add pipe, set, lset, require helpers

lib.nix

@@ -48,6 +48,7 @@ let
       # add an empty line at the end
       ++ [ (raw "") ]
     );
+  pipe = join ".";
 
   isRaw = expr: getType expr == "raw";
   raw = expr:
@@ -69,6 +70,10 @@ let
       ++ [ (join ", " args) ]
       ++ [ (raw ")") ]
     );
+  require = name: call "require" [ name ];
+
+  set = variable: value: join " = " [ (raw variable) value ];
+  lset = variable: value: join " " [ (raw "local") (set variable value) ];
 
   isLuaNil = expr: getType expr == "nil";
   LuaNil = { _type = "nil"; };
@@ -111,7 +116,6 @@ let
     else error "Value '${toString expr}' is not supported yet";
 
   toLua = val: toLuaInternal 0 val;
-
 in
 {
   # Deprecated
@@ -123,6 +127,6 @@ in
   inherit toLua;
 
   inherit LuaNil;
-  inherit raw join concat concatLines;
-  inherit call namedField;
+  inherit raw join concat concatLines pipe;
+  inherit namedField call require set lset;
 }

lib.test.nix

@@ -133,4 +133,19 @@ with nix2lua; pkgs.lib.runTests {
       bar("baz", "biz")
     '';
   };
+  "test returns a pipe with many function call" = {
+    expr = toLua (pipe [
+      (require "nvim-treesitter.parsers")
+      (call "get_parser_configs" [ ])
+    ]);
+    expected = "require(\"nvim-treesitter.parsers\").get_parser_configs()";
+  };
+  "test returns lua with setting value to the variable" = {
+    expr = toLua (set "parser_config.d2" { });
+    expected = "parser_config.d2 = {  }";
+  };
+  "test returns lua with setting value to the local variable" = {
+    expr = toLua (lset "parser_config.d2" { });
+    expected = "local parser_config.d2 = {  }";
+  };
 }