Sometime between when `id: 39` and `id: 40` is created during `rawSpawn`
the `root` key in the object goes null. Still trying to find what code is
wiping it...
On Wednesday, August 3, 2016 at 12:21:18 PM UTC-6, OvermindDL1 wrote:
>
> The task object with `id: 39` does not have a null `root` at the time it
> is put into workQueue. At the time it is put into the workQueue it is:
> {callback : function(b), ctor: "_Task_andThen", task: {callback:
> function(callback), cancel: function(), ctor: "_Task_nativeBinding"}}
>
> The root.task.callback function seems to have one interesting closure that
> has a key/value of `navStart:1470247637381`, and there is another link in
> the cancel to the process with `id: 38` so it appears to be a
> continuation of that one. I am not sure of the internal structure of Elm
> so I am not sure what Native Binding it is called, and I use no Native
> Bindings in my project (only what comes with Elm core libraries is what
> exists here at all).
>
> A little further digging and I am seeing
> `_elm_lang$animation_frame$Native_AnimationFrame` in the stack, further
> digging makes it seem (although I am unsure) that the `root.task.callback`
> is the same function as defined at:
> https://github.com/elm-lang/animation-frame/blob/master/src/Native/AnimationFrame.js#L13
>
> I am not yet seeing how the `root` key on this "_Process" object is
> getting cleared yet before it has a chance to be processed, still tracing...
>
>
> On Wednesday, August 3, 2016 at 11:59:23 AM UTC-6, OvermindDL1 wrote:
>>
>> Debugged into it and caught the exception at the point to get the stack
>> values:
>> ```javascript
>> numSteps = 403
>> process = Object {ctor: "_Process", id: 39, root: null, stack: null,
>> mailbox: Array[0]}
>> ```
>> So root is null, why would it be trying to access a null value without
>> checking if null?
>>
>> Any ideas how to work around this in this project so I can at least keep
>> working in chrome?
>>
>>
>> On Wednesday, August 3, 2016 at 11:52:36 AM UTC-6, OvermindDL1 wrote:
>>>
>>> I keep getting this exception thrown from inside Elm, so far only from
>>> Chrome Version 51.0.2704.103 m
>>> ```
>>> elm.js:2417 Uncaught TypeError: Cannot read property 'ctor' of null
>>> ```
>>>
>>> Where that line and the surrounding context is purely Elm generated
>>> code, and is:
>>> ```javascript
>>> // STEP PROCESSES // Line 2411
>>>
>>> function step(numSteps, process)
>>> {
>>> while (numSteps < MAX_STEPS)
>>> {
>>> var ctor = process.root.ctor; // Line 2417 -- This is the error:
>>> Uncaught TypeError: Cannot read property 'ctor' of null
>>>
>>> if (ctor === '_Task_succeed')
>>> {
>>> while (process.stack && process.stack.ctor === '_Task_onError')
>>> {
>>> process.stack = process.stack.rest;
>>> }
>>> if (process.stack === null)
>>> ```
>>>
>>> The same javascript seems to run fine in firefox, IE, and edge, this
>>> only seems to happen in Chrome and only 'sometimes'. It seems to happen
>>> pretty quickly during loading and if it does not happen at the start then
>>> it does not seem to happen. I've not been able to find code to whittle
>>> down that lets my app still do anything while still causing this error.
>>>
>>> The 'step' function is being called from the 'work' function of (and
>>> with context):
>>> ```
>>> javascript
>>>
>>> // WORK QUEUE
>>>
>>> var working = false;
>>> var workQueue = [];
>>>
>>> function enqueue(process) {
>>> workQueue.push(process);
>>>
>>> if (!working) {
>>> setTimeout(work, 0);
>>> working = true;
>>> }
>>> }
>>>
>>> function work() {
>>> var numSteps = 0;
>>> var process;
>>> while (numSteps < MAX_STEPS && (process = workQueue.shift())) {
>>> numSteps = step(numSteps, process); // This is the place in the
>>> callstack before step
>>> }
>>> if (!process) {
>>> working = false;
>>> return;
>>> }
>>> setTimeout(work, 0);
>>> }
>>> ```
>>>
>>> Chrome is not reporting anything in the stack below `work` so this
>>> appears to be during the setTimeout callback set a few lines prior to work
>>> that calls work.
>>>
>>> Any thoughts as to the cause?
>>>
>>
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