Error related to debug mode?

[Odalrick]

I'm getting this error when I try to use hot reloading:

Uncaught TypeError: can't access property "$", state is undefined
    $elm$browser$Debugger$Main$getLatestModel cart-widget.elm.js:19763
    wrapSubs cart-widget.elm.js:19778
    F2 cart-widget.elm.js:2872
    _Platform_initialize cart-widget.elm.js:4776
    _Platform_worker cart-widget.elm.js:4722
    F4 cart-widget.elm.js:2881
    init cart-widget.elm.js:5402
    initApp cart-widget.coffee:136
    <anonymous> cart-widget.coffee:465
    <anonymous> cart-widget.js.js:35501
    <anonymous> cart-widget.js.js:35503

I can't figure out what this error is telling me.

The compiled files are loaded one after another in the browser, so I don't think it is an execution order issue.

<script src="/js/cart-widget.elm.js"></script>
<script src="/js/cart-widget.js.js"></script>

I had it working before, but I tried enabling the debug mode; it failed and figured I'd work on that later once I got everything else working. I'm not sure if that is related to this issue.

I cant really see a way to "turn debug mode off" though. Will restarting elm-watch do it?

Some details that may be relevant:

cart-widget.coffee and cart-widget.js.js are the same file, webpack has compiled it and the original name is read from the source map in the backtrace. cart-widget.elm.js is the compiled Elm code.

I have a "backend" worker that maintains one state for the entire page and a few "frontend" apps that are just views. They send and receive messages through ports and the cart-widget.coffee is responsible for creating the different Elm apps and connecting them to each other.

Everything is served from docker and a Ruby on Rails app, but that should be irrelevant; the actual files are essentially served by a static file server, and the app doesn't get far enough to start failing http requests.

[lydell]

Hi!

I can't figure out what this error is telling me.

There was a crash in Elm’s compiled JS. That is not supposed to happen. Most likely it’s due to a bug in elm-watch triggered by some piece in your Elm code that I have never thought of before. It could also be due to a postprocess script. Do you use the “postprocess” feature of elm-watch?

I cant really see a way to "turn debug mode off" though.

It’s currently not possible to switch compilation mode when the app fails to initialize. (Maybe I can improve that, though.) A workaround is to delete elm-stuff/elm-watch/stuff.json, restart elm-watch and refresh the page.

---

Would you be able to share the broken cart-widget.elm.js with me somehow? Then I could debug it.

[Odalrick]

Would you be able to share the broken cart-widget.elm.js with me somehow?

Yes, on Monday, when I get back to the computer.

And no postprocess script. I was thinking of adding one to see if that helped work around this bug, but never got that far.

The only thing I can think of that's vaguely unique is having many instances of the same app running, but that's never been a problem before. Besides, that's not the app that's crashing; it's a Platform.worker. It doesn't have any UI.

I'm planning on moving it to a web worker, mostly to handle multiple tabs.

[Odalrick]

This is the elm-watch.json.

{
  "targets": {
    "CartWidget": {
      "inputs": ["elm/CartWidget.elm", "elm/CartViews.elm"],
      "output": "public/js/cart-widget.elm.js"
    },
    "AdminOrder": {
      "inputs": ["elm/AdminOrder.elm"],
      "output": "public/js/admin-order.js"
    },
    "BookingWidget": {
      "inputs": ["elm/BookingWidget.elm"],
      "output": "public/js/booking-widget.elm.js"
    }
  },
  "port": 44331
}

Never got around to trying the other targets.

[lydell]

Which of the .elm files contains the Platform.worker? CartWidget.elm?

Not that you are not even supposed to be able to switch to debug mode for workers:

Edit: I managed to reproduce it now. It happens when one input (CartWidget.elm) is a Platform.worker and another input (CartViews.elm) is Browser.element, of the same target. Then it’s possible to enable the debugger (since one of the inputs can use it), but it causes a crash. Good catch!

[Odalrick]

Interesting. The way I usually build, the way I want to replace, is an npm script:

"elm-live elm/CartWidget.elm elm/CartViews.elm --no-server -- --debug --output=public/js/cart-widget.elm.js",

I wonder why that's never been a problem before.

[lydell]

Because you weren’t using elm-watch :) elm-watch has its own hot reloading implementation, and I introduced a bug when programs that do and do not support the debugger are bundled in the same output.

[Odalrick]

I got back and deleted the elm-stuff directoty, and it started working again. :)

I have the crashing file saved, but I don't suppose there is much point in posting it.

The tool itself looks great. Do one thing, and do it well. I'll configure the rest to work with my set up. 👍

[lydell]

Great, I’ll try to fix the bug soon!

[lydell]

Fix released in v1.1.1.