`YearKeyDeserializer` doesn't work with non-padded year values

[sladkoff]

Description & proposal

The YearKeyDeserializer is unable to deserialize keys that are not in the format yyyy (e.g. "1"). It expects the year to be padded with zeros ("0001").

In contrast, the YearDeserializer is in fact working correctly and can handle non-padded values as well.

This could probably be fixed by changing the YearKeyDeserializer#deserialize:30 to something like this (we've currently registered a custom deserializer that does this):

@Override
protected Year deserialize(String key, DeserializationContext ctxt) throws IOException {
-    try {
-        return Year.parse(key, FORMATTER);
+        return Year.of(Integer.parseInt(key));
-    } catch (DateTimeException e) {
-        return _rethrowDateTimeException(ctxt, Year.class, e, key);
-    }
}

Steps to reproduce

Here's a simple test to demonstrate the behavior:

private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper().registerModule(new JavaTimeModule());

@Test
public void serializeAndDeserializeYearKey() throws IOException {
    Map<Year, Float> testMap = Collections.singletonMap(Year.of(1), 1F);

    String serialized = OBJECT_MAPPER.writeValueAsString(testMap);

    TypeReference<Map<Year, Float>> yearFloatTypeReference = new TypeReference<Map<Year, Float>>() {};

    Map<Year, Float> deserialized = OBJECT_MAPPER.readValue(serialized, yearFloatTypeReference);

    assertThat(deserialized).isEqualTo(testMap);
}

The above will throw java.time.format.DateTimeParseException: Text '1' could not be parsed at index 0

[cowtowncoder]

Thank you for reporting this, sounds like a bug indeed.

[cowtowncoder]

Marking as easy so new contributors could have a look.

One comment on solution: note that keys can only be Strings, whereas JSON values can be numbers, so handling is bit different by necessity. Still, solution as suggested above may be fine as long as it reports good parse exception for non-integer values.

[cowtowncoder]

Merged the fix, thank you @kupci for fixing as per @sladkoff's suggestion. Will be in 2.10.0 official (or, pr3, if such is released).