anchor.diff:      let mkEntry = k: v: "${indent}${k} ${show v};";
       in concatStringsSep "\n" (mapAttrsToList mkEntry (explicit set));
   
  -  mkServer = name: text: ''
  +  mkServer = name: text: pkgs.writeText "nginx-${name}.conf" ''
  +    # ${name}:
       server {
       ${text}
       }
  
positive.code:       fastcgi_param HTTP_PROXY "";
        proxy_set_header Proxy "";
  
        ${concatStringsSep "\n" (mapAttrsToList mkServer cfg.http.servers)}
      }
    '';
  
  
negative.code: 
  let
  
    inherit (builtins)
      filter isBool toString ;
  
    inherit (lib)
      concatMapStrings concatStringsSep filterAttrs mapAttrsToList mkEnableOption
      mkIf mkOption ;
  
    inherit (lib.types)
      attrsOf bool either enum int lines nullOr path str submodule ;
  
  
    cfg = config.nixsap.apps.nginx;
    explicit = filterAttrs (n: v: n != "_module" && v != null);
  