update expectedStatusCode only if over 0

0 means default (unspecified).

Author: fujiwara

mackerel/resource_mackerel_monitor.go

@@ -549,6 +549,7 @@ func expandMonitorExternalHTTP(d *schema.ResourceData) *mackerel.MonitorExternal
 		SkipCertificateVerification:     d.Get("external.0.skip_certificate_verification").(bool),
 		Headers:                         []mackerel.HeaderField{},
 		FollowRedirect:                  d.Get("external.0.follow_redirect").(bool),
+		ExpectedStatusCode:              nil,
 	}
 
 	if responseTimeCritical, ok := d.GetOkExists("external.0.response_time_critical"); ok {
@@ -573,7 +574,9 @@ func expandMonitorExternalHTTP(d *schema.ResourceData) *mackerel.MonitorExternal
 	}
 	if expectedStatusCode, ok := d.GetOkExists("external.0.expected_status_code"); ok {
 		expectedStatusCode := expectedStatusCode.(int)
-		monitor.ExpectedStatusCode = &expectedStatusCode
+		if expectedStatusCode > 0 {
+			monitor.ExpectedStatusCode = &expectedStatusCode
+		}
 	}
 	if headers, ok := d.GetOk("external.0.headers"); ok {
 		for name, value := range headers.(map[string]interface{}) {