JsonStringEnumConverter always returns a default value

[karatakos]

Description

When deserialising JSON containing a string that needs to be converted to an enum via JsonStringEnumConverter, the converter always deserialises with the first value of the enum.

Reproduction Steps

    [Test]
    public void JsonEnumStringConverterTest() {
        const string json = 
        """
        { 
            "foo": 0,
            "bar": "secondvalue"
        }
        """;

        var opts = new JsonSerializerOptions();

        opts.Converters.Add(new JsonStringEnumConverter());

        var value = JsonSerializer.Deserialize<SomeType>(json, opts);

        value.Bar.Should().Be(Enum.Parse<SomeTypeEnum>("secondvalue", ignoreCase: true));
    }

    public record SomeType(int Foo, SomeTypeEnum Bar);

    public enum SomeTypeEnum {
        FirstValue,
        SecondValue
    }

Expected behavior

Bar should be SecondValue

Actual behavior

Bar is FirstValue

Regression?

No response

Known Workarounds

No response

Configuration

8.0.201
MacOS 14.2.1 (23C71)

Other information

No response

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[gregsdennis]

Related: #74385

[gregsdennis]

Why does your assertion use Enum.Parse() instead of just SomeEnumType.SecondValue directly?

I don't expect it should change the outcome, but it's probably better to eliminate the chance that it does.

[karatakos]

Why does your assertion use Enum.Parse() instead of just SomeEnumType.SecondValue directly?

I don't expect it should change the outcome, but it's probably better to eliminate the chance that it does.

Thanks for the quick response. It's only there to show the string can be correctly parsed. Changing it to SomeTypeEnum.SecondValue will produce the same outcome.

[gregsdennis]

I think the simpler test more clearly identifies the troublesome code.

But your response above clears things up. Thanks for the clarity.

[elgonzo]

Your problem is not with JsonStringEnumConverter, nor with enums. Set the "foo" property in your json example to an integer value different from zero, and you might notice that deserializing "foo" also doesn't seem to work. (You see Foo == 0 in the deserialized record because 0 is the default value for the int type and not because it was taken from the json data.)

The reason is that by default STJ treats property names in a case-sensitive manner, therefore the json property names do not match the names of the record members, e.g., "foo" != "Foo" and "bar" != "Bar". To enable case-insensitive property name handling, set JsonSerializerOptions.PropertyNameCaseInsensitive to true and Bob's your uncle...

[karatakos]

@elgonzo you're right, thank you I had no idea. Apologies, I'll close this ticket.