lib/lua: add isKeyword and isIdentifier

Allow testing whether a string is a valid lua identifier or a reserved
keyword.

lib/helpers.nix

@@ -10,10 +10,10 @@ let
   nixvimUtils = import ./utils.nix { inherit lib nixvimTypes _nixvimTests; };
   nixvimOptions = import ./options.nix { inherit lib nixvimTypes nixvimUtils; };
   nixvimDeprecation = import ./deprecation.nix { inherit lib; };
-  inherit (import ./to-lua.nix { inherit lib; }) toLuaObject;
 in
-{
+rec {
   maintainers = import ./maintainers.nix;
+  lua = import ./to-lua.nix { inherit lib; };
   keymaps = import ./keymap-helpers.nix { inherit lib nixvimOptions nixvimTypes; };
   autocmd = import ./autocmd-helpers.nix { inherit lib nixvimOptions nixvimTypes; };
   neovim-plugin = import ./neovim-plugin.nix {
@@ -26,7 +26,7 @@ in
   };
   vim-plugin = import ./vim-plugin.nix { inherit lib nixvimOptions nixvimUtils; };
   inherit nixvimTypes;
-  inherit toLuaObject;
+  inherit (lua) toLuaObject;
 }
 // nixvimUtils
 // nixvimOptions

lib/to-lua.nix

@@ -1,6 +1,37 @@
 { lib }:
 with lib;
 rec {
+  # Whether the string is a reserved keyword in lua
+  isKeyword =
+    s:
+    elem s [
+      "and"
+      "break"
+      "do"
+      "else"
+      "elseif"
+      "end"
+      "false"
+      "for"
+      "function"
+      "if"
+      "in"
+      "local"
+      "nil"
+      "not"
+      "or"
+      "repeat"
+      "return"
+      "then"
+      "true"
+      "until"
+      "while"
+    ];
+
+  # Valid lua identifiers are not reserved keywords, do not start with a digit,
+  # and contain only letters, digits, and underscores.
+  isIdentifier = s: !(isKeyword s) && (match "[A-Za-z_][0-9A-Za-z_]*" s) == [ ];
+
   # Black functional magic that converts a bunch of different Nix types to their
   # lua equivalents!
   toLuaObject =

tests/lib-tests.nix

@@ -6,6 +6,45 @@
   helpers,
 }:
 let
+  luaNames = {
+    # Keywords in lua 5.1
+    keywords = [
+      "and"
+      "break"
+      "do"
+      "else"
+      "elseif"
+      "end"
+      "false"
+      "for"
+      "function"
+      "if"
+      "in"
+      "local"
+      "nil"
+      "not"
+      "or"
+      "repeat"
+      "return"
+      "then"
+      "true"
+      "until"
+      "while"
+    ];
+    identifiers = [
+      "validIdentifier"
+      "valid_identifier"
+      "_also_valid_"
+      "_weirdNameFMT"
+    ];
+    other = [
+      "1_starts_with_digit"
+      "01234"
+      "12340"
+      "kebab-case"
+    ];
+  };
+
   results = pkgs.lib.runTests {
     testToLuaObject = {
       expr = helpers.toLuaObject {
@@ -114,6 +153,51 @@ let
       expected = ''{["c"] = { },["d"] = {["g"] = { }}}'';
     };
 
+    testIsLuaKeyword = {
+      expr = builtins.mapAttrs (_: builtins.filter helpers.lua.isKeyword) luaNames;
+      expected = {
+        keywords = [
+          "and"
+          "break"
+          "do"
+          "else"
+          "elseif"
+          "end"
+          "false"
+          "for"
+          "function"
+          "if"
+          "in"
+          "local"
+          "nil"
+          "not"
+          "or"
+          "repeat"
+          "return"
+          "then"
+          "true"
+          "until"
+          "while"
+        ];
+        identifiers = [ ];
+        other = [ ];
+      };
+    };
+
+    testIsLuaIdentifier = {
+      expr = builtins.mapAttrs (_: builtins.filter helpers.lua.isIdentifier) luaNames;
+      expected = {
+        keywords = [ ];
+        identifiers = [
+          "validIdentifier"
+          "valid_identifier"
+          "_also_valid_"
+          "_weirdNameFMT"
+        ];
+        other = [ ];
+      };
+    };
+
     testUpperFirstChar = {
       expr = map helpers.upperFirstChar [
         "foo"