Add LiteralToPrimitiveDeep type (#584)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

Author: alvis

index.d.ts

@@ -55,6 +55,7 @@ export type {Jsonify} from './source/jsonify';
 export type {Jsonifiable} from './source/jsonifiable';
 export type {Schema} from './source/schema';
 export type {LiteralToPrimitive} from './source/literal-to-primitive';
+export type {LiteralToPrimitiveDeep} from './source/literal-to-primitive-deep';
 export type {
 PositiveInfinity,
 NegativeInfinity,

readme.md

@@ -157,6 +157,7 @@ Click the type names for complete docs.
 - [`ConditionalExcept`](source/conditional-except.d.ts) - Like `Omit` except it removes properties from a shape where the values extend the given `Condition` type.
 - [`UnionToIntersection`](source/union-to-intersection.d.ts) - Convert a union type to an intersection type.
 - [`LiteralToPrimitive`](source/literal-to-primitive.d.ts) - Convert a [literal type](https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#literal-types) to the [primitive type](source/primitive.d.ts) it belongs to.
+- [`LiteralToPrimitiveDeep`](source/literal-to-primitive-deep.d.ts) - Like `LiteralToPrimitive` except it converts literal types inside an object or array deeply.
 - [`Stringified`](source/stringified.d.ts) - Create a type with the keys of the given type changed to `string` type.
 - [`IterableElement`](source/iterable-element.d.ts) - Get the element type of an `Iterable`/`AsyncIterable`. For example, an array or a generator.
 - [`Entry`](source/entry.d.ts) - Create a type that represents the type of an entry of a collection.

source/literal-to-primitive-deep.d.ts

@@ -0,0 +1,36 @@
+import type {LiteralToPrimitive} from './literal-to-primitive';
+import type {OmitIndexSignature} from './omit-index-signature';
+
+/**
+Like `LiteralToPrimitive` except it converts literal types inside an object or array deeply.
+
+For example, given a constant object, it returns a new object type with the same keys but with all the values converted to primitives.
+
+@see LiteralToPrimitive
+
+Use-case: Deal with data that is imported from a JSON file.
+
+@example
+```
+import type {LiteralToPrimitiveDeep, TsConfigJson} from 'type-fest';
+import tsconfig from 'path/to/tsconfig.json';
+
+function doSomethingWithTSConfig(config: LiteralToPrimitiveDeep<TsConfigJson>) { ... }
+
+// No casting is needed to pass the type check
+doSomethingWithTSConfig(tsconfig);
+
+// If LiteralToPrimitiveDeep is not used, you need to cast the imported data like this:
+doSomethingWithTSConfig(tsconfig as TsConfigJson);
+```
+
+@category Type
+@category Object
+*/
+export type LiteralToPrimitiveDeep<T> = T extends object
+? T extends Array<infer U>
+? Array<LiteralToPrimitiveDeep<U>>
+: {
+[K in keyof OmitIndexSignature<T>]: LiteralToPrimitiveDeep<T[K]>;
+}
+: LiteralToPrimitive<T>;

test-d/literal-to-primitive-deep.ts

@@ -0,0 +1,54 @@
+import {expectType} from 'tsd';
+import type {IsEqual, LiteralToPrimitiveDeep} from '../index';
+
+type LiteralObject = {
+a: string;
+b: number;
+c: boolean;
+d: {
+e: bigint;
+f: symbol;
+g: {
+h: string[];
+i: {
+j: boolean;
+k: {
+l: 1;
+m: 'hello';
+o: [1, 2, 3];
+p: ['a', 'b', 'c'];
+q: [1, 'a', true];
+};
+};
+};
+};
+};
+
+type PrimitiveObject = {
+a: string;
+b: number;
+c: boolean;
+d: {
+e: bigint;
+f: symbol;
+g: {
+h: string[];
+i: {
+j: boolean;
+k: {
+l: number;
+m: string;
+o: number[];
+p: string[];
+q: Array<number | string | boolean>;
+};
+};
+};
+};
+};
+
+const typeEqual: IsEqual<
+LiteralToPrimitiveDeep<LiteralObject>,
+PrimitiveObject
+> = true;
+expectType<true>(typeEqual);