DeserializeKeyValuePair - Should ignore "__type" property

grexican · November 19, 2020, 3:57pm

When serializing and then deserializing KVPs and emitting the Type information, if any key besides “key” or “value” is found, it throws. I think the code should ignore “__type”, no?

github.com

ServiceStack/ServiceStack.Text/blob/master/src/ServiceStack.Text/Common/DeserializeKeyValuePair.cs#L73


var keyValue = default(TKey);
var valueValue = default(TValue);


var valueLength = value.Length;
while (index < valueLength)
{
    var key = Serializer.EatMapKey(value, ref index);
    Serializer.EatMapKeySeperator(value, ref index);
    var keyElementValue = Serializer.EatTypeValue(value, ref index);


    if (key.CompareIgnoreCase("key".AsSpan()))
        keyValue = (TKey)parseKeyFn(keyElementValue);
    else if (key.CompareIgnoreCase("value".AsSpan()))
        valueValue = (TValue)parseValueFn(keyElementValue);
    else
        throw new SerializationException("Incorrect KeyValuePair property: " + key.ToString());


    Serializer.EatItemSeperatorOrMapEndChar(value, ref index);
}


return new KeyValuePair<TKey, TValue>(keyValue, valueValue);

Below is an example of JSON serialized with type info that’s causing the throw.

{"__type":"System.Collections.Generic.KeyValuePair`2[[System.String, System.Private.CoreLib],[System.String, System.Private.CoreLib]], System.Private.CoreLib","Key":"Yes","Value":"Yes"}

mythz · November 19, 2020, 4:43pm

Resolved in this commit, this change is available from latest v5.10.3+ that’s now on MyGet.

FYI the JSON.parse() JS Util is generally better suited for parsing adhoc JSON as you don’t need to specify the Type and it preserves the type of the JSON instead of coercing values into a string.

grexican · November 19, 2020, 4:59pm

Awesome, thanks.

FWIW I’m parsing adhoc (polymorphic) JSON that, deep down, has a KVP property in it, which is what’s causing the problem.

Is there a way to say “turn on __type for certain types but not others” ?

mythz · November 19, 2020, 5:33pm

No, although my recommendation would instead be focusing on removing reliance on it.