plugin/header: Remove deprecated syntax (#7436)

Signed-off-by: Qasim Sarfraz <qasimsarfraz@microsoft.com>

plugin/header/README.md

@@ -13,12 +13,12 @@ The modifications are made transparently for the client and subsequent plugins.
 
 ~~~
 header {
-    [SELECTOR] ACTION FLAGS...
-    [SELECTOR] ACTION FLAGS...
+    SELECTOR ACTION FLAGS...
+    SELECTOR ACTION FLAGS...
 }
 ~~~
 
-* **SELECTOR** defines if the action should be applied on `query` or `response`. In future CoreDNS version the selector will be mandatory. For backwards compatibility the action will be applied on `response` if the selector is undefined.
+* **SELECTOR** defines if the action should be applied on `query` or `response`.
 
 * **ACTION** defines the state for DNS message header flags. Actions are evaluated in the order they are defined so last one has the
   most precedence. Allowed values are:

plugin/header/setup.go

@@ -38,14 +38,6 @@ func parse(c *caddy.Controller) ([]Rule, []Rule, error) {
 
 			var action string
 			switch selector {
-			case "set", "clear":
-				log.Warningf("The selector for header rule in line %d isn't explicit defined. "+
-					"Assume rule applies for selector 'response'. This syntax is deprecated. "+
-					"In future versions of CoreDNS the selector must be explicit defined.",
-					c.Line())
-
-				action = selector
-				selector = "response"
 			case "query", "response":
 				if c.NextArg() {
 					action = c.Val()

plugin/header/setup_test.go

@@ -14,24 +14,18 @@ func TestSetupHeader(t *testing.T) {
 		expectedErrContent string
 	}{
 		{`header {}`, true, "Wrong argument count or unexpected line ending after"},
-		{`header {
-					set
-}`, true, "invalid length for flags, at least one should be provided"},
 		{`header {
 					foo
 }`, true, "invalid selector=foo should be query or response"},
+		{`header {
+					response set
+}`, true, "invalid length for flags, at least one should be provided"},
 		{`header {
 					query foo
 }`, true, "invalid length for flags, at least one should be provided"},
 		{`header {
 					query foo rd
 }`, true, "unknown flag action=foo, should be set or clear"},
-		{`header {
-					set ra
-}`, false, ""},
-		{`header {
-					clear ra
-		}`, false, ""},
 		{`header {
 					query set rd
 		}`, false, ""},
@@ -39,8 +33,8 @@ func TestSetupHeader(t *testing.T) {
 					response set aa
 		}`, false, ""},
 		{`header {
-			set ra aa
-			clear rd
+			response set ra aa
+			query clear rd
 }`, false, ""},
 	}