Consider selecting `Mode.DELEGATING` for `Map`-valued 1-arg constructors

[cowtowncoder]

(note: created from FasterXML/jackson-module-kotlin#846)

1-argument constructors are fundamentally ambiguous: for example, POJO like:

public class Bean {
   @JsonCreator
   public Bean(String key) { ... }
}

could be expected to match either JSON String like

"value"

OR JSON Object

{ "key": "value" }

where first case is "Delegating" (full JSON value is Delegated as-is) and second case "Properties-based" (since incoming Object's property/properties are matched into separate properties -- 1-argumenet case is just a special case).

So Jackson has to use heuristics to decide which one to use. There are a few hints being checked (such as existence of @JsonValue strongly suggesting Delegating case; and existence of Field/setter/getter with name matching argument name suggesting Properties based case).

It sounds like behavior changed from 2.17 to 2.18, at least for Kotlin module, in a way that formerly Delegating cases were now decided as Properties-ones.
But it might be possible to change that heuristics such that if the parameter type is java.util.Map, chances are we have Delegating case (could extend to consider Collection and/or JsonNode as well).

[cowtowncoder]

I am unable to reproduce the problem, unfortunately. Map valued 1-param @JsonCreator annotated constructor is indeed detected as DELEGATING in most cases. Only exception is the case where there is public field with same name as implicit parameter to Map-valued argument.

Closing: will need actual reproduction, can't do anything without it.