Make RRdatas case insensitive.

The GCP backend apparently lowercases the values, no matter what you
enter, so we consider uppercase and lowercase values to be equivalent.
This fixes #862.

google/resource_dns_record_set.go

@@ -40,7 +40,7 @@ func resourceDnsRecordSet() *schema.Resource {
 					Type: schema.TypeString,
 				},
 				DiffSuppressFunc: func(k, old, new string, d *schema.ResourceData) bool {
-					return strings.Trim(old, `"`) == strings.Trim(new, `"`)
+					return strings.ToLower(strings.Trim(old, `"`)) == strings.ToLower(strings.Trim(new, `"`))
 				},
 			},
 

google/resource_dns_record_set_test.go

@@ -162,6 +162,26 @@ func TestAccDnsRecordSet_quotedTXT(t *testing.T) {
 	})
 }
 
+func TestAccDnsRecordSet_uppercaseMX(t *testing.T) {
+	t.Parallel()
+
+	zoneName := fmt.Sprintf("dnszone-test-txt-%s", acctest.RandString(10))
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckDnsRecordSetDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: testAccDnsRecordSet_uppercaseMX(zoneName, 300),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckDnsRecordSetExists(
+						"google_dns_record_set.foobar", zoneName),
+				),
+			},
+		},
+	})
+}
+
 func testAccCheckDnsRecordSetDestroy(s *terraform.State) error {
 	config := testAccProvider.Meta().(*Config)
 
@@ -296,3 +316,26 @@ func testAccDnsRecordSet_quotedTXT(name string, ttl int) string {
 	}
 	`, name, name, name, ttl)
 }
+
+func testAccDnsRecordSet_uppercaseMX(name string, ttl int) string {
+	return fmt.Sprintf(`
+	resource "google_dns_managed_zone" "parent-zone" {
+		name = "%s"
+		dns_name = "%s.hashicorptest.com."
+		description = "Test Description"
+	}
+	resource "google_dns_record_set" "foobar" {
+		managed_zone = "${google_dns_managed_zone.parent-zone.name}"
+		name = "test-record.%s.hashicorptest.com."
+		type = "MX"
+		rrdatas = [
+			"1 ASPMX.L.GOOGLE.COM.",
+			"5 ALT1.ASPMX.L.GOOGLE.COM.",
+			"5 ALT2.ASPMX.L.GOOGLE.COM.",
+			"10 ASPMX2.GOOGLEMAIL.COM.",
+			"10 ASPMX3.GOOGLEMAIL.COM.",
+		]
+		ttl = %d
+	}
+	`, name, name, name, ttl)
+}