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std/testing/types.ts

Deno standard library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// Copyright @dsherret and dsherret/conditional-type-checks contributors. All rights reserved. MIT license.
/** * Asserts at compile time that the provided type argument's type resolves to the expected boolean literal type. * @param expectTrue - True if the passed in type argument resolved to true. * @example * ```typescript, ignore * import { assertType, IsExact, IsNullable } from "https://deno.land/std@$STD_VERSION/testing/types.ts"; * * const result = "some result" as string | number; * * // compile error if the type of `result` is not exactly `string | number` * assertType<IsExact<typeof result, string | number>>(true); * * // causes a compile error that `true` is not assignable to `false` * assertType<IsNullable<string>>(true); // error: string is not nullable * ``` */export function assertType<T extends true | false>(_expectTrue: T) {}
/** * Asserts at compile time that the provided type argument's type resolves to true. * * @example * ```typescript * import { AssertTrue, Has, IsNullable } from "https://deno.land/std@$STD_VERSION/testing/types.ts"; * * const result = 1 as string | number | null; * * type doTest = AssertTrue<Has<typeof result, string> | IsNullable<typeof result>>; * ``` */export type AssertTrue<T extends true> = never;
/** * Asserts at compile time that the provided type argument's type resolves to false. * @example * ```typescript * import { AssertFalse, IsNever } from "https://deno.land/std@$STD_VERSION/testing/types.ts"; * * const result = 1 as string | number | null; * * type doTest = AssertFalse<IsNever<typeof result>>; * ``` */export type AssertFalse<T extends false> = never;
/** * Asserts at compile time that the provided type argument's type resolves to the expected boolean literal type. * @example * ```typescript * import { Assert, Has } from "https://deno.land/std@$STD_VERSION/testing/types.ts"; * * const result = 1 as string | number | null; * * type doTest = Assert<Has<typeof result, number>, true>; * ``` */export type Assert<T extends true | false, Expected extends T> = never;
/** * Checks if type `T` has the specified type `U`. */export type Has<T, U> = IsAny<T> extends true ? true : IsAny<U> extends true ? false : Extract<T, U> extends never ? false : true;
/** * Checks if type `T` does not have the specified type `U`. */export type NotHas<T, U> = Has<T, U> extends false ? true : false;
/** * Checks if type `T` is possibly null or undefined. */export type IsNullable<T> = Extract<T, null | undefined> extends never ? false : true;
/** * Checks if type `T` exactly matches type `U`. */export type IsExact<T, U> = TupleMatches<AnyToBrand<T>, AnyToBrand<U>> extends true ? TupleMatches<DeepPrepareIsExact<T>, DeepPrepareIsExact<U>> extends true ? true : false : false;
type DeepPrepareIsExact<T, VisitedTypes = never> = { // make optional properties required [P in keyof T]-?: IsAny<T[P]> extends true ? AnyBrand : DeepPrepareIsExactProp<T[P], T, VisitedTypes>;};
type DeepPrepareIsExactProp<Prop, Parent, VisitedTypes> = Prop extends VisitedTypes // recursive, bail ? Prop // not recursive, keep going and add the parent type as a visited type : DeepPrepareIsExact<Prop, VisitedTypes | Parent>;
/** * Checks if type `T` is the `any` type. */// https://stackoverflow.com/a/49928360/3406963export type IsAny<T> = 0 extends (1 & T) ? true : false;
/** * Checks if type `T` is the `never` type. */export type IsNever<T> = [T] extends [never] ? true : false;
/** * Checks if type `T` is the `unknown` type. */export type IsUnknown<T> = unknown extends T ? ([T] extends [null] ? false : true) : false;
type TupleMatches<T, U> = Matches<[T], [U]>;type Matches<T, U> = T extends U ? U extends T ? true : false : false;
type AnyToBrand<T> = IsAny<T> extends true ? AnyBrand : T;type AnyBrand = { __conditionalTypeChecksAny__: undefined };