widget generated with vegaEmbed transform dates to numbers when exporting to vega editor

[mtiberghien]

Hi,

I've created a vega spec based on a small datasource where dates as written with the following form "yyyy-mm-dd" so that the spec date can be human readable.

The spec code is here.
The spec is embedded in a web page using https://cdn.jsdelivr.net/npm/vega-embed@6 script.
The page code is here.

The widget can be viewed here

My issue occurs when I'm using "View Source" or "Open in Vega Editor" which is provided in button created by vegaEmbed.

The dates in my datasource are now stored as timestamp and not string.
This breaks my spec because I was using a parser to convert my string dates.

Here is the code used in my spec (in data)

"data": [
    {
      "name":"dates",
      "format":{"parse":{"debut":"utc:%Y-%m-%d","fin":"utc:%Y-%m-%d"}},
      "values":[
        {"debut":"2022-11-7", "fin":"2022-11-7", "module":"Algorithmie", "code":9601, "type":"Environnement", "enseignant":"Didier Razon"},
        {"debut":"2022-11-8", "fin":"2022-11-8", "module":"Rôle et comportement du consultant", "code":6480, "type":"Comportement", "enseignant":"Sylvie Deprez"},
        {"debut":"2022-11-9", "fin":"2022-11-9", "module":"Algorithmie", "code":8082, "type":"Environnement", "enseignant":"Didier Razon"}]
    }]

Here is the code when viewing source or exporting in vega editor

  "data": [
    {
      "name": "dates",
      "format": {"parse": {"debut": "utc:%Y-%m-%d", "fin": "utc:%Y-%m-%d"}},
      "values": [
        {
          "debut": 1667779200000,
          "fin": 1667779200000,
          "module": "Algorithmie",
          "code": 9601,
          "type": "Environnement",
          "enseignant": "Didier Razon"
        },
        {
          "debut": 1667865600000,
          "fin": 1667865600000,
          "module": "Rôle et comportement du consultant",
          "code": 6480,
          "type": "Comportement",
          "enseignant": "Sylvie Deprez"
        },
        {
          "debut": 1667952000000,
          "fin": 1667952000000,
          "module": "Algorithmie",
          "code": 8082,
          "type": "Environnement",
          "enseignant": "Didier Razon"
        }]
    }]