params nested in layer not supported

[mattijn]

Raised in vega/altair#2517 (comment)

The params property defined within a layer object is not resolving OK:

{
  "layer": [
    {
      "data": {
        "url": "https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/cars.json"
      },
      "mark": "circle",
      "encoding": {
        "x": {"field": "Miles_per_Gallon", "type": "quantitative"},
        "y": {"field": "Horsepower", "type": "quantitative"}
      }
    },
    {
      "params": [
        {
          "name": "variable001",
          "bind": {"input": "range", "max": 50, "min": 0, "step": 1},
          "value": 25
        }
      ],
      "data": {"name": "empty"},
      "mark": {"type": "rule", "size": 2, "strokeDash": [12, 6]},
      "encoding": {
        "x": {"datum": {"expr": "variable001"}, "type": "quantitative"}
      }
    }
  ],
  "$schema": "https://vega.github.io/schema/vega-lite/v5.1.0.json",
  "datasets": {"empty": [{}]}
}

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But when the same params property is placed on top-level it functions OK:

{
  "params": [
    {
      "name": "variable001",
      "bind": {"input": "range", "max": 50, "min": 0, "step": 1},
      "value": 25
    }
  ],
  "layer": [
    {
      "data": {
        "url": "https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/cars.json"
      },
      "mark": "circle",
      "encoding": {
        "x": {"field": "Miles_per_Gallon", "type": "quantitative"},
        "y": {"field": "Horsepower", "type": "quantitative"}
      }
    },
    {
      "data": {"name": "empty"},
      "mark": {"type": "rule", "size": 2, "strokeDash": [12, 6]},
      "encoding": {
        "x": {"datum": {"expr": "variable001"}, "type": "quantitative"}
      }
    }
  ],
  "$schema": "https://vega.github.io/schema/vega-lite/v5.1.0.json",
  "datasets": {"empty": [{}]}
}

Open the Chart in the Vega Editor

I can imagine this can be considered a bug on the Vega-Lite side, but not 100% sure.

[arvind]

Thanks for reporting the issue, @mattijn! As we were discussing in #8230, only selection parameters can be nested within views. Variable parameters can only be defined at the top-level. Our typings were incorrect in this regard. I've made them more precise in #8304.

[vega-org-bot]

🚀 Issue was released in v5.3.1-next.2 🚀