> But I haven't used source generators in C# in at least 10 years, and I honestly don't know why anyone would at this point.
A challenge with .NET web APIs is that it's not possible to detect when interacting with a payload deserialized from JSON whether it's `null` because it was set to `null` or `null` because it was not supplied.
A common way to work around this is to provide a `IsSet` boolean:
private bool _isNameSet;
public string? Name { get; set { ...; isNameSet = true; } }
Now you can check if the value is set.
However, you can see how tedious this can get without a source Generator. With a source generator, we simply take nullable partial properties and generate the stub automatically.
public partial string? Name { get; set; }
Now a single marker attribute will generate as many `Is*Set` properties as needed.
Of course, the other use case is for AOT to avoid reflection by generating the source at runtime.
That is tedious with or without a source generator, mainly because there's a much better way to do it:
public Optional<string> Name;
With Optional being something like:
class Optional<T> {
public T? Value;
public bool IsSet;
}
I'm actually partial to using IEnumerable for this, and I'd reverse the boolean:
class Optional<T> {
public IEnumerable<T> ValueOrEmpty;
public bool IsExplicitNull;
}
With this approach (either one) you can easily define Map (or "Select", if you choose LINQ verbiage) on Optional and go delete 80% of your "if" statements that are checking that boolean.
Why mess with source generators? They're just making it slightly easier to do this in a way that is really painful.
I'd strongly recommend that if you find yourself wanting Null to represent two different ideas, then you actually just want those two different ideas represented explicitly, e.g. with an Enum. Which you can still do with a basic wrapper like this. The user didn't say "Null", they said "Unknown" or "Not Applicable" or something. Record that.
public OneOf<string, NotApplicable> Name
A good OneOf implementation is here (I have nothing to do with this library, I just like it):
A common way to work around this is to provide a `IsSet` boolean:
Now you can check if the value is set.However, you can see how tedious this can get without a source Generator. With a source generator, we simply take nullable partial properties and generate the stub automatically.
Now a single marker attribute will generate as many `Is*Set` properties as needed.Of course, the other use case is for AOT to avoid reflection by generating the source at runtime.