Stacked timeseries scale with parsing disabled throws TypeError

[TinfoilPancakes]

Expected Behavior

Should display a stacked timeseries chart with 1 or more datasets.

Current Behavior

Calls to Chart.update() fail resulting in Uncaught TypeError: Cannot read property 'length' of undefined

Full Trace:

Uncaught TypeError: Cannot read property 'length' of undefined
    at updateStacks (chart.js:2975)
    at BarController.parse (chart.js:3182)
    at BarController._resyncElements (chart.js:3491)
    at BarController.buildOrUpdateElements (chart.js:3137)
    at Chart.update (chart.js:6614)

Steps to Reproduce

Can be reproduced at https://www.chartjs.org/docs/latest/samples/scales/time-line.html

Steps:

• Open Javascript Console
• Under the Config tab add stacked: true to scales.y
• Under the Setup tab modify the dataset object with label: 'Dataset with point data' by adding parsing: false
• Replace the dataset's data with the following

data: [{
  x: Utils.newDate(0).getTime(),
  y: Utils.rand(0, 100)
}, {
  x: Utils.newDate(5).getTime(),
  y: Utils.rand(0, 100)
}, {
  x: Utils.newDate(7).getTime(),
  y: Utils.rand(0, 100)
}, {
  x: Utils.newDate(15).getTime(),
  y: Utils.rand(0, 100)
}]

• Click the Randomize action.

Context

Trying to improve performance for timeseries data with large sample counts - disabling parsing breaks the chart.

Environment

• Chart.js version: 3.11
• Browser name and version: Chrome 90.0.4430.72

Edit: Updated reproduction steps.

[kurkle]

The sample uses date strings. Values need to be in the internal format of the scale for chart to work without parsing.

See https://www.chartjs.org/docs/latest/axes/cartesian/time.html#date-formats

[TinfoilPancakes]

My apologies, I was referring to the wrong page when writing the steps. However the bug is still reproducable.

Along with listed steps, replace the data of the last dataset with:

data: [{
  x: Utils.newDate(0).getTime(),
  y: Utils.rand(0, 100)
}, {
  x: Utils.newDate(5).getTime(),
  y: Utils.rand(0, 100)
}, {
  x: Utils.newDate(7).getTime(),
  y: Utils.rand(0, 100)
}, {
  x: Utils.newDate(15).getTime(),
  y: Utils.rand(0, 100)
}]

And it will throw exceptions.

[kurkle]

I think its because the stacks are build when parsing and are stored in the parsed data.
Not sure if we can support stacked charts with gained speed compared to parsing: true.