Allow properties to be nullable

[bjarnef]

Currently when using numeric or decimal properties ModelsBuilder generate these as int og decimal, but there doesn't seem to be a way to defined it as nullable, although the property in backoffice is allowed to be empty.

Maybe the properties should have a setting "Allow empty" or similar, which will generate to properties as int? and decimal? instead and it would be easier to handle a fallback value yourself as 0 sometimes is a valid value, but can be confusing if some properties are empty while others have the value 0.

It can of course use textstring instead string, but then one will not get the benefits of the numeric input. An alternative is to use textstring + regex on the property in backoffice to ensure a numeric value, but the generates type is still string.

It seems the be the same for textstring which always is generates as string and not string?.

Something like this would be great :)

[bergmania]

One could argue if a field is not mandatory, it should be nullable?

Thereby we do not need a new setting.

Overall I like the idea about making ModelsBuilder Nullable aware.

[bjarnef]

Possible, but not sure if there are use-cases where a property is not mandatory, but one want it not to nullable in code... but then the business logic in code can fallback to a default value.

I guess using the exiting mandatory setting would be a breaking change, but a new setting may not require a breaking change?

Sometimes we also change the mandatory setting later, but if the nullable property is based on this I guess it may require some code changes when generating models. Mostly we use SourceCodeManual mode, so not sure how it would affect the other ModelsBuilder modes.

[bergmania]

Changing doctype configuration will almost always require some code changes?

Code wise, It just seems weird if a property do not allow to be empty, but is not mandatory?
For reference-types is default value would then be null.

[bjarnef]

Yes, I guess it makes sense.. just until now validation hasn't effected models generations.

For now it is also possible a property is not mandatory, but the e.g. a numeric or decimal property has 0 as default value for int / decimal, which sometimes could be an issue when 0 is a valid value, e.g. it may be hard to tell if a product is actually free or the product just hasn't assigned a price, where one may want to hide the "add to basket" button and quantity field on product page. A solution here is to use textbox instead, a custom property editor or an additional property or rules to decide whether the product is free or just hasn't a price.

[JasonElkin]

I'm here for this!

Value types are straightforward, and IMO the default approach, where an empty field can return 0 is misleading - in situations described exactly as above.

I have written a package to try and address this: https://github.com/JasonElkin/Emptiness

I would love it if this was how Umbraco behaved OoTB.

WRT determining if reference types are nullable, I'm not sure a toggle in the back office is the best approach.There are packages, for example Contentment, where the nullability of the property depends on more complex configuration.

[abjerner]

I will make the argument that maybe this should be controlled at the data type level instead of at the property level. Eg. a value converter could have a fallback value if the property doesn't have a value.

The benefit of this will be that the developer of the property editor is still in control - eg. via the value converter. Downside will be if the property editor developer doesn't handle this scenario.

Ideally all Umbraco property editors (or at least those that make sense) should have a Nullable option on the data type. I know this creates some extra work handling it on the data type level, but like mentioned, I think it gives some more control.

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For instance, this is how I've handled it for my custom textbox property editor:

If I configure a fallback value in the data type, the value is never null. If I don't configure a fallback and don't enable the Nullable option, I get string.Empty, where as with the Nullable option enabled, I get null.

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Regarding ModelsBuilder, there currently isn't a good way for a value converter to indicate whether a refence type is nullable, as string? is essentially the same as string, but with an extra flag. System.Type doesn't support this flag.

I think the solution could be to create a NullableType class that extends System.Type, and then has an IsNullable property. If this is the case, ModelsBuilder could call the GetPropertyValueType method on the value converter, and then check whether the returned type is an instance of NullableType. Or perhaps the name of the class should be future proofed for additional settings, so maybe ModelsBuilderType or UmbracoType instead.

This is something I've discussed with a few members of the community already - eg. for adding this to my custom Models Builder package. But I haven't had the time to investigate this further. And it would probably be best if this type exists in Umbraco.