Domain sni_endpoint_id cooperation with ACM (#361)

* Domain sni_endpoint_id should not be computed, so that it remains unset for ACM apps

* Domain should not read/set sni_endpoint_id for ACM apps

* Update Domain docs with ACM vs manual cert management differences

docs/resources/domain.md

@@ -23,25 +23,29 @@ resource "heroku_app" "default" {
 # Associate a custom domain
 resource "heroku_domain" "default" {
   app_id   = heroku_app.default.id
-  hostname = "terraform.example.com"
+  hostname = "www.example.com"
 }
 ```
 
 ## Argument Reference
 
-The following arguments are supported:
-
-* `hostname` - (Required) The hostname to serve requests from.
 * `app_id` - (Required) Heroku app ID (do not use app name)
 
+For apps with ACM enabled (automated certificate management):
+
+* `hostname` - (Required) The hostname to setup via ACM.
+
+For apps with `heroku_ssl` (SNI Endpoint) resources (manual certificate management):
+
+* `hostname` - (Required) Must match common name or a subject alternative name of certificate in the `heroku_ssl` resource references by `sni_endpoint_id`.
+* `sni_endpoint_id` - (Required) The ID of the `heroku_ssl` resource to associate the domain with.
+
 ## Attributes Reference
 
 The following attributes are exported:
 
 * `id` - The ID of the domain record.
-* `hostname` - The hostname traffic will be served as.
 * `cname` - The CNAME traffic should route to.
-* `sni_endpoint_id` - The ID of the heroku_ssl resource to associate the domain with.
 
 ## Importing
 

heroku/resource_heroku_domain.go

@@ -43,7 +43,6 @@ func resourceHerokuDomain() *schema.Resource {
 
 			"sni_endpoint_id": {
 				Type:     schema.TypeString,
-				Computed: true,
 				Optional: true,
 			},
 		},
@@ -72,7 +71,10 @@ func resourceHerokuDomainImport(d *schema.ResourceData, meta interface{}) ([]*sc
 		return nil, err
 	}
 
-	populateResource(d, do)
+	err = populateResource(d, do, client)
+	if err != nil {
+		return nil, fmt.Errorf("Error populating domain attributes: %w", err)
+	}
 
 	return []*schema.ResourceData{d}, nil
 }
@@ -94,7 +96,10 @@ func resourceHerokuDomainCreate(d *schema.ResourceData, meta interface{}) error
 	if err != nil {
 		return err
 	}
-	populateResource(d, do)
+	err = populateResource(d, do, client)
+	if err != nil {
+		return fmt.Errorf("Error populating domain attributes: %w", err)
+	}
 
 	config := meta.(*Config)
 	time.Sleep(time.Duration(config.PostDomainCreateDelay) * time.Second)
@@ -117,7 +122,10 @@ func resourceHerokuDomainUpdate(d *schema.ResourceData, meta interface{}) error
 		return err
 	}
 
-	populateResource(d, do)
+	err = populateResource(d, do, client)
+	if err != nil {
+		return fmt.Errorf("Error populating domain attributes: %w", err)
+	}
 
 	return nil
 }
@@ -146,19 +154,28 @@ func resourceHerokuDomainRead(d *schema.ResourceData, meta interface{}) error {
 	}
 
 	log.Printf("[INFO] Reading Domain: %s", d.Id())
-	populateResource(d, do)
+	err = populateResource(d, do, client)
+	if err != nil {
+		return fmt.Errorf("Error populating domain attributes: %w", err)
+	}
 
 	return nil
 }
 
-func populateResource(d *schema.ResourceData, do *heroku.Domain) {
+func populateResource(d *schema.ResourceData, do *heroku.Domain, client *heroku.Service) error {
 	d.SetId(do.ID)
 	d.Set("app_id", do.App.ID)
 	d.Set("hostname", do.Hostname)
 	d.Set("cname", do.CName)
-	if v := do.SniEndpoint; v != nil {
+	// Do not capture SNI Endpoint when ACM is active
+	hasACM, err := retrieveAcm(do.App.ID, client)
+	if err != nil {
+		return err
+	}
+	if v := do.SniEndpoint; !hasACM && v != nil {
 		d.Set("sni_endpoint_id", v.ID)
 	}
+	return nil
 }
 
 func resourceHerokuDomainV0() *schema.Resource {

heroku/resource_heroku_domain_test.go

@@ -38,6 +38,31 @@ func TestAccHerokuDomain_Basic(t *testing.T) {
 	})
 }
 
+func TestAccHerokuDomain_ACM(t *testing.T) {
+	var domain heroku.Domain
+	var endpoint heroku.SniEndpoint
+	randString := acctest.RandString(10)
+	appName := fmt.Sprintf("tftest-%s", randString)
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckHerokuDomainDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccCheckHerokuDomainConfig_ACM(appName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckHerokuDomainExists("heroku_domain.one", &domain),
+					testAccCheckHerokuDomainAttributes(&domain, &endpoint),
+					resource.TestCheckResourceAttr("heroku_domain.one", "hostname", "terraform-tftest-"+randString+".example.com"),
+					resource.TestCheckResourceAttrSet("heroku_domain.one", "app_id"),
+					resource.TestCheckNoResourceAttr("heroku_domain.one", "sni_endpoint_id"),
+				),
+			},
+		},
+	})
+}
+
 func TestAccHerokuDomain_No_SSL_Change(t *testing.T) {
 	var domain heroku.Domain
 	var endpoint heroku.SniEndpoint
@@ -338,3 +363,16 @@ resource "heroku_domain" "one" {
   hostname = "terraform-%s.example.com"
 }`, appName, appName)
 }
+
+func testAccCheckHerokuDomainConfig_ACM(appName string) string {
+	return fmt.Sprintf(`resource "heroku_app" "one" {
+    name = "%s"
+    region = "us"
+    acm = true
+}
+
+resource "heroku_domain" "one" {
+  app_id = heroku_app.one.id
+  hostname = "terraform-%s.example.com"
+}`, appName, appName)
+}