How i stop Vegalite to rounding of y axis Tick label

I am creating a chart in which i want axis values should be same digit after decimal point as in data , i want this data driven .

I know format in axis but i want to avoid this because it create view like repetative on axis . Is there any way without use of format.

Editor link

I want data driven same upto decimal point as in data because sometime data come upto 2 decimal value and sometime four decimal value

Expected Output

I make this using format but i want this same number of digit as in data (dynamic data driven )

for another use case desire output

Editor Link for Second case senerio

This is non trivial and you still have to use the format expression to get it working. In the example below, I take the first value in your dataset(provided as a string) and use the number of decimal places to specify the format string dynamically. Try changing the first row from 1.000 to 1.0000 for instance.

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A simple bar chart with embedded data.",
  "background": "white",
  "padding": 5,
  "height": 200,
  "style": "cell",
  "data": [
    {
      "name": "source_0",
      "values": [
        {"a": "A", "b": "1.000"},
        {"a": "B", "b": 2},
        {"a": "C", "b": 3},
        {"a": "D", "b": 4},
        {"a": "E", "b": 5},
        {"a": "F", "b": 6},
        {"a": "G", "b": 7},
        {"a": "H", "b": 8},
        {"a": "I", "b": 9}
      ]
    },
    {
      "name": "data_0",
      "source": "source_0",
      "transform": [
        {
          "type": "stack",
          "groupby": ["a"],
          "field": "b",
          "sort": {"field": [], "order": []},
          "as": ["b_start", "b_end"],
          "offset": "zero"
        },
        {
          "type": "filter",
          "expr": "isValid(datum[\"b\"]) && isFinite(+datum[\"b\"])"
        }
      ]
    }
  ],
  "signals": [
    {"name": "test", "update": "length(split(toString(data('source_0')[0]['b']),'.')[1])"},
    {"name": "x_step", "value": 20},
    {
      "name": "width",
      "update": "bandspace(domain('x').length, 0.1, 0.05) * x_step"
    }
  ],
  "marks": [
    {
      "name": "marks",
      "type": "rect",
      "style": ["bar"],
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "bar"},
          "description": {
            "signal": "\"a: \" + (isValid(datum[\"a\"]) ? datum[\"a\"] : \"\"+datum[\"a\"]) + \"; b: \" + (format(datum[\"b\"], \".3f\"))"
          },
          "x": {"scale": "x", "field": "a"},
          "width": {"signal": "max(0.25, bandwidth('x'))"},
          "y": {"scale": "y", "field": "b_end"},
          "y2": {"scale": "y", "field": "b_start"}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "band",
      "domain": {"data": "data_0", "field": "a", "sort": true},
      "range": {"step": {"signal": "x_step"}},
      "paddingInner": 0.1,
      "paddingOuter": 0.05
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {"data": "data_0", "fields": ["b_start", "b_end"]},
      "range": [{"signal": "height"}, 0],
      "nice": true,
      "zero": true
    }
  ],
  "axes": [
    {
      "scale": "y",
      "orient": "left",
      "tickRound": false,
      "gridScale": "x",
      "grid": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "a",
      "labelAngle": 90,
      "labelAlign": "left",
      "labelBaseline": "middle",
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "b",
      "format": {"signal": "'.'+test+'f'"},
      "tickRound": false,
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "zindex": 0
    }
  ]
}