Can't set textVariableAnchorOffset with an expression via the JSON converter

[sargunv]

Describe the bug

MapLibre Compose uses MapLibre Native's Android/iOS JSON -> Expression converters to set layer properties. This works for most properties, but errors out on SymbolLayer.textVariableAnchorOffset. The error is different on iOS and Android:

Android: Nested literal arrays are not supported
iOS: -[NSConstantValueExpression getValue:]: unrecognized selector sent to instance 0x60000028c800

To Reproduce

On Android (Kotlin):

layer.setProperties(
  PropertyFactory.textVariableAnchorOffset(
    Expression.Converter.convert(
      JsonArray().apply {
        add("literal")
        add(JsonArray().apply {
          add("top")
          add(JsonArray().apply {
            add(0)
            add(1)
          })
          add("bottom")
          add(JsonArray().apply {
            add(0)
            add(-2)
          })
        })
      })
  )
)

On iOS (Kotlin via Obj-C interop)

layer.textVariableAnchorOffset =
  NSExpression.expressionWithMLNJSONObject(
    listOf(
      "literal", listOf(
        "top",
        NSValue.valueWithCGVector(
          CGVectorMake(0.0, 1.0)
        ),
        "bottom",
        NSValue.valueWithCGVector(
          CGVectorMake(0.0, -2.0)
        ),
      )
    )
  )

Expected behavior

Setting the value via the JSON converter should work the same as via literal/expressionForConstantValue.

Platform information:

• maplibre-android-sdk = "11.7.1"
• maplibre-ios = "6.9.0"

Additional context

Slack thread: https://osmus.slack.com/archives/C02B2CBSNBU/p1734582889691469

Interestingly, setting the value with a literal expression does work:

On Android:

layer.setProperties(
  PropertyFactory.textVariableAnchorOffset(
    Expression.literal(
      arrayOf(
        "top",
        arrayOf(0, 1),
        "bottom",
        arrayOf(0, -2)
      )
    )
  )
)

on iOS: similar, but with NSExpression.expressionForConstantValue.