provider/aws: Fix issue updating Elastic Beanstalk Environment variables (#8848)

* provider/aws: failing test case for updating env vars

* provider/aws: Fix issue with updating Elastic Beanstalk env vars

builtin/providers/aws/resource_aws_elastic_beanstalk_environment.go

@@ -337,11 +337,10 @@ func resourceAwsElasticBeanstalkEnvironmentUpdate(d *schema.ResourceData, meta i
 		// Because of this, we need to remove any settings in the "removable"
 		// settings that are also found in the "add" settings, otherwise they
 		// conflict. Here we loop through all the initial removables from the set
-		// difference, and we build up a slice of settings not found in the "add"
-		// set
-		var remove []*elasticbeanstalk.ConfigurationOptionSetting
+		// difference, and delete from the slice any items found in both `add` and
+		// `rm` above
 		if len(add) > 0 {
-			for _, r := range rm {
+			for i, r := range rm {
 				for _, a := range add {
 					// ResourceNames are optional. Some defaults come with it, some do
 					// not. We need to guard against nil/empty in state as well as
@@ -355,16 +354,14 @@ func resourceAwsElasticBeanstalkEnvironmentUpdate(d *schema.ResourceData, meta i
 						}
 					}
 					if *r.Namespace == *a.Namespace && *r.OptionName == *a.OptionName {
-						continue
+						log.Printf("[DEBUG] Removing Beanstalk setting: (%s::%s)", *a.Namespace, *a.OptionName)
+						rm = append(rm[:i], rm[i+1:]...)
 					}
-					remove = append(remove, r)
 				}
 			}
-		} else {
-			remove = rm
 		}
 
-		for _, elem := range remove {
+		for _, elem := range rm {
 			updateOpts.OptionsToRemove = append(updateOpts.OptionsToRemove, &elasticbeanstalk.OptionSpecification{
 				Namespace:  elem.Namespace,
 				OptionName: elem.OptionName,

builtin/providers/aws/resource_aws_elastic_beanstalk_environment_test.go

@@ -238,6 +238,13 @@ func TestAccAWSBeanstalkEnv_basic_settings_update(t *testing.T) {
 					testAccVerifyBeanstalkConfig(&app, []string{"TF_LOG", "TF_SOME_VAR"}),
 				),
 			},
+			resource.TestStep{
+				Config: testAccBeanstalkEnvConfig_settings_update(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckBeanstalkEnvExists("aws_elastic_beanstalk_environment.tfenvtest", &app),
+					testAccVerifyBeanstalkConfig(&app, []string{"TF_LOG", "TF_SOME_VAR"}),
+				),
+			},
 			resource.TestStep{
 				Config: testAccBeanstalkEnvConfig_empty_settings(rInt),
 				Check: resource.ComposeTestCheckFunc(
@@ -530,6 +537,61 @@ resource "aws_elastic_beanstalk_environment" "tfenvtest" {
 }`, r, r)
 }
 
+func testAccBeanstalkEnvConfig_settings_update(r int) string {
+	return fmt.Sprintf(`
+resource "aws_elastic_beanstalk_application" "tftest" {
+  name = "tf-test-name-%d"
+  description = "tf-test-desc"
+}
+
+resource "aws_elastic_beanstalk_environment" "tfenvtest" {
+  name                = "tf-test-name-%d"
+  application         = "${aws_elastic_beanstalk_application.tftest.name}"
+  solution_stack_name = "64bit Amazon Linux running Python"
+
+        wait_for_ready_timeout = "15m"
+
+  setting {
+    namespace = "aws:elasticbeanstalk:application:environment"
+    name      = "TF_LOG"
+    value     = "true"
+  }
+
+  setting {
+    namespace = "aws:elasticbeanstalk:application:environment"
+    name      = "TF_SOME_VAR"
+    value     = "false"
+  }
+
+	  setting {
+    namespace = "aws:elasticbeanstalk:application:environment"
+    name      = "TF_SOME_NEW_VAR"
+    value     = "true"
+  }
+
+  setting {
+    namespace = "aws:autoscaling:scheduledaction"
+    resource  = "ScheduledAction01"
+    name      = "MinSize"
+    value     = 2
+  }
+
+  setting {
+    namespace = "aws:autoscaling:scheduledaction"
+    resource  = "ScheduledAction01"
+    name      = "MaxSize"
+    value     = 3
+  }
+
+  setting {
+    namespace = "aws:autoscaling:scheduledaction"
+    resource  = "ScheduledAction01"
+    name      = "StartTime"
+    value     = "2016-07-28T04:07:02Z"
+  }
+}`, r, r)
+}
+
 const testAccBeanstalkWorkerEnvConfig = `
 resource "aws_iam_instance_profile" "tftest" {
   name = "tftest_profile"