Unit deserialization does not work when unit or value are in lowercase

[dschuermans]

When providing a json such as this:

{ "unit": "LengthUnit.Meter", "value": 12 }

The TryDeserializeIComparable function fails because it attempts to find "Unit" and "Value" keys on the JToken.
JToken appears to be case sensitive so another way around it is to cast JToken to JObject and then use .GetValue(nameofValueUnit.Unit), StringComparison.OrdinalIgnoreCase)as per https://stackoverflow.com/questions/49886411/json-net-jtoken-keys-are-case-sensitive?noredirect=1&lq=1

Will post fix soon as i'm working on it right now

[dschuermans]

The following should do the trick 😄

 JToken token = JToken.Load(reader);

// See if it's an empty object
if (!token.HasValues)
{
      return null;
 }

JToken unit = ((JObject) token).GetValue(nameof(ValueUnit.Unit), StringComparison.OrdinalIgnoreCase);
 JToken value = ((JObject) token).GetValue(nameof(ValueUnit.Value), StringComparison.OrdinalIgnoreCase);

 if (unit == null || value == null)
{
      JsonSerializer localSerializer = new JsonSerializer()
      {
           TypeNameHandling = serializer.TypeNameHandling,
      };
      return token.ToObject<IComparable>(localSerializer);
}
else
{
     return new ValueUnit()
     {
         Unit = unit.ToString(),
         Value = value.ToObject<double>()
     };
}

Test that proves it:

[Fact]
public void CaseSensitivityForUnitOrValue_ExpectNoEffectOnDeserialization()
{
    string json = "{ \"unit\": \"LengthUnit.Meter\", \"value\": 12 }";

    Length result = DeserializeObject<Length>(json);

    Assert.NotNull(result);
    Assert.Equal(12, result.Meters);
}

[dschuermans]

Will add to #567

[angularsen]

Are you sure this is a good idea? I'm not sure, but I think we use standard behavior in JSON.net for parsing to UnitValue type, and I have a feeling JSON.net chose case sensitivity for a reason.

A quick google gives me:
https://stackoverflow.com/a/2738375/134761 linking to json-rpc spec
https://www.quora.com/Is-JSON-case-sensitive

[dschuermans]

Well, I just read through the RFC spec: https://tools.ietf.org/html/rfc8259

Can't find anything related to case sensitivity though... the RFC spec even has an example object that that has both pascal & camel cased properties.

Anyway, I just found it odd it wasn't working.. I spent a few years in the web app area, and when working in JavaScript with JSON, all properties were camelCased even though the properties on the ASP.NET web api were Pascal cased.

So yea, maybe you're right and shouldn't this be included.
Maybe I ought to test it first if I configure JSON.NET to use camelCasing when serializing / deserializing and see if that works.
But i have a feeling it won't, since the code is directly working with JToken's

I'll let you know what I find.

[dschuermans]

And here's Google take on JSON:

https://google.github.io/styleguide/jsoncstyleguide.xml?showone=Property_Name_Format#Property_Name_Format

[dschuermans]

@angularsen have a look at this:

As you can see, I configured my JSON.NET to camelCase properties. I then created a dummy object with 3 properties: a string, an int and a length property.
In the screenshot it clearly shows that my string, int and length properties are correctly serialized in camelCase, however the Length object itself is not serialized in camelCase but still Pascal case ☹️

[dschuermans]

Although I am starting to believe this might be an issue with JSON.NET itself as I can't see any code in the UnitsNetJsonConverter which could explain this behavior...

[dschuermans]

Hooray, figured it out 😄

Because the UnitsNetJsonConverter is a generic JsonConvert (i.e. there's no type specified for which the JsonConverter is used) it will be run against any type that's being serialized (which to me seems like a bad idea to begin with?)

So the first time around it will try to serialize a Unit, which in turn will tell the serializer to serialize a ValueUnitObject, which in turn calls the WriteJson method again on the converter.

Copying the ContractResolver from the original serializer solved the problem...

[angularsen]

Awesome! Nice find.

[dschuermans]

Sadly there doesn't seem to be a similar fix when reading json though ☹️
I'm still stuck with the case sensitivity there on JToken

[dschuermans]

@angularsen question though, I have wondered why there isn't some sort of IUnit interface that all units implement?
I'm pretty sure it would make this JSON conversion a lot more straight forward and I've had uses cases in the past where I wish i'd have such an interface, can't recall the exact scenarios atm though

Ah, I just found #371 😄

[angularsen]

We have IQuantity that Length, Mass etc implement. But we can't have IUnit, because that is currently an enum value (LengthUnit.Meter, MassUnit.Kilogram etc).

I'm sure we can improve IQuantity to make JSON serialization easier, any particular ideas you are thinking of?
Also, check out v4 branch as things have changed a bit there.

#487

[angularsen]

Any progress here? v4 is now released btw.

[dschuermans]

Nope, don't have time left after work & renovations at home i'm afraid :(
We still need to upgrade to v4 ourselves

[angularsen]

No problem, I'll close this issue for now just to clean up the issue list. Please reopen if you pick it up later.