lib/types/jtd-schema.ts
/** numeric strings */
type NumberType = "float32" | "float64" | "int8" | "uint8" | "int16" | "uint16" | "int32" | "uint32"
/** string strings */
type StringType = "string" | "timestamp"
/** Generic JTD Schema without inference of the represented type */
export type SomeJTDSchemaType = (
| // ref
{ref: string}
// primitives
| {type: NumberType | StringType | "boolean"}
// enum
| {enum: string[]}
// elements
| {elements: SomeJTDSchemaType}
// values
| {values: SomeJTDSchemaType}
// properties
| {
properties: Record<string, SomeJTDSchemaType>
optionalProperties?: Record<string, SomeJTDSchemaType>
additionalProperties?: boolean
}
| {
properties?: Record<string, SomeJTDSchemaType>
optionalProperties: Record<string, SomeJTDSchemaType>
additionalProperties?: boolean
}
// discriminator
| {discriminator: string; mapping: Record<string, SomeJTDSchemaType>}
// empty
// NOTE see the end of
// https://github.com/typescript-eslint/typescript-eslint/issues/2063#issuecomment-675156492
// eslint-disable-next-line @typescript-eslint/ban-types
| {}
) & {
nullable?: boolean
metadata?: Record<string, unknown>
definitions?: Record<string, SomeJTDSchemaType>
}
/** required keys of an object, not undefined */
type RequiredKeys<T> = {
[K in keyof T]-?: undefined extends T[K] ? never : K
}[keyof T]
/** optional or undifined-able keys of an object */
type OptionalKeys<T> = {
[K in keyof T]-?: undefined extends T[K] ? K : never
}[keyof T]
/** type is true if T is a union type */
type IsUnion_<T, U extends T = T> = false extends (
T extends unknown ? ([U] extends [T] ? false : true) : never
)
? false
: true
type IsUnion<T> = IsUnion_<T>
/** type is true if T is identically E */
type TypeEquality<T, E> = [T] extends [E] ? ([E] extends [T] ? true : false) : false
/** type is true if T or null is identically E or null*/
type NullTypeEquality<T, E> = TypeEquality<T | null, E | null>
/** gets only the string literals of a type or null if a type isn't a string literal */
type EnumString<T> = [T] extends [never]
? null
: T extends string
? string extends T
? null
: T
: null
/** true if type is a union of string literals */
type IsEnum<T> = null extends EnumString<T> ? false : true
/** true only if all types are array types (not tuples) */
// NOTE relies on the fact that tuples don't have an index at 0.5, but arrays
// have an index at every number
type IsElements<T> = false extends IsUnion<T>
? [T] extends [readonly unknown[]]
? undefined extends T[0.5]
? false
: true
: false
: false
/** true if the the type is a values type */
type IsValues<T> = false extends IsUnion<T> ? TypeEquality<keyof T, string> : false
/** true if type is a properties type and Union is false, or type is a discriminator type and Union is true */
type IsRecord<T, Union extends boolean> = Union extends IsUnion<T>
? null extends EnumString<keyof T>
? false
: true
: false
/** true if type represents an empty record */
type IsEmptyRecord<T> = [T] extends [Record<string, never>]
? [T] extends [never]
? false
: true
: false
/** actual schema */
export type JTDSchemaType<T, D extends Record<string, unknown> = Record<string, never>> = (
| // refs - where null wasn't specified, must match exactly
(null extends EnumString<keyof D>
? never
:
| ({[K in keyof D]: [T] extends [D[K]] ? {ref: K} : never}[keyof D] & {nullable?: false})
// nulled refs - if ref is nullable and nullable is specified, then it can
// match either null or non-null definitions
| (null extends T
? {
[K in keyof D]: [Exclude<T, null>] extends [Exclude<D[K], null>]
? {ref: K}
: never
}[keyof D] & {nullable: true}
: never))
// empty - empty schemas also treat nullable differently in that it's now fully ignored
| (unknown extends T ? {nullable?: boolean} : never)
// all other types // numbers - only accepts the type number
| ((true extends NullTypeEquality<T, number>
? {type: NumberType}
: // booleans - accepts the type boolean
true extends NullTypeEquality<T, boolean>
? {type: "boolean"}
: // strings - only accepts the type string
true extends NullTypeEquality<T, string>
? {type: StringType}
: // strings - only accepts the type Date
true extends NullTypeEquality<T, Date>
? {type: "timestamp"}
: // enums - only accepts union of string literals
// TODO we can't actually check that everything in the union was specified
true extends IsEnum<Exclude<T, null>>
? {enum: EnumString<Exclude<T, null>>[]}
: // arrays - only accepts arrays, could be array of unions to be resolved later
true extends IsElements<Exclude<T, null>>
? T extends readonly (infer E)[]
? {
elements: JTDSchemaType<E, D>
}
: never
: // empty properties
true extends IsEmptyRecord<Exclude<T, null>>
?
| {properties: Record<string, never>; optionalProperties?: Record<string, never>}
| {optionalProperties: Record<string, never>}
: // values
true extends IsValues<Exclude<T, null>>
? T extends Record<string, infer V>
? {
values: JTDSchemaType<V, D>
}
: never
: // properties
true extends IsRecord<Exclude<T, null>, false>
? ([RequiredKeys<Exclude<T, null>>] extends [never]
? {
properties?: Record<string, never>
}
: {
properties: {[K in RequiredKeys<T>]: JTDSchemaType<T[K], D>}
}) &
([OptionalKeys<Exclude<T, null>>] extends [never]
? {
optionalProperties?: Record<string, never>
}
: {
optionalProperties: {
[K in OptionalKeys<T>]: JTDSchemaType<Exclude<T[K], undefined>, D>
}
}) & {
additionalProperties?: boolean
}
: // discriminator
true extends IsRecord<Exclude<T, null>, true>
? {
[K in keyof Exclude<T, null>]-?: Exclude<T, null>[K] extends string
? {
discriminator: K
mapping: {
// TODO currently allows descriminator to be present in schema
[M in Exclude<T, null>[K]]: JTDSchemaType<
Omit<T extends Record<K, M> ? T : never, K>,
D
>
}
}
: never
}[keyof Exclude<T, null>]
: never) &
(null extends T
? {
nullable: true
}
: {nullable?: false}))
) & {
// extra properties
metadata?: Record<string, unknown>
// TODO these should only be allowed at the top level
definitions?: {[K in keyof D]: JTDSchemaType<D[K], D>}
}
type JTDDataDef<S, D extends Record<string, unknown>> =
| // ref
(S extends {ref: string}
? D extends {[K in S["ref"]]: infer V}
? JTDDataDef<V, D>
: never
: // type
S extends {type: NumberType}
? number
: S extends {type: "boolean"}
? boolean
: S extends {type: "string"}
? string
: S extends {type: "timestamp"}
? string | Date
: // enum
S extends {enum: readonly (infer E)[]}
? string extends E
? never
: [E] extends [string]
? E
: never
: // elements
S extends {elements: infer E}
? JTDDataDef<E, D>[]
: // properties
S extends {
properties: Record<string, unknown>
optionalProperties?: Record<string, unknown>
additionalProperties?: boolean
}
? {-readonly [K in keyof S["properties"]]-?: JTDDataDef<S["properties"][K], D>} & {
-readonly [K in keyof S["optionalProperties"]]+?: JTDDataDef<
S["optionalProperties"][K],
D
>
} & ([S["additionalProperties"]] extends [true] ? Record<string, unknown> : unknown)
: S extends {
properties?: Record<string, unknown>
optionalProperties: Record<string, unknown>
additionalProperties?: boolean
}
? {-readonly [K in keyof S["properties"]]-?: JTDDataDef<S["properties"][K], D>} & {
-readonly [K in keyof S["optionalProperties"]]+?: JTDDataDef<
S["optionalProperties"][K],
D
>
} & ([S["additionalProperties"]] extends [true] ? Record<string, unknown> : unknown)
: // values
S extends {values: infer V}
? Record<string, JTDDataDef<V, D>>
: // discriminator
S extends {discriminator: infer M; mapping: Record<string, unknown>}
? [M] extends [string]
? {
[K in keyof S["mapping"]]: JTDDataDef<S["mapping"][K], D> & {[KM in M]: K}
}[keyof S["mapping"]]
: never
: // empty
unknown)
| (S extends {nullable: true} ? null : never)
export type JTDDataType<S> = S extends {definitions: Record<string, unknown>}
? JTDDataDef<S, S["definitions"]>
: JTDDataDef<S, Record<string, never>>