Deserialization of enums with enum values annotated with the same @JsonProperty value leads to InvalidDefinitionException: Multiple fields representing property

[noahzuch]

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Describe the bug

I'm using a thirdparty client that is deserializing json where in an enum multiple values are annotated with the same @JsonProperty value. When upgrading our dependencies from Jackson 2.15.4 to 2.17.1 (via Spring Boot 3.3.1) this API started failing with:
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Multiple fields representing property ...

This issue seems similar to #4409, but is still present in 2.16.2.

Version Information

2.16.2 to 2.17.1

Reproduction

I modified the example in #4409 to use @JsonProperty

public static class Bug {
        public enum ColorMode {
            @JsonProperty("RGB")
            RGB,
            @JsonProperty("RGBA")
            RGBa,
            @JsonProperty("RGBA")
            RGBA
        }
        public ColorMode colorMode;
    }

    @Test
    public void enumFails() throws Exception {
        String json = "{ \"color_mode\": \"RGBA\"}";
        ObjectMapper mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);
        mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        Bug bug = mapper.readValue(json, Bug.class);
        System.out.println(bug.colorMode);
    }

Expected behavior

Whether or not the old behaviour is expected, i can not tell. All I know is that in 2.15.4 it seems like the last enum property with the given @JsonProperty is used. So when execution the code above, the value RGBA is printed in the console. When switching the order of RGBA und RGBa, then RGBa is printed.

The current behaviour in 2.16.2 up to 2.17.1 is an exception when deserializing saying:
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Multiple fields representing property "RGBA": my.package.Temp$Bug$ColorMode#RGBA vs my.package.Temp$Bug$ColorMode#RGBa at [Source: REDACTED (StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION disabled); line: 1, column: 1]

Additional context

No response

[pjfanning]

Why do you have @JsonProperty("RGBA") on 2 different enum values? How is Jackson supposed to decide between the 2 enum values when you say that the same JSON input maps to 2 different enum values?

[noahzuch]

The example above is not production code. We depend on a separate library internal to our company. There, they use this to serialize two enum values to the same string, I guess (I will report why they use this once I get an answer from them). Im not sure if the old behaviour is by design or just a coincidence. Nevertheless it is a breaking change to 2.15.4

[pjfanning]

The new code seems more correct. We cannot deserialize properly if 2 enum values have the same text representation.
I guess you can still serialize with that set up but we are talking about deserialization.

My vote would be to keep the new code as is.

[cowtowncoder]

I agree: there is a genuine conflict. While I can see why for serialization-only use case someone might want to have 2 enum choices serialize into same String, this is currently not supported; and I am not sure it could be like this, given that @JsonProperty also affects deserialization where ambiguity occurs.
Use of @JsonGetter("name") would be less ambiguous and perhaps workable, although I don't think it would avoid the exception currently.

[noahzuch]

A team member responsible for this internal library will comment here why they used this functionality exactly. From my point of view as the creator of this issue I am also happy with the current behaviour in 2.16.2 upwards.

[cowtowncoder]

@noahzuch That would be interesting to hear about. And even if the new behavior were to remain, it is good there is a report for this change in case someone else is affected.