provider/aws: Support of updates to ALB Listener Rule priority

Fixes: #9227

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSALBListenerRule_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/28 18:02:08 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSALBListenerRule_ -timeout 120m
=== RUN   TestAccAWSALBListenerRule_basic
--- PASS: TestAccAWSALBListenerRule_basic (261.41s)
=== RUN   TestAccAWSALBListenerRule_updateRulePriority
--- PASS: TestAccAWSALBListenerRule_updateRulePriority (289.84s)
=== RUN   TestAccAWSALBListenerRule_multipleConditionThrowsError
--- PASS: TestAccAWSALBListenerRule_multipleConditionThrowsError (0.01s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/aws	551.294s
```

builtin/providers/aws/resource_aws_alb_listener_rule.go

@@ -35,6 +35,7 @@ func resourceAwsAlbListenerRule() *schema.Resource {
 			"priority": {
 				Type:         schema.TypeInt,
 				Required:     true,
+				ForceNew:     true,
 				ValidateFunc: validateAwsAlbListenerRulePriority,
 			},
 			"action": {
@@ -184,10 +185,32 @@ func resourceAwsAlbListenerRuleRead(d *schema.ResourceData, meta interface{}) er
 func resourceAwsAlbListenerRuleUpdate(d *schema.ResourceData, meta interface{}) error {
 	elbconn := meta.(*AWSClient).elbv2conn
 
+	d.Partial(true)
+
+	if d.HasChange("priority") {
+		params := &elbv2.SetRulePrioritiesInput{
+			RulePriorities: []*elbv2.RulePriorityPair{
+				{
+					RuleArn:  aws.String(d.Id()),
+					Priority: aws.Int64(int64(d.Get("priority").(int))),
+				},
+			},
+		}
+
+		_, err := elbconn.SetRulePriorities(params)
+		if err != nil {
+			return err
+		}
+
+		d.SetPartial("priority")
+	}
+
+	requestUpdate := false
 	params := &elbv2.ModifyRuleInput{
 		RuleArn: aws.String(d.Id()),
 	}
 
+	if d.HasChange("action") {
 		actions := d.Get("action").([]interface{})
 		params.Actions = make([]*elbv2.Action, len(actions))
 		for i, action := range actions {
@@ -197,7 +220,11 @@ func resourceAwsAlbListenerRuleUpdate(d *schema.ResourceData, meta interface{})
 				Type:           aws.String(actionMap["type"].(string)),
 			}
 		}
+		requestUpdate = true
+		d.SetPartial("action")
+	}
 
+	if d.HasChange("condition") {
 		conditions := d.Get("condition").([]interface{})
 		params.Conditions = make([]*elbv2.RuleCondition, len(conditions))
 		for i, condition := range conditions {
@@ -211,7 +238,11 @@ func resourceAwsAlbListenerRuleUpdate(d *schema.ResourceData, meta interface{})
 				params.Conditions[i].Values[j] = aws.String(value.(string))
 			}
 		}
+		requestUpdate = true
+		d.SetPartial("condition")
+	}
 
+	if requestUpdate {
 		resp, err := elbconn.ModifyRule(params)
 		if err != nil {
 			return errwrap.Wrapf("Error modifying ALB Listener Rule: {{err}}", err)
@@ -220,6 +251,9 @@ func resourceAwsAlbListenerRuleUpdate(d *schema.ResourceData, meta interface{})
 		if len(resp.Rules) == 0 {
 			return errors.New("Error modifying creating ALB Listener Rule: no rules returned in response")
 		}
+	}
+
+	d.Partial(false)
 
 	return resourceAwsAlbListenerRuleRead(d, meta)
 }

builtin/providers/aws/resource_aws_alb_listener_rule_test.go

@@ -44,6 +44,35 @@ func TestAccAWSALBListenerRule_basic(t *testing.T) {
 	})
 }
 
+func TestAccAWSALBListenerRule_updateRulePriority(t *testing.T) {
+	var rule elbv2.Rule
+	albName := fmt.Sprintf("testrule-basic-%s", acctest.RandStringFromCharSet(13, acctest.CharSetAlphaNum))
+	targetGroupName := fmt.Sprintf("testtargetgroup-%s", acctest.RandStringFromCharSet(10, acctest.CharSetAlphaNum))
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:      func() { testAccPreCheck(t) },
+		IDRefreshName: "aws_alb_listener_rule.static",
+		Providers:     testAccProviders,
+		CheckDestroy:  testAccCheckAWSALBListenerRuleDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSALBListenerRuleConfig_basic(albName, targetGroupName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSALBListenerRuleExists("aws_alb_listener_rule.static", &rule),
+					resource.TestCheckResourceAttr("aws_alb_listener_rule.static", "priority", "100"),
+				),
+			},
+			{
+				Config: testAccAWSALBListenerRuleConfig_updateRulePriority(albName, targetGroupName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSALBListenerRuleExists("aws_alb_listener_rule.static", &rule),
+					resource.TestCheckResourceAttr("aws_alb_listener_rule.static", "priority", "101"),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSALBListenerRule_multipleConditionThrowsError(t *testing.T) {
 	albName := fmt.Sprintf("testrule-basic-%s", acctest.RandStringFromCharSet(13, acctest.CharSetAlphaNum))
 	targetGroupName := fmt.Sprintf("testtargetgroup-%s", acctest.RandStringFromCharSet(10, acctest.CharSetAlphaNum))
@@ -343,3 +372,115 @@ resource "aws_security_group" "alb_test" {
   }
 }`, albName, targetGroupName)
 }
+
+func testAccAWSALBListenerRuleConfig_updateRulePriority(albName, targetGroupName string) string {
+	return fmt.Sprintf(`
+resource "aws_alb_listener_rule" "static" {
+  listener_arn = "${aws_alb_listener.front_end.arn}"
+  priority = 101
+
+  action {
+    type = "forward"
+    target_group_arn = "${aws_alb_target_group.test.arn}"
+  }
+
+  condition {
+    field = "path-pattern"
+    values = ["/static/*"]
+  }
+}
+
+resource "aws_alb_listener" "front_end" {
+   load_balancer_arn = "${aws_alb.alb_test.id}"
+   protocol = "HTTP"
+   port = "80"
+
+   default_action {
+     target_group_arn = "${aws_alb_target_group.test.id}"
+     type = "forward"
+   }
+}
+
+resource "aws_alb" "alb_test" {
+  name            = "%s"
+  internal        = true
+  security_groups = ["${aws_security_group.alb_test.id}"]
+  subnets         = ["${aws_subnet.alb_test.*.id}"]
+
+  idle_timeout = 30
+  enable_deletion_protection = false
+
+  tags {
+    TestName = "TestAccAWSALB_basic"
+  }
+}
+
+resource "aws_alb_target_group" "test" {
+  name = "%s"
+  port = 8080
+  protocol = "HTTP"
+  vpc_id = "${aws_vpc.alb_test.id}"
+
+  health_check {
+    path = "/health"
+    interval = 60
+    port = 8081
+    protocol = "HTTP"
+    timeout = 3
+    healthy_threshold = 3
+    unhealthy_threshold = 3
+    matcher = "200-299"
+  }
+}
+
+variable "subnets" {
+  default = ["10.0.1.0/24", "10.0.2.0/24"]
+  type    = "list"
+}
+
+data "aws_availability_zones" "available" {}
+
+resource "aws_vpc" "alb_test" {
+  cidr_block = "10.0.0.0/16"
+
+  tags {
+    TestName = "TestAccAWSALB_basic"
+  }
+}
+
+resource "aws_subnet" "alb_test" {
+  count                   = 2
+  vpc_id                  = "${aws_vpc.alb_test.id}"
+  cidr_block              = "${element(var.subnets, count.index)}"
+  map_public_ip_on_launch = true
+  availability_zone       = "${element(data.aws_availability_zones.available.names, count.index)}"
+
+  tags {
+    TestName = "TestAccAWSALB_basic"
+  }
+}
+
+resource "aws_security_group" "alb_test" {
+  name        = "allow_all_alb_test"
+  description = "Used for ALB Testing"
+  vpc_id      = "${aws_vpc.alb_test.id}"
+
+  ingress {
+    from_port   = 0
+    to_port     = 0
+    protocol    = "-1"
+    cidr_blocks = ["0.0.0.0/0"]
+  }
+
+  egress {
+    from_port   = 0
+    to_port     = 0
+    protocol    = "-1"
+    cidr_blocks = ["0.0.0.0/0"]
+  }
+
+  tags {
+    TestName = "TestAccAWSALB_basic"
+  }
+}`, albName, targetGroupName)
+}