Vaadin 25: JsonArray parameters in @ClientCallable methods fail to deserialize

[javier-godoy]

Describe the bug

Adding a child (or sibling) to a node in the Edit Chart demo fails on Vaadin 25 with a server-side deserialization error.

OrgChart declares @ClientCallable methods that take an elemental.json.JsonArray parameter:

• OrgChart#onChildrenAdded(String nodeId, JsonArray childIds)
• OrgChart#onSiblingsAdded(String nodeId, JsonArray siblingIds)

In Vaadin 25, RPC arguments are decoded with JacksonCodec, which cannot instantiate elemental.json.JsonArray (abstract type, no creators), so the invocation fails and the children/siblings are never added on the server side.

[qtp2075982863-59] ERROR com.vaadin.flow.server.DefaultErrorHandler - Unexpected error: Cannot deserialize JSON to type elemental.json.JsonArray: Cannot construct instance of `elemental.json.JsonArray` (no Creators, like default constructor, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [No location information]
java.lang.IllegalArgumentException: Cannot deserialize JSON to type elemental.json.JsonArray: Cannot construct instance of `elemental.json.JsonArray` (no Creators, like default constructor, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [No location information]
	at com.vaadin.flow.internal.JacksonCodec.decodeAs(JacksonCodec.java:259)
	at com.vaadin.flow.server.communication.rpc.DefaultRpcDecoder.decode(DefaultRpcDecoder.java:49)
	at com.vaadin.flow.server.communication.rpc.PublishedServerEventHandlerRpcHandler.decodeArg(PublishedServerEventHandlerRpcHandler.java:332)
	at com.vaadin.flow.server.communication.rpc.PublishedServerEventHandlerRpcHandler.decodeArgs(PublishedServerEventHandlerRpcHandler.java:268)
	at com.vaadin.flow.server.communication.rpc.PublishedServerEventHandlerRpcHandler.invokeMethod(PublishedServerEventHandlerRpcHandler.java:222)
	...
Caused by: tools.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `elemental.json.JsonArray` (no Creators, like default constructor, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [No location information]
	at tools.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:70)
	at tools.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1995)
	at tools.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:511)
	at tools.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1525)
	at tools.jackson.databind.deser.AbstractDeserializer.deserialize(AbstractDeserializer.java:254)
	at tools.jackson.databind.deser.DeserializationContextExt.readRootValue(DeserializationContextExt.java:266)
	at tools.jackson.databind.ObjectMapper._readValue(ObjectMapper.java:2610)
	at tools.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:978)
	at tools.jackson.databind.ObjectMapper.treeToValue(ObjectMapper.java:1291)
	at com.vaadin.flow.internal.JacksonCodec.decodeAs(JacksonCodec.java:255)
	... 58 more

Expected behavior

Adding a child/sibling to a node works without server-side errors on Vaadin 25.

The @ClientCallable methods should use a parameter type that Vaadin 25 can decode (e.g. com.fasterxml.jackson.databind.node.ArrayNode, or a plain int[]/Integer[]) instead of elemental.json.JsonArray.

Minimal reproducible example

1. Run the demo with the v25 profile.
2. Open the Edit Chart demo.
3. Add a child to a node.
4. The error above is logged in the server console.

Add-on Version

5.4.0-SNAPSHOT

Vaadin Version

25

Additional information

Reported by @paodb in #101 (review) — unrelated to that PR's changes.