validate: warn on deprecated keys

config/validate/rules.go

@@ -82,6 +82,9 @@ func checkNodeStructure(n, g node, r *Report) {
 	case reflect.Struct:
 		for _, cn := range n.children {
 			if cg := g.Child(cn.name); cg.IsValid() {
+				if msg := cg.field.Tag.Get("deprecated"); msg != "" {
+					r.Warning(cn.line, fmt.Sprintf("deprecated key %q (%s)", cn.name, msg))
+				}
 				checkNodeStructure(cn, cg, r)
 			} else {
 				r.Warning(cn.line, fmt.Sprintf("unrecognized key %q", cn.name))

config/validate/rules_test.go

@@ -119,6 +119,15 @@ func TestCheckStructure(t *testing.T) {
 			config: "coreos:\n  etcd:\n    discovery: good",
 		},
 
+		// Test for deprecated keys
+		{
+			config: "coreos:\n  etcd:\n    addr: hi",
+		},
+		{
+			config:  "coreos:\n  etcd:\n    proxy: hi",
+			entries: []Entry{{entryWarning, "deprecated key \"proxy\" (etcd2 options no longer work for etcd)", 3}},
+		},
+
 		// Test for error on list of nodes
 		{
 			config: "coreos:\n  units:\n    - hello\n    - goodbye",