add join and mkCall

lib.nix

@@ -22,6 +22,11 @@ let
 
   warn = msg: builtins.trace "[nix2lua] warning: ${msg}";
 
+  isJoin = expr: getType expr == "_join";
+  join = sep: expr:
+    if isList expr then { _type = "_join"; sep = validString sep; parts = expr; }
+    else error "Value '${toString expr}' is not supported for a join type";
+
   isLuaRaw = expr: getType expr == "raw";
   mkLuaRaw = expr:
     if isLuaRaw expr then
@@ -31,10 +36,20 @@ let
     else
       error "Value '${toString expr}' is not supported for a raw type";
 
-  # mkCall = fnName: args: mkLuaRaw
+  mkCall = fnName: args:
+    let
+      luaFn =
+        if isString fnName && builtins.stringLength fnName > 0 then mkLuaRaw fnName
+        else error "Value '${toString fnName}' is not a valid function name";
+    in
+    join "" (
+      [ luaFn (mkLuaRaw "(") ]
+      ++ [ (join ", " args) ]
+      ++ [ (mkLuaRaw ")") ]
+    );
 
-  LuaNil = { _type = "nil"; };
   isLuaNil = expr: getType expr == "nil";
+  LuaNil = { _type = "nil"; };
 
   # DEPRECATED
   mkLuaNil = warn "`mkLuaNil` is deprecated. Use `LuaNil` instead" LuaNil;
@@ -53,7 +68,8 @@ let
 
   toLuaInternal = depth: expr:
     let nextDepth = depth + 1; in
-    if isLuaNil expr then "nil"
+    if isJoin expr then concatStringsSep expr.sep (map (toLuaInternal depth) expr.parts)
+    else if isLuaNil expr then "nil"
     else if isLuaRaw expr then expr.raw
     else if isNamedField expr then
       if depth > 0 then toLuaNamedField expr.name expr.value
@@ -86,8 +102,11 @@ let
     else error "Value '${toString expr}' is not a valid string";
 in
 {
+  # low-level
+  inherit join;
+
   inherit toLua;
-  inherit LuaNil mkLuaRaw mkNamedField;
+  inherit LuaNil mkLuaRaw mkNamedField mkCall;
   # DEPRECATED
   inherit mkLuaNil;
 }

lib.test.nix

@@ -18,7 +18,7 @@
 
 let
   nix2lua = import ./lib.nix;
-  inherit (nix2lua) toLua LuaNil mkLuaRaw mkNamedField;
+  inherit (nix2lua) toLua LuaNil mkLuaRaw mkNamedField mkCall;
   inherit (builtins) tryEval;
 
   failed = { success = false; value = false; };
@@ -120,4 +120,8 @@ pkgs.lib.runTests {
     expr = tryEval (toLua (mkNamedField "foo" "bar"));
     expected = failed;
   };
+  "test returns call function with arguments" = {
+    expr = toLua (mkCall "root_pattern" [ "deno.json" "deno.jsonc" ]);
+    expected = "root_pattern(\"deno.json\", \"deno.jsonc\")";
+  };
 }