Support generating typescript interfaces from an abstract sql model

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Change-type: minor

[thgreasi]

Afaik the nullable part should be [] | [T]. It seems that [T?] isn't exactly equivalent since changing the respective line in the SDK will cause the typings to error.
See: https://github.com/balena-io/balena-sdk/blob/b24371c390a65cdfabff2bb41404ed2b4ea1c841/typings/pinejs-client-core.d.ts#L17-L19

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I think that might be an issue in the SDK typings @thgreasi and how it does typing magic since [T?] vs [] | [T] should be equivalent and at least on a basic test using

const x: OptionalNavigationResource<Device> = [] as any;
if (Array.isArray(x)) {
	const y = x[0]
}

then y ends up with the same type with either [T?] or [] | [T]

[thgreasi]

Well strictly speaking [T?] means that there is a T or undefined in the single item tuple, while the other describes that it's either a single item T tuple or an empty array.

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T[0] will return undefined in both cases @thgreasi and check the following:

let x: [string?]
type l = typeof x.length
// type l = 0 | 1
type e = typeof x[0]
// type e = string | undefined

the typing seems to recognise it's length as 0 | 1 and the element is string | undefined, the same as for [] | [T]:

let x: [] | [string]
type l = typeof x.length
// type l = 0 | 1
type e = typeof x[0]
// type e = string | undefined

[thgreasi]

I have a type helper in the SDK which generated the "write" variant given the "read" one.
Imo it's more convenient that having to use two separate types.
See: https://github.com/balena-io/balena-sdk/blob/master/typings/pinejs-client-core.d.ts#L350-L352

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It's not possible to generate the "write" typings purely from the "read" typings, for instance Date | string is valid for write but the read typing is just string