cmd: Fix validate command when JSON contains "@id" fields

Also, don't run admin server when validating...

admin.go

@@ -734,6 +734,20 @@ traverseLoop:
 	return nil
 }
 
+// RemoveMetaFields removes meta fields like "@id" from a JSON message.
+func RemoveMetaFields(rawJSON []byte) []byte {
+	return idRegexp.ReplaceAllFunc(rawJSON, func(in []byte) []byte {
+		// matches with a comma on both sides (when "@id" property is
+		// not the first or last in the object) need to keep exactly
+		// one comma for correct JSON syntax
+		comma := []byte{','}
+		if bytes.HasPrefix(in, comma) && bytes.HasSuffix(in, comma) {
+			return comma
+		}
+		return []byte{}
+	})
+}
+
 // AdminHandler is like http.Handler except ServeHTTP may return an error.
 //
 // If any handler encounters an error, it should be returned for proper

caddy.go

@@ -153,16 +153,7 @@ func changeConfig(method, path string, input []byte, forceReload bool) error {
 	// (an alternate way to do this would be to delete them from
 	// rawCfg as they are indexed, then iterate the index we made
 	// and add them back after encoding as JSON)
-	newCfg = idRegexp.ReplaceAllFunc(newCfg, func(in []byte) []byte {
+	newCfg = RemoveMetaFields(newCfg)
-		// matches with a comma on both sides (when "@id" property is
-		// not the first or last in the object) need to keep exactly
-		// one comma for correct JSON syntax
-		comma := []byte{','}
-		if bytes.HasPrefix(in, comma) && bytes.HasSuffix(in, comma) {
-			return comma
-		}
-		return []byte{}
-	})
 
 	// load this new config; if it fails, we need to revert to
 	// our old representation of caddy's actual config
@@ -295,10 +286,12 @@ func run(newCfg *Config, start bool) error {
 	var err error
 
 	// start the admin endpoint (and stop any prior one)
+	if start {
 		err = replaceAdmin(newCfg)
 		if err != nil {
 			return fmt.Errorf("starting caddy administration endpoint: %v", err)
 		}
+	}
 
 	if newCfg == nil {
 		return nil

cmd/commandfuncs.go

@@ -465,6 +465,8 @@ func cmdValidateConfig(fl Flags) (int, error) {
 		input = adaptedConfig
 	}
 
+	input = caddy.RemoveMetaFields(input)
+
 	var cfg *caddy.Config
 	err = json.Unmarshal(input, &cfg)
 	if err != nil {