@Test
public void justThrowErrorEvenWithValidFormat() throws Exception
{
    SimpleModule module = new SimpleModule("test");
    module.addDeserializer(Bar.class,
            new FunctionalScalarDeserializer<>(Bar.class, (p, ctx) -> {
                // 1) Blindly throw user/business exception
                throw new IllegalArgumentException(
                        "BiFunction error: " + p.getValueAsString());
            }));

    ObjectMapper mapper = jsonMapperBuilder()
            .addModule(module)
            .build();

    try {
        // 2) JSON input is fully valid
        mapper.readValue("{\"bar\":\"fieldValue\"}", BarWrapper.class);
        fail();
    } catch (InvalidFormatException e) {
        // 3) Jackson wraps the exception as InvalidFormatException
        verifyException(e, "Cannot deserialize");
    }
}

/**
 * A general-purpose deserializer that uses a {@link Function} or {@link BiFunction}
 * to convert JSON scalar values (strings, numbers, booleans) into target type instances.
 * <p>
 * This deserializer is primarily designed for String-based conversions but also
 * supports other JSON scalar types via {@code getValueAsString()} coercion.
 * Non-scalar JSON values (arrays, objects, embedded objects) are rejected.
 * <p>
 * <b>Error handling guidelines:</b>
 * <ul>
 *   <li>Exceptions of type {@link com.fasterxml.jackson.databind.exc.InvalidFormatException}
 *       thrown by user code are treated as explicit signals of invalid input values
 *       and are propagated as-is.</li>
 *   <li>{@link com.fasterxml.jackson.databind.JsonMappingException} may be thrown by
 *       user code to indicate a deliberate mapping failure and will be propagated.</li>
 *   <li>Other runtime exceptions thrown by user code are considered application or
 *       domain failures and may be wrapped as {@link com.fasterxml.jackson.databind.JsonMappingException}
 *       rather than being reported as input-format errors.</li>
 * </ul>
 * <p>
 * Usage examples:
 * ...... rest omitted.....