sile: make it easier to setup a modified luaEnv when writing documents

pkgs/by-name/si/sile/package.nix

@@ -110,41 +110,48 @@ stdenv.mkDerivation (finalAttrs: {
   enableParallelBuilding = true;
 
   passthru = {
-    luaEnv = lua.withPackages (
-      ps:
-      with ps;
+    # Use this passthru variable to add packages to your lua environment. Use
+    # something like this in your development environment:
+    #
+    # myLuaEnv = lua.withPackages (
+    #  ps: lib.attrVals (sile.passthru.luaPackages ++ [
+    #    "lua-cjson"
+    #    "lua-resty-http"
+    #  ]) ps
+    # )
+    luaPackages =
       [
-        cassowary
-        cldr
-        fluent
-        linenoise
-        loadkit
-        lpeg
-        lua-zlib
-        lua_cliargs
-        luaepnf
-        luaexpat
-        luafilesystem
-        luarepl
-        luasec
-        luasocket
-        luautf8
-        penlight
-        vstruct
+        "cassowary"
+        "cldr"
+        "fluent"
+        "linenoise"
+        "loadkit"
+        "lpeg"
+        "lua-zlib"
+        "lua_cliargs"
+        "luaepnf"
+        "luaexpat"
+        "luafilesystem"
+        "luarepl"
+        "luasec"
+        "luasocket"
+        "luautf8"
+        "penlight"
+        "vstruct"
         # lua packages needed for testing
-        busted
-        luacheck
+        "busted"
+        "luacheck"
         # packages needed for building api docs
-        ldoc
+        "ldoc"
         # NOTE: Add lua packages here, to change the luaEnv also read by `flake.nix`
       ]
       ++ lib.optionals (lib.versionOlder lua.luaversion "5.2") [
-        bit32
+        "bit32"
       ]
       ++ lib.optionals (lib.versionOlder lua.luaversion "5.3") [
-        compat53
-      ]
-    );
+        "compat53"
+      ];
+    luaEnv = lua.withPackages (ps: lib.attrVals finalAttrs.finalPackage.passthru.luaPackages ps);
 
     # Copied from Makefile.am
     tests.test = lib.optionalAttrs (!(stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isAarch64)) (