static O hotwire_onCompile; // voidfunc(Pair<jarFile, transpiledSource>)
sbool hotwire_serially;
static Lock hotwire_overInternalBot_lock = lock();
sbool hotwire_compileOnServer;

static Class<?> hotwire_overInternalBot(S progID) {
  ret hotwire_overInternalBot(progID, "main");
}

static Class<?> hotwire_overInternalBot(S progID, S mainClass) {
  ret hotwire_overInternalBot(progID, _ -> mainClass);
}

static Class<?> hotwire_overInternalBot(S progID, IF1<ClassLoader, S> calculateMainClass) ctex {
  Pair<File, S> p;
  try {
    p = hotwire_compile(progID);
  } catch e {
    throw rethrow("Error hotwiring " + progID, e);
  }
  File jar = p.a;
  assertTrue(jar.getAbsolutePath(), jar.isFile());
  
  L<File> files = hotwire_collectJars(jar);

  // make class loader
  JavaXClassLoader classLoader = hotwire_makeClassLoader(files);
  classLoader.progID = progID;
  
  S mainClass = calculateMainClass == null ? "main" : calculateMainClass.get(classLoader);
  ret hotwire_finish(classLoader, progID, p.b, mainClass);
}

// returns pair(jar, transpiled src)
static Pair<File, S> hotwire_compile(S progID) {
  Pair<File, S> p = hotwire_compileOnServer && !isLocalSnippetID(progID)
    ? compileSnippetThroughServer(progID)
    : CompilerBot.compileSnippet2(progID);
  lock hotwire_serially ? hotwire_overInternalBot_lock : null;
  callF(hotwire_onCompile, p);
  ret p;
}

Began life as a copy of #1002246