Filling line should be a macro to add an area layer?

[kanitw]

I think nobody really want this spec

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "Google's stock price over time.",
  "data": {"url": "data/stocks.csv"},
  "transform": [{"filter": "datum.symbol==='GOOG'"}],
  "mark": {"type": "line", "fill": "black"},
  "encoding": {
    "x": {"field": "date", "type": "temporal"},
    "y": {"field": "price", "type": "quantitative"}
  }
}

to look like this:

one may want something like this:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "Google's stock price over time.",
  "data": {"url": "data/stocks.csv"},
  "transform": [{"filter": "datum.symbol==='GOOG'"}],
  "mark": {"type": "area", "line": true, "fill": "black"},
  "encoding": {
    "x": {"field": "date", "type": "temporal"},
    "y": {"field": "price", "type": "quantitative"}
  }
}