Fix circonus)_rule_sets for optional links. (#12614)

* Add a `validateHTTPURL` flag to allow URLs in `circonus_rule_set`s to be optional.

* Fix reading `circonus_rule_set` `criteria`.

builtin/providers/circonus/resource_circonus_rule_set.go

@@ -270,7 +270,7 @@ func resourceRuleSet() *schema.Resource {
 				Type:         schema.TypeString,
 				Optional:     true,
 				Computed:     true,
-				ValidateFunc: validateHTTPURL(ruleSetLinkAttr, urlIsAbs),
+				ValidateFunc: validateHTTPURL(ruleSetLinkAttr, urlIsAbs|urlOptional),
 			},
 			ruleSetMetricTypeAttr: &schema.Schema{
 				Type:         schema.TypeString,
@@ -369,9 +369,9 @@ func ruleSetRead(d *schema.ResourceData, meta interface{}) error {
 		case apiRuleSetMinValue:
 			valueAttrs[string(ruleSetMinValueAttr)] = rule.Value
 		case apiRuleSetNotContains:
-			valueAttrs[string(ruleSetNotMatchAttr)] = rule.Value
-		case apiRuleSetNotMatch:
 			valueAttrs[string(ruleSetNotContainAttr)] = rule.Value
+		case apiRuleSetNotMatch:
+			valueAttrs[string(ruleSetNotMatchAttr)] = rule.Value
 		default:
 			return fmt.Errorf("PROVIDER BUG: Unsupported criteria %q", rule.Criteria)
 		}

builtin/providers/circonus/validators.go

@@ -313,14 +313,20 @@ type urlParseFlags int
 
 const (
 	urlIsAbs urlParseFlags = 1 << iota
-	urlWithoutSchema
+	urlOptional
 	urlWithoutPort
+	urlWithoutSchema
 )
 
 const urlBasicCheck urlParseFlags = 0
 
 func validateHTTPURL(attrName schemaAttr, checkFlags urlParseFlags) func(v interface{}, key string) (warnings []string, errors []error) {
 	return func(v interface{}, key string) (warnings []string, errors []error) {
+		s := v.(string)
+		if checkFlags&urlOptional != 0 && s == "" {
+			return warnings, errors
+		}
+
 		u, err := url.Parse(v.(string))
 		switch {
 		case err != nil: