support list/array for datum for text encoding

[mattijn]

It would be great if "datum" within the text-encoding channel accepts a list/array as input as such ["text", "over", "multi-lines"].

If I try this within the editor then the chart renders successfully:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "data": {"values": [{}]},
  "mark": {"type": "text", "size": 14},
  "encoding": {
    "text": {"datum": ["text", "over", "multi-lines"]},
    "x": {"datum": 0, "scale": {"domain": [-1, 1]}},
    "y": {"datum": 0, "scale": {"domain": [-1, 1]}}
  }
}

Open the Chart in the Vega Editor

But the vega-lite grammar does currently not allow it:

With an validation warning stating:

[Warning] Validation: /encoding/text/datum must be number,string,boolean,null of #/definitions/PrimitiveValue/type
[Warning] Validation: /encoding/text/datum must be object of #/type
[Warning] Validation: /encoding/text/datum must be object of #/definitions/ExprRef/type
[Warning] Validation: /encoding/text/datum must be object of #/definitions/RepeatRef/type
[Warning] Validation: /encoding/text/datum must match a schema in anyOf of #/properties/datum/anyOf

[kanitw]

Some notes if someone wanna help fix this:

Relevant type definitions are

• TextDef https://github.com/vega/vega-lite/blob/main/src/channeldef.ts#L198, which imports Text from Vega.
• DatumDef, which seem to not accept string array yet