Array index missing in path of JsonMappingException for Collection<String>, with custom deserializer

[joca-bt]

In some situations the path of a JsonMappingException doesn't contain the array index where the error occurred.

In the following example we have a custom string deserializer which is disabling the automatic casting from other types (#796).

try {
    mapper.readValue("{ \"array\": [ \"foo\", true ]}", Foo.class);
} catch (JsonMappingException exception) {
    System.out.println(exception); // 1
    for (var node : exception.getPath()) {
        System.out.println(node); // 2
        System.out.println(node.getFieldName()); // 3
        System.out.println(node.getIndex()); // 4
    }
}

public class Foo {
    public List<String> array;
}

public class StringDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser parser, DeserializationContext context) throws IOException {
        if (parser.hasToken(JsonToken.VALUE_STRING)) {
            return parser.getText();
        } else {
            throw context.wrongTokenException(parser, String.class, JsonToken.VALUE_STRING, "");
        }
    }
}

1: com.fasterxml.jackson.databind.exc.MismatchedInputException: Unexpected token (VALUE_TRUE), expected VALUE_STRING:
 at [Source: (String)"{ "array": [ "foo", true ]}"; line: 1, column: 21] (through reference chain: Foo["array"])
2: Foo["array"]
3: array
4: -1

In this case, there's no information about the array index in which the error is originating, since the path only has 1 node (it should have two like below).

In other situations we do, for example:

"{ \"array\": [ true, 1 ]}"

public class Foo {
    public List<Boolean> array;
}

1: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot coerce Number (1) for type `java.lang.Boolean` (enable `MapperFeature.ALLOW_COERCION_OF_SCALARS` to allow)
 at [Source: (PushbackInputStream); line: 2, column: 27] (through reference chain: Foo["array"]->java.util.ArrayList[1])
2: Foo["array"]
3: array
4: -1
2: java.util.ArrayList[1]
3: null
4: 1

Is there something different when using custom deserializers?

[cowtowncoder]

No, location tracking should work the same way... but it is possible that something in deserializer for List<Object> is different from that of more specialized List<String> (internally there is optimized handler for second case).
So it sounds like a bug. Thank you for reporting this!

[cowtowncoder]

Ok so... deserializers do need to add try-catch block to include location information, and this was missing from one code path of StringCollectionDeserializer. I added handling, but do not have a good unit test; would be nice to have, but for now location information can be seen from sample given. Fix will be in 2.10.1.