115 lines
3.8 KiB
Plaintext
115 lines
3.8 KiB
Plaintext
import type {JsonPrimitive, JsonValue} from './basic';
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import type {EmptyObject} from './empty-object';
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import type {IsAny, UndefinedToOptional} from './internal';
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import type {NegativeInfinity, PositiveInfinity} from './numeric';
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import type {TypedArray} from './typed-array';
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// Note: The return value has to be `any` and not `unknown` so it can match `void`.
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type NotJsonable = ((...arguments_: any[]) => any) | undefined | symbol;
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type JsonifyTuple<T extends [unknown, ...unknown[]]> = {
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[Key in keyof T]: T[Key] extends NotJsonable ? null : Jsonify<T[Key]>;
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};
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type FilterJsonableKeys<T extends object> = {
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[Key in keyof T]: T[Key] extends NotJsonable ? never : Key;
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}[keyof T];
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/**
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JSON serialize objects (not including arrays) and classes.
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*/
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type JsonifyObject<T extends object> = {
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[Key in keyof Pick<T, FilterJsonableKeys<T>>]: Jsonify<T[Key]>;
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};
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/**
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Transform a type to one that is assignable to the `JsonValue` type.
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This includes:
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1. Transforming JSON `interface` to a `type` that is assignable to `JsonValue`.
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2. Transforming non-JSON value that is *jsonable* to a type that is assignable to `JsonValue`, where *jsonable* means the non-JSON value implements the `.toJSON()` method that returns a value that is assignable to `JsonValue`.
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@remarks
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An interface cannot be structurally compared to `JsonValue` because an interface can be re-opened to add properties that may not be satisfy `JsonValue`.
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@example
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```
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import type {Jsonify, JsonValue} from 'type-fest';
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interface Geometry {
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type: 'Point' | 'Polygon';
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coordinates: [number, number];
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}
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const point: Geometry = {
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type: 'Point',
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coordinates: [1, 1]
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};
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const problemFn = (data: JsonValue) => {
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// Does something with data
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};
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problemFn(point); // Error: type Geometry is not assignable to parameter of type JsonValue because it is an interface
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const fixedFn = <T>(data: Jsonify<T>) => {
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// Does something with data
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};
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fixedFn(point); // Good: point is assignable. Jsonify<T> transforms Geometry into value assignable to JsonValue
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fixedFn(new Date()); // Error: As expected, Date is not assignable. Jsonify<T> cannot transforms Date into value assignable to JsonValue
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```
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Non-JSON values such as `Date` implement `.toJSON()`, so they can be transformed to a value assignable to `JsonValue`:
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@example
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```
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import type {Jsonify} from 'type-fest';
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const time = {
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timeValue: new Date()
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};
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// `Jsonify<typeof time>` is equivalent to `{timeValue: string}`
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const timeJson = JSON.parse(JSON.stringify(time)) as Jsonify<typeof time>;
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```
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@link https://github.com/Microsoft/TypeScript/issues/1897#issuecomment-710744173
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@category JSON
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*/
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export type Jsonify<T> = IsAny<T> extends true
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? any
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: T extends PositiveInfinity | NegativeInfinity
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? null
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: T extends JsonPrimitive
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? T
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: // Instanced primitives are objects
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T extends Number
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? number
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: T extends String
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? string
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: T extends Boolean
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? boolean
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: T extends Map<any, any> | Set<any>
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? EmptyObject
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: T extends TypedArray
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? Record<string, number>
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: T extends NotJsonable
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? never // Non-JSONable type union was found not empty
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: // Any object with toJSON is special case
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T extends {toJSON(): infer J}
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? (() => J) extends () => JsonValue // Is J assignable to JsonValue?
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? J // Then T is Jsonable and its Jsonable value is J
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: Jsonify<J> // Maybe if we look a level deeper we'll find a JsonValue
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: T extends []
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? []
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: T extends [unknown, ...unknown[]]
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? JsonifyTuple<T>
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: T extends ReadonlyArray<infer U>
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? Array<U extends NotJsonable ? null : Jsonify<U>>
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: T extends object
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? JsonifyObject<UndefinedToOptional<T>> // JsonifyObject recursive call for its children
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: never; // Otherwise any other non-object is removed
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