Deserializing into jakarta.json.JsonObject accepts non-object JSON values

[g-tom]

Describe the bug
Jsonb.fromJson(v.toString(), JsonObject.class) works for v of type jakarta.json.JsonValue, regardless of whether it represents a JSON object or not.

To Reproduce

final JsonValue jsonString = Json.createValue("test");
final JsonValue jsonNumber = Json.createValue(1);
Jsonb jsonb = JsonbBuilder.create();
for (JsonValue v : List.of(jsonString, jsonNumber, JsonValue.TRUE, JsonValue.EMPTY_JSON_ARRAY)) {
    // Non-object JSON input is "mapped" to JsonObject
    JsonValue o = jsonb.fromJson(v.toString(), JsonObject.class);
    /*
       "test" (class org.eclipse.parsson.JsonStringImpl)
       1 (class org.eclipse.parsson.JsonNumberImpl$JsonIntNumber)
       true (class jakarta.json.JsonValueImpl)
       [] (class org.eclipse.parsson.JsonArrayBuilderImpl$JsonArrayImpl)
     */
    System.out.printf("%s (%s)\n", o, o.getClass());

    // JSON Processing equivalent fails as expected
    Assert.assertThrows(JsonParsingException.class,
        () -> Json.createReader(new StringReader(v.toString())).readObject());
}

Expected behavior
Deserializing into JsonObject should be possible only for object input. As per specification, the result should be the same as what is obtained with jakarta.json.JsonReader.

System information:

• OS: Linux
• Java Version: 17
• Wildfly Version: 36.0.1
• Yasson Version: 3.0.4

Additional context
Since the runtime type of the deserialized object represents arbitrary JSON, ClassCastExceptions can occur, e.g. if the deserialized result is assigned to a variable of type jakarta.json.JsonObject.

[g-tom]

@Verdent, @m0mus, do you agree this should be considered a bug? Would you mind commenting on #680?

[greek1979]

IMHO the reasoning is solid and the problem is evident. I agree that this is a bug, BUT there might be folks out there who actually (already) depend on this erroneous behaviour of Eclipse Yasson... Not that it makes such a behaviour valid and correct, but something to consider. Like, tie the fix for this issue to some bigger Yasson release, maybe?