How to colorize a variable definition?

[ceving]

I try to create a theme, which mimics an Emacs style. In Emacs the definition of a variable gets colorized but not its usage. For example in the following code

const isplainobject = (arg) => {
  if (arg) {
    const c = arg.constructor;
    if (c === undefined) return true;
    if (c === Object) return true;
  }
  return false;
};

the identifiers following const (isplainobject and c) do have a color, but the cs in the if-conditions do not have a color.

How can this be specified in the style?

[ceving]

ChatGPT thinks Bat can not do this, because the babel-sublime syntax definition used by Bat is not able to recognize a declaration. Is this correct?

I was searching: https://github.com/babel/babel-sublime/blob/f4579f9107996c16208466248a85dc2296083a5f/JavaScript%20(Babel).YAML-tmLanguage

And I found the scope variable.parameter.function.js which works for the declaration of function parameters. But I can not find anything similar for var, const and let.

[keith-hall]

It looks like this syntax definition scopes variables as variable.other.readwrite.js: https://github.com/sharkdp/bat/blob/master/assets/syntaxes/02_Extra/JavaScript%20(Babel).sublime-syntax#L1157-L1158
but it doesn't give a different scope when immediately following let or const or var, so to achieve different highlighting in those places the syntax definition would need to be modified first...

[minanagehsalalma]

Not with the theme alone. In bat, the theme only colors the scopes that the syntax grammar emits. So if the JavaScript syntax definition does not give const isplainobject = ... a different scope from later usages of isplainobject, there is nothing for the theme to distinguish.

So the practical answer is:

• theme change only: no, that is not enough
• syntax grammar change: yes, if the grammar can mark declarations and references with different scopes

That matches what you found in the Babel/Sublime syntax. variable.parameter.function.js exists because function parameters already get a dedicated scope, but const / let / var declarations are not necessarily exposed with a separate scope that a .tmTheme can target.

If you want Emacs-style declaration-only coloring, you would need to modify or replace the JavaScript .sublime-syntax / tmLanguage used by bat, then rebuild the cache. If the upstream syntax package cannot express that distinction, bat will not be able to do it just by changing the theme.