How to define a Nullable Enum property?

[KBroichhausen]

Hey everyone,
given something like

export enum BarEnum {
	Bar1 = "bar1",
	Bar2 = "bar2"
}

export class Foo {
	@Required(true, null)
	@Enum(BarEnum)
	public bar: BarEnum | null;
}

I get the following part in the swagger,json

  "Foo": { "type": "object", "properties": { "bar": { "type": "string", "enum": ["bar1", "bar2"], "nullable": true, "minLength": 1 } }, "required": ["bar"] }

but if I actually use this model with a null value for bar as a post parameter in a controller I get a PARAM_VALIDATION_ERROR for this value with [...] must be equal to one of the allowed values. Given value: null\n'.

I don't really see the reason why. A workaround is to use something like

export class Foo {
	@Required(true, null)
	@Enum(BarEnum, null)
	public bar: BarEnum | null;
}

but that adds null as value in the enum section of the schema which is bad because I use a code generator and this adds "null" (so basically null as a string) as a possible value for the enum.

[NachtRitter]

You can try to use Any decorator from @tsed/schema package like this

export enum BarEnum {
	Bar1 = "bar1",
	Bar2 = "bar2"
}

export class Foo {
	@Enum(BarEnum)
        @Any('string', 'null')
	public bar: BarEnum | null;
}

[KBroichhausen]

I tried it without success. Still get the same error PARAM_VALIDATION_ERROR.

[Romakita]

I suggest you to create repository code example please ;)

[KBroichhausen]

Ok, quickly created a default project with the cli, slightly modified and removed some unecessary stuff. https://github.com/KBroichhausen/nullable-enum
Should just be npm install and npm run test. Relevant code is in HelloWorldController.ts and the test file for it.
Test is failing because of null but works as soon as you activate the // @Enum(BarEnum, null) line (but I don't want to have null being part of the enum itself)

[Romakita]

Hello @KBroichhausen
I tried that:

	@Required()
	@Allow(null)
	@Enum(BarEnum)

The json-schema is correctly generated, but the problem isn't related to Ts.ED.

{
  "type": "object",
  "properties": {
    "bar": {
      "type": ["null", "string"],
      "enum": ["bar1", "bar2"], // and ["bar1", "bar2", null]
    }
  },
  "required": ["bar"]
}

AJV doesn't seems to support this kind of rules (ajv-validator/ajv#824). I don't be able to fix that until ajv doesn't support correctly null value for an enum value.

I suggest you to add a default enum value like this:

export enum BarEnum {
	Bar1 = "bar1",
	Bar2 = "bar2",
	UNKNOWN = "UNKNOWN"
}

export class Foo {
	@Enum(BarEnum)
        @Default(BarEnum.UNKNOWN)
	public bar: BarEnum  = BarEnum.UNKNOWN;
}

See you
Romain

[KBroichhausen]

Oh, OK, Thank you very much.
Most of the times if something wasn't working, I just had to dig deeper in the documentation. Didn't know this is really kind of an unsupported feature/bug.
To add a little bit more, partially unrequired, context: I use a code generator to create an angular library from the schema, then I use the enums to create options for a selector box (combined with a translation file). Eventually, it doesn't make much difference to use your suggestion with the default unknown value or use @Enum(BarEnum, null) which adds the null value to the schema and code generated enum => in both cases I had to filter that value out for the selector in the frontend.
As I have many more enums, I stick with the null value, so I don't have to deal with it on the backend. But I consider this more as a workaround, that's why I asked here for a proper solution.

[Romakita]

Yes I understand your point, it's consistent. I'm sorry to not have a real solution for the null value + enum. I just discovered this limitation and in fact, I never tried that have a null value on Enums before ;)

See you