg-assoc-test"
     propagate_at_launch = true
   }
+
+  lifecycle {
+    ignore_changes = [load_balancers, target_group_arns]
+  }
 }
 `, rInt, rInt)
 }

aws/resource_aws_autoscaling_group.go

@@ -262,12 +262,9 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				Optional: true,
 			},
 
-			// DEPRECATED: Computed: true should be removed in a major version release
-			// Reference: https://github.com/terraform-providers/terraform-provider-aws/issues/9513
 			"load_balancers": {
 				Type:     schema.TypeSet,
 				Optional: true,
-				Computed: true,
 				Elem:     &schema.Schema{Type: schema.TypeString},
 				Set:      schema.HashString,
 			},
@@ -337,12 +334,9 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				Default:  false,
 			},
 
-			// DEPRECATED: Computed: true should be removed in a major version release
-			// Reference: https://github.com/terraform-providers/terraform-provider-aws/issues/9513
 			"target_group_arns": {
 				Type:     schema.TypeSet,
 				Optional: true,
-				Computed: true,
 				Elem:     &schema.Schema{Type: schema.TypeString},
 				Set:      schema.HashString,
 			},

aws/resource_aws_autoscaling_group_test.go

@@ -461,6 +461,7 @@ func TestAccAWSAutoScalingGroup_WithLoadBalancer(t *testing.T) {
 
 func TestAccAWSAutoScalingGroup_WithLoadBalancer_ToTargetGroup(t *testing.T) {
 	var group autoscaling.Group
+	resourceName := "aws_autoscaling_group.bar"
 
 	resource.ParallelTest(t, resource.TestCase{
 		PreCheck:     func() { testAccPreCheck(t) },
@@ -470,13 +471,13 @@ func TestAccAWSAutoScalingGroup_WithLoadBalancer_ToTargetGroup(t *testing.T) {
 			{
 				Config: testAccAWSAutoScalingGroupConfigWithLoadBalancer,
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutoScalingGroupExists("aws_autoscaling_group.bar", &group),
-					resource.TestCheckResourceAttr("aws_autoscaling_group.bar", "load_balancers.#", "1"),
-					resource.TestCheckResourceAttr("aws_autoscaling_group.bar", "target_group_arns.#", "0"),
+					testAccCheckAWSAutoScalingGroupExists(resourceName, &group),
+					resource.TestCheckResourceAttr(resourceName, "load_balancers.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "target_group_arns.#", "0"),
 				),
 			},
 			{
-				ResourceName:      "aws_autoscaling_group.bar",
+				ResourceName:      resourceName,
 				ImportState:       true,
 				ImportStateVerify: true,
 				ImportStateVerifyIgnore: []string{
@@ -492,14 +493,13 @@ func TestAccAWSAutoScalingGroup_WithLoadBalancer_ToTargetGroup(t *testing.T) {
 			{
 				Config: testAccAWSAutoScalingGroupConfigWithTargetGroup,
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutoScalingGroupExists("aws_autoscaling_group.bar", &group),
-					resource.TestCheckResourceAttr("aws_autoscaling_group.bar", "target_group_arns.#", "1"),
-					// DEPRECATED: This value will be 0 when Computed: true is removed
-					resource.TestCheckResourceAttr("aws_autoscaling_group.bar", "load_balancers.#", "1"),
+					testAccCheckAWSAutoScalingGroupExists(resourceName, &group),
+					resource.TestCheckResourceAttr(resourceName, "target_group_arns.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "load_balancers.#", "0"),
 				),
 			},
 			{
-				ResourceName:      "aws_autoscaling_group.bar",
+				ResourceName:      resourceName,
 				ImportState:       true,
 				ImportStateVerify: true,
 				ImportStateVerifyIgnore: []string{
@@ -515,14 +515,13 @@ func TestAccAWSAutoScalingGroup_WithLoadBalancer_ToTargetGroup(t *testing.T) {
 			{
 				Config: testAccAWSAutoScalingGroupConfigWithLoadBalancer,
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutoScalingGroupExists("aws_autoscaling_group.bar", &group),
-					resource.TestCheckResourceAttr("aws_autoscaling_group.bar", "load_balancers.#", "1"),
-					// DEPRECATED: This value will be 0 when Computed: true is removed
-					resource.TestCheckResourceAttr("aws_autoscaling_group.bar", "target_group_arns.#", "1"),
+					testAccCheckAWSAutoScalingGroupExists(resourceName, &group),
+					resource.TestCheckResourceAttr(resourceName, "load_balancers.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "target_group_arns.#", "0"),
 				),
 			},
 			{
-				ResourceName:      "aws_autoscaling_group.bar",
+				ResourceName:      resourceName,
 				ImportState:       true,
 				ImportStateVerify: true,
 				ImportStateVerifyIgnore: []string{

website/docs/guides/version-3-upgrade.html.md

@@ -160,6 +160,61 @@ output "lambda_result" {
 
 Specifying both the `availability_zones` and `vpc_zone_identifier` arguments previously led to confusing behavior and errors. Now this issue is reported at plan-time. Use the `null` value instead of `[]` (empty list) in conditionals to ensure this validation does not unexpectedly trigger.
 
+### Drift detection enabled for `load_balancers` and `target_group_arns` arguments
+
+If you previously set one of these arguments to an empty list to enable drift detection (e.g. when migrating an ASG from ELB to ALB), this can be updated as follows.
+
+For example, given this previous configuration:
+
+```hcl
+resource "aws_autoscaling_group" "example" {
+  # ... other configuration ...
+  load_balancers = []
+  target_group_arns = [aws_lb_target_group.example.arn]
+}
+```
+
+An updated configuration:
+
+```hcl
+resource "aws_autoscaling_group" "example" {
+  # ... other configuration ...
+  target_group_arns = [aws_lb_target_group.example.arn]
+}
+```
+
+If `aws_autoscaling_attachment` resources reference your ASG configurations, you will need to add the [`lifecycle` configuration block](/docs/configuration/resources.html#lifecycle-lifecycle-customizations) with an `ignore_changes` argument to prevent Terraform non-empty plans (i.e. forcing resource update) during the next state refresh.
+
+For example, given this previous configuration:
+
+```hcl
+resource "aws_autoscaling_attachment" "example" {
+  autoscaling_group_name = aws_autoscaling_group.example.id
+  elb                    = aws_elb.example.id
+}
+
+resource "aws_autoscaling_group" "example"{
+  # ... other configuration ...
+}
+```
+
+An updated configuration:
+
+```hcl
+resource "aws_autoscaling_attachment" "example" {
+  autoscaling_group_name = aws_autoscaling_group.example.id
+  elb                    = aws_elb.example.id
+}
+
+resource "aws_autoscaling_group" "example"{
+  # ... other configuration ...
+
+  lifecycle {
+    ignore_changes = [load_balancers, target_group_arns]
+  }
+}
+```
+
 ## Resource: aws_dx_gateway
 
 ### Removal of Automatic aws_dx_gateway_association Import

website/docs/r/autoscaling_attachment.html.markdown

@@ -12,26 +12,44 @@ Provides an AutoScaling Attachment resource.
 
 ~> **NOTE on AutoScaling Groups and ASG Attachments:** Terraform currently provides
 both a standalone ASG Attachment resource (describing an ASG attached to
-an ELB), and an [AutoScaling Group resource](autoscaling_group.html) with
-`load_balancers` defined in-line. At this time you cannot use an ASG with in-line
-load balancers in conjunction with an ASG Attachment resource. Doing so will cause a
-conflict and will overwrite attachments.
+an ELB or ALB), and an [AutoScaling Group resource](autoscaling_group.html) with
+`load_balancers` and `target_group_arns` defined in-line. At this time you can use an ASG with in-line
+`load balancers` or `target_group_arns` in conjunction with an ASG Attachment resource, however, to prevent
+unintended resource updates, the `aws_autoscaling_group` resource must be configured 
+to ignore changes to the `load_balancers` and `target_group_arns` arguments within a [`lifecycle` configuration block](/docs/configuration/resources.html#lifecycle-lifecycle-customizations).
 
 ## Example Usage
 
 ```hcl
 # Create a new load balancer attachment
 resource "aws_autoscaling_attachment" "asg_attachment_bar" {
-  autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
-  elb                    = "${aws_elb.bar.id}"
+  autoscaling_group_name = aws_autoscaling_group.asg.id
+  elb                    = aws_elb.bar.id
 }
 ```
 
 ```hcl
 # Create a new ALB Target Group attachment
 resource "aws_autoscaling_attachment" "asg_attachment_bar" {
-  autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
-  alb_target_group_arn   = "${aws_alb_target_group.test.arn}"
+  autoscaling_group_name = aws_autoscaling_group.asg.id
+  alb_target_group_arn   = aws_alb_target_group.test.arn
+}
+```
+
+## With An AutoScaling Group Resource
+
+```hcl
+resource "aws_autoscaling_group" "asg" {
+  # ... other configuration ...
+
+  lifecycle {
+    ignore_changes = [load_balancers, target_group_arns]
+  }
+}
+
+resource "aws_autoscaling_attachment" "asg_attachment_bar" {
+  autoscaling_group_name = aws_autoscaling_group.asg.id
+  elb                    = aws_elb.test.id
 }
 ```
 

website/docs/r/autoscaling_group.html.markdown

@@ -304,10 +304,6 @@ In addition to all arguments above, the following attributes are exported:
 * `desired_capacity` -The number of Amazon EC2 instances that should be running in the group.
 * `launch_configuration` - The launch configuration of the autoscale group
 * `vpc_zone_identifier` (Optional) - The VPC zone identifier
-* `load_balancers` (Optional) The load balancer names associated with the
-   autoscaling group.
-* `target_group_arns` (Optional) list of Target Group ARNs that apply to this
-AutoScaling Group
 
 ~> **NOTE:** When using `ELB` as the `health_check_type`, `health_check_grace_period` is required.