[BUG] data[type=contour].autocontour not working with restyle

[mafar]

CodePen: https://codepen.io/mafar/pen/XWrxarp?editors=0010
This pen is bare minimum for bug reproduction

Explaination: https://plot.ly/javascript/reference/#contour
Initial data see below

1. Define data with autocontour:true
2. Define contours start,end and size option even they will be ignored because of autocontour:true

Once plot is drawn , restlye it with

var update = {
  autocontour: false,
  "contours.start": 3 
};
Plotly.restyle("myDiv", update, 0);

But plot does not update !!! as expected where it should have used contours.start end and size values

Code:

var data = [
  {
    z: [
      [10, 10.625, 12.5, 15.625, 20],
      [5.625, 6.25, 8.125, 11.25, 15.625],
      [2.5, 3.125, 5, 8.125, 12.5],
      [0.625, 1.25, 3.125, 6.25, 10.625],
      [0, 0.625, 2.5, 5.625, 10]
    ],
    type: "contour",
    ncontours: 15,
    autocontour: true,
    contours: {
      start: 1,
      end: 5,
      size: 1
    }
  }
];
var layout = {
  title: Contours"
};
Plotly.newPlot("myDiv", data, layout);
var update = {
  autocontour: false,
  "contours.start": 3 
};
Plotly.restyle("myDiv", update, 0);

[etpinard]

Writing down a similar play-by-play as in #4199 (comment) for this report:

Plotly.newPlot(gd, [
  {
    z: [
      [10, 10.625, 12.5, 15.625, 20],
      [5.625, 6.25, 8.125, 11.25, 15.625],
      [2.5, 3.125, 5, 8.125, 12.5],
      [0.625, 1.25, 3.125, 6.25, 10.625],
      [0, 0.625, 2.5, 5.625, 10]
    ],
    type: "contour",
    ncontours: 15,
    autocontour: true,
    contours: {
      start: 1,
      end: 5,
      size: 1
    }
  }
])

// gives (the auto contours)
gd.data[0].contours // => {start: 2, end: 18, size: 2}

// then
Plotly.restyle(gd, { autocontour: false, "contours.start": 3 })
// gives
gd.data[0].contours // => {start: 3, end: 18, size: 2}
// ... keeping the previous auto contours value and 
//     ignoring the starting {start: 1, end: 5, size: 1} settings

[etpinard]

As this bug has the same cause and will be solved at the same time as #4199 - I'll merge the two tickets together.

Thanks again @mafar for the very clear bug reports! Cheers

[mafar]

One additional comment:
Toggle of autocontour should work ,which it currently does not.
When i toggle autocontour Only, nothing happens in plotly , it should apply values based on this toggle

Turn on manual contour settings
js Plotly.restyle(gd, { autocontour: false })

Turn on autocontour which will consumencontours value (default is 15 anyway)
js Plotly.restyle(gd, { autocontour: true})