Constraint-type contour plot cannot shade entire area

Steps to reproduce

Create plotly.js data object with the following:

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',
  colorscale: 'Jet',
    "contours": {
        "coloring": "lines",
        "operation": "][",
        "showlabels": true,
        "type": "constraint",
        "value": [0,20]
    },
}];

Here is a link to a CodePen that shows the problem. https://codepen.io/kfd182/pen/yLKvNLJ

Current behaviour (bug)

Empty plot

Expected behaviour (correct)

Plot that is entirely shaded in

Other comment

When making a contour plot that uses type=‘constraint’ and operation = ‘][’ , setting value = [data-min, data-max] creates an empty plot, instead of a completed shaded plot. If you adjust data-min to be slightly larger or adjust data-max to be slightly smaller, then you get a nearly completely shaded plot.

I think one workaround could be using {operation: '<', and value: data-min}. This will shade the entire plot area.

Reported by

kdaquila-questek

Inizia dalla riproduzione CodePen fornita e traccia la gestione dei contorni per l’operazione ][ con il valore [data-min, data-max]. Il lavoro è completato quando l’intero intervallo di dati viene renderizzato come un grafico ombreggiato invece che come un grafico vuoto, mentre i casi limite adiacenti continuano a comportarsi correttamente.