Grid lines do not respond to tickMinStep

[morberg]

Grid lines do not respond to tickMinStep. Originally reported in vega/altair#2329

In August 2019 it seems the grid lines were removed (not sure what exact version of vega-lite Altair was using at that time).

Here is a small example that shows the problem. I would expect the grid lines without tick marks to be removed in this chart.

Open the Chart in the Vega Editor

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "description": "A simple bar chart with embedded data.",
  "data": {
    "values": [
      {"a": "A", "b": 2}, {"a": "B", "b": 1}, {"a": "C", "b": 1},
      {"a": "D", "b": 1}, {"a": "E", "b": 2}, {"a": "F", "b": 2},
      {"a": "G", "b": 3}, {"a": "H", "b": 3}, {"a": "I", "b": 1}
    ]
  },
  "mark": "bar",
  "encoding": {
    "x": {"field": "a", "type": "nominal", "axis": {"labelAngle": 0}},
    "y": {"field": "b", "type": "quantitative", "axis": {"tickMinStep": 1}}
  }
}