JSON `null` support for optional swift types?

[ecito]

Optional properties don't accept null values

Issue

The @Schemable macro generates schemas for optional properties (Int?, String?, etc.) that accept missing fields but reject explicit null values.

@Schemable
struct User {
  let name: String
  let age: Int?
}

Works:

{"name": "Alice"}

Fails:

{"name": "Alice", "age": null}

Error: Type mismatch: the instance of type 'null' does not match the expected type 'integer'

Current Behavior

For let age: Int?, the macro generates:

JSONProperty(key: "age") {
  JSONInteger()  // Only accepts integers, rejects null
}
// Not required, so can be omitted

Expected Behavior

Optional properties should accept both the unwrapped type and null values, since many APIs explicitly send null for absent values.

Possible Solutions

1. .orNull() modifier - Add a new modifier and apply to optionals
2. OneOf composition - Wrap optional types in OneOf([type, null])
3. Type array - Use {"type": ["integer", "null"]} if supported

Which approach would you prefer? Happy to submit a PR.

[ajevans99]

Great catch.

For expansion behavior, I like something like .orNull(style: .type) for simple scalar types (string, integer, number, boolean) and falling back to .orNull(style: .union) for anything complex (object, array, $ref, unions, etc.). This makes the schema minimal while accurately expressing that Optional<T> fields may be omitted or explicitly set to null. I also like .type style for primitives since it tends to produce clearer validation errors.

A global SchemaOptions.optionalNulls flag could be nice for configuring this behavior, but it’s not critical right now.

[ecito]

implemented in #128

not sure if you mean SchemaOptions.optionalNulls as a global flag for a single type like @Schemable(optionalNulls: true), or a truly global style option that applies to all types? the latter would definitely be useful since these kind of options typically cover the whole json service's surface, but unsure if it's actually possible unfortunately =/ mainly because we can't have any runtime global variables available at compile time...

looking into using package traits to configure the macro.

[ecito]

here we go! ecito#1

(I had to get the library working with swift 6.1 first)

[ajevans99]

implemented in #128

not sure if you mean SchemaOptions.optionalNulls as a global flag for a single type like @Schemable(optionalNulls: true), or a truly global style option that applies to all types? the latter would definitely be useful since these kind of options typically cover the whole json service's surface, but unsure if it's actually possible unfortunately =/ mainly because we can't have any runtime global variables available at compile time...

looking into using package traits to configure the macro.

I meant the former for sure. You're implementation looks great

[ajevans99]

Closed by #128