Enforce Constructor Call or Add Nullable Returns

[AeonSake]

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Is your feature request related to a problem? Please describe. Currently, the IDeserializer.Deserialize<T> methods return null if the parsed string is empty (or whitespaces). However, because the interface description declares the return type as T and not T? it is not immediately obvious that null can even be a valid return value.

Describe the solution you'd like I would like the deserializer to always enforce the type construction (optionally via a DeserializerBuilder option like WithEnforceConstructorCall() ?), or change the interface return type to T? to make it clear to the user, that null is a possibility.

Describe alternatives you've considered Override/ignore compiler info/warning and do a null-check on the returned instance regardless.

Additional context There may be built-in deserializer options I did not see and this might also be possible with custom type converters, object factories, etc. If that is the case, please let me know.

[EdwardCooke]

Can you not do something like this deserialize.Deserialize<SomeclassName?>(yamltext);

Or are you saying that you would just expect the interface to already have the nullable attribute by default? I think that could be a breaking change, albeit just compiler warnings but it would be annoying for existing consumers to suddenly need nullable checks or directives to get rid of them.

[AeonSake]

In my opinion, the interface should always fully inform the user about the type to expect. If null is a possibility, the interface should reflect that. Alternatively, an exception would also be ok I guess. But as it stands now, the interface tells the user that null is never a valid result, therefore also producing compiler warnings if you do a null-check regardless (depending on your settings). So either have the type always be reflected as T?, throw an exception, or make it a compiler setting to at least construct the empty object instead of returning the unexpected null. As I understand it, an empty string is technically valid YAML, but contains no valid documents. I would still like the interface to reflect that behavior.

Just for the sake of comparison, Newtonsoft.Json and System.Text.Json both have T? as the expected return type (though System.Text.Json also throws an exception since an empty string is technically not valid JSON).