Could it wait until a directory contains files i.e. not empty?

[bytrangle]

I want a build command to only run until a subdirectory contains files. Is it possible with wait-on?
Here is what worked:

"scripts" : {
  "start:clipper": "wait-on popup/build/js && npm run watch_clipper"
}

Hower, this didn't work:

"scripts" : {
  "start:clipper": "wait-on popup/build/* && npm run watch_clipper"
}

Even though the first one works, it's a little inflexible because the content of popup/build may change and no longer contains a js subdirectory.

[jeffbski]

We haven't built that feature in yet. It might be possible.