chore: disallow empty proxy-server-nameserver when proxy-server-nameserver-policy is set

Author: wwqgtxx

config/config.go

@@ -1408,6 +1408,9 @@ func parseDNS(rawCfg *RawConfig, ruleProviders map[string]P.RuleProvider) (*DNS,
 	if dnsCfg.ProxyServerPolicy, err = parseNameServerPolicy(cfg.ProxyServerNameserverPolicy, ruleProviders, false, cfg.PreferH3); err != nil {
 		return nil, err
 	}
+	if len(dnsCfg.ProxyServerPolicy) != 0 && len(dnsCfg.ProxyServerNameserver) == 0 {
+		return nil, errors.New("disallow empty `proxy-server-nameserver` when `proxy-server-nameserver-policy` is set")
+	}
 
 	if dnsCfg.DirectNameServer, err = parseNameServer(cfg.DirectNameServer, false, cfg.PreferH3); err != nil {
 		return nil, err

docs/config.yaml

@@ -320,7 +320,7 @@ dns:
   # proxy-server-nameserver:
   #   - https://doh.pub/dns-query
   #   - tls://223.5.5.5:853
-  # proxy-server-nameserver-policy: # 格式同nameserver-policy，仅用于节点域名解析
+  # proxy-server-nameserver-policy: # 格式同nameserver-policy，仅用于节点域名解析，当且仅当proxy-server-nameserver不为空时生效
   #   'www.yournode.com': '114.114.114.114'
 
   # 专用于direct出口域名解析的 DNS 服务器，非必要配置项，如果不填则遵循nameserver-policy、nameserver和fallback的配置