Inconsistent undefined vs. null handling

Optional values for

• return values and
• property values

are correctly configurable with the TypeScriptGeneratorSettings.NullHandling setting.

Parameter values, however, are always optional with null, never with undefined.

There is no deeper reason for this, is there?

[simeyla]

Seems the default value of Undefined is troublesome with strict mode.

I think the default should be made to be string | null for a string field.

You get this typescript generated with the default of Undefined: (I think this is still the default?)

export interface Address {
    firstName: string | undefined;
    lastName: string | undefined;

This is for this C# class:

public class Person
{
    [JsonProperty(Required = Required.AllowNull)]
    public string FirstName { get; set; }

    [JsonProperty(Required = Required.AllowNull)]
    public string LastName { get; set; }
}

The problem is that with strict mode you cannot assign null to string | undefined. I also don’t want to use ?, and JSON.stringify() doesn’t serialized fields with undefined assigned to them.

So I think the default should be null for sure.

---

I managed to switch to using nullValue: 'Null' in my nswag file, and that now gives me the correct type. So I’m fine with this, just suggesting changing the default.

“codeGenerators”: { “swaggerToTypeScriptClient”: { “className”: “{controller}Client”, “moduleName”: “API”, “namespace”: “”, “typeScriptVersion”: 2.7, “template”: “Angular”, “promiseType”: “Promise”, “httpClass”: “HttpClient”, “useSingletonProvider”: true, “injectionTokenType”: “InjectionToken”, “rxJsVersion”: 6.0, “dateTimeType”: “MomentJS”, “nullValue”: “Null”,

I have wondered if having a third option of Null | Undefined would make any sense?, but I can do that with Partial<Address> if I need to (which I may do if I use the generated entities elsewhere).

eg. You can do this, and create sub-models and always be sure the names match the generated code.:

 type UIAddress = Partial<Address>;
 type CityStateZip = Pick<Address, 'city' | 'state' | 'zip'>;

Typescript is amazing!

[jeremyVignelles]

@simeyla : I don’t think NSwag is impacted because it doesn’t create object litterals, but instead serializes the function parameter.