Clojurians Log v2

I just set up a repro for something I observed with vega-lite.js, namely that shadow is unable to build it into a browser target. I would like to understand why that happens. npx shadow-cljs watch app

Failed to inspect file
  /.../repro/node_modules/vega-lite/build/vega-lite.js

Errors encountered while trying to parse file
  /home/rick/Software/repro/node_modules/vega-lite/build/vega-lite.js
  {:line 16106, :column 4, :message "'}' expected"}

The position in code of vega-lite.js

class Optimizer {
    #modified; // <-- this is line 16106
    constructor() {
      this.#modified = false;
    }

Google tells me those are ES2022 private class fields. I can find no mention of either in the shadow docs, the "most recent" option seems to be :es2020. So is this just a modern JS feature that the compiler can't handle? I have been using vega-lite in a project so far with no problems where the build target is :esm, which I ended up doing because it was the only way to integrate an external dependency, which I only got to work with the specific bundler used by the developers. This completely fried the REPL workflow (Vite that is, which apparently requires some extended rain dance to do hot module reloading), which I have decided is unacceptable. So I am trying to get back to a no-external bundler setup. I am kind of confused about when to use what kind of build target and what the respective implications are. For context: package.json

"dependencies": {
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "react-vega": "^7.6.0"
  }

shadow-cljs.edn

:dependencies
 [[reagent "1.1.1"]]

 :builds
 {:app {:target :browser
        :modules {:main {:entries [core]
                         :init-fn core/init}}}}}

core.cljs

(ns core
  (:require
   ["react-dom/client" :refer [createRoot]]
   [reagent.core :as r]
   ["react-vega" :refer [VegaLite]])) ;; not even using this

(defonce root
  (createRoot (.getElementById js/document "app")))

(defn mount-root
  []
  (.render root (r/as-element [:div "hi"])))

(defn init [] (mount-root))