Empty selections cannot be composed with "and" in a transform filter

[victornoel]

Here is an example

When you select:

• null (aka empty selection if I understood well), the whole dataset is kept
• a value for only one of the select input, the chart gets blank
• a value for both inputs, the filter is applied

I would expect that selecting a value for only one of the two inputs would filter according to this input.

Note that the same problem happens:

• without using the null value but only at first (because before the user touch the input, the selection is considered empty in the same way)
• when using multiple fields and bindings (select) in the same selection, but in that case, instead of getting a blank chart, we get all points.

{
  "$schema": "https://vega.github.io/schema/vega-lite/v3.4.0.json",
  "data": {
    "url": "https://vega.github.io/vega-datasets/data/cars.json"
  },
  "encoding": {
    "color": {
      "field": "Origin",
      "type": "nominal"
    },
    "tooltip": [
      {
        "field": "Name",
        "type": "nominal"
      },
      {
        "field": "Origin",
        "type": "nominal"
      },
      {
        "field": "Horsepower",
        "type": "quantitative"
      },
      {
        "field": "Miles_per_Gallon",
        "type": "quantitative"
      }
    ],
    "x": {
      "field": "Horsepower",
      "type": "quantitative"
    },
    "y": {
      "field": "Miles_per_Gallon",
      "type": "quantitative"
    }
  },
  "mark": {
    "type": "circle"
  },
  "selection": {
    "selector011": {
      "bind": {
        "input": "select",
        "options": [
          null,
          "USA",
          "Europe",
          "Japan"
        ]
      },
      "fields": [
        "Origin"
      ],
      "type": "single"
    },
    "selector012": {
      "bind": {
        "input": "select",
        "options": [
          null,
          8,
          4,
          6,
          3,
          5
        ]
      },
      "fields": [
        "Cylinders"
      ],
      "type": "single"
    }
  },
  "transform": [
    {
      "filter": {
        "selection": {
          "and": [
            "selector011",
            "selector012"
          ]
        }
      }
    }
  ]
}

[petermattia]

FYI - I have a toy example of this bug in this SO question

[jeremysalwen]

I am seeing this bug as well. Is there any workaround?

[drgould]

Moving the "and" outside of the selection is a workaround. Like so:

{
  "filter": {
    "and": [
      {"selection": "selection_1"},
      {"selection": "selection_2"}
    ]
  }
}

[arvind]

Thank you @victornoel for filing the issue, and @drgould for the workaround. This issue will be fixed with #7155, which standardizes the workaround by dropping support for logical compositions within a single "selection" property.