[confgen] add a hacky approach to overwrite child config dns setups

conf-gen/generator/__init__.py

@@ -44,6 +44,7 @@ def generate_conf(
             if gen_info.get("base"):
                 gen = SingBoxGenerator.from_base(
                     base_object=generators[gen_info["base"]],
+                    dns=gen_info["dns"],
                     inbounds=gen_info["inbounds"],
                     route=gen_info["route"],
                     experimental=gen_info["experimental"],

conf-gen/generator/sing_box_generator.py

@@ -134,8 +134,16 @@ def _build_route(self):
 
     # TODO: Make this method more general and robust.
     @classmethod
-    def from_base(cls, base_object: Self, inbounds, route, experimental):
+    def from_base(cls, base_object: Self, dns, inbounds, route, experimental):
         new_object = copy(base_object)
+        # TODO: Define a former behavior of replacements and overwrites.
+        # `dns` only overwrites or appends DNS servers.
+        if dns.get("servers"):
+            old_servers = {s["tag"]: s for s in base_object.dns["servers"]}
+            for new_server in dns["servers"]:
+                tag = new_server["tag"]
+                old_servers.setdefault(tag, {}).clear()
+                old_servers[tag].update(new_server)
         new_object.inbounds = inbounds
         new_object.route.update(route)
         if experimental is None:

conf-gen/source.yaml

@@ -645,6 +645,11 @@ generates:
 - name: sing-box-clients
   type: sing-box
   base: *SING_BOX_CONF_BASE
+  dns:
+    servers:
+    - address: tls://1.12.12.12
+      detour: DIRECT
+      tag: DIRECT
   inbounds:
   - tag: tun
     type: tun