`Enum` values can not be read from single-element array even with `DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS`

[AndrejMitrovic]

Using Jackson 2.9.9.3.

This issue was carried over from micronaut-core: micronaut-projects/micronaut-core#8215

Example test-case:

package arrayissue;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.annotation.JsonCreator;

enum MyEnum {
    FOO("FOO"),
    BAR("BAR");

    private String value;

    MyEnum(String value) {
        this.value = value;
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper om = new ObjectMapper();
        om.enable(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS);
        System.out.println(om.readValue("\"FOO\"", MyEnum.class));
        System.out.println(om.readValue("[\"FOO\"]", MyEnum.class));
    }

    @JsonCreator
    public static MyEnum fromValue(String text) {
        System.out.println("-- CONVERTING FROM: " + text);
        return MyEnum.FOO;
    }
}

Result:

-- CONVERTING FROM: FOO
FOO
-- CONVERTING FROM: null
FOO

[AndrejMitrovic]

Added version info (2.9.9.3).

[cowtowncoder]

2.9.x is ancient version, will need to test against later (2.14.0). For now assuming problem still exists.

Root cause likely due to code not checking there is legit String value; nor considering unwrapping, so would need to add latter at least (and probably otherwise fail if String / number expected, Object/Array encountered).

[yawkat]

@cowtowncoder i think the same happens without UNWRAP_SINGLE_VALUE_ARRAYS, what should be the behavior then? i can work on this since it came up with micronaut.

[cowtowncoder]

@yawkat sounds good, I appreciate your help here -- it is/was on my short TODO-NEXT list :)