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128 lines
3.9 KiB
TypeScript
128 lines
3.9 KiB
TypeScript
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
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// Copyright @dsherret and dsherret/conditional-type-checks contributors. All rights reserved. MIT license.
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/**
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* Asserts at compile time that the provided type argument's type resolves to the expected boolean literal type.
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* @param expectTrue - True if the passed in type argument resolved to true.
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* @example
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* ```typescript, ignore
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* import { assertType, IsExact, IsNullable } from "https://deno.land/std@$STD_VERSION/testing/types.ts";
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*
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* const result = "some result" as string | number;
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*
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* // compile error if the type of `result` is not exactly `string | number`
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* assertType<IsExact<typeof result, string | number>>(true);
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*
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* // causes a compile error that `true` is not assignable to `false`
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* assertType<IsNullable<string>>(true); // error: string is not nullable
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* ```
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*/
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export function assertType<T extends true | false>(_expectTrue: T) {
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}
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/**
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* Asserts at compile time that the provided type argument's type resolves to true.
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*
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* @example
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* ```typescript
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* import { AssertTrue, Has, IsNullable } from "https://deno.land/std@$STD_VERSION/testing/types.ts";
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*
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* const result = 1 as string | number | null;
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*
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* type doTest = AssertTrue<Has<typeof result, string> | IsNullable<typeof result>>;
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* ```
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*/
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export type AssertTrue<T extends true> = never;
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/**
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* Asserts at compile time that the provided type argument's type resolves to false.
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* @example
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* ```typescript
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* import { AssertFalse, IsNever } from "https://deno.land/std@$STD_VERSION/testing/types.ts";
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*
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* const result = 1 as string | number | null;
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*
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* type doTest = AssertFalse<IsNever<typeof result>>;
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* ```
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*/
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export type AssertFalse<T extends false> = never;
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/**
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* Asserts at compile time that the provided type argument's type resolves to the expected boolean literal type.
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* @example
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* ```typescript
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* import { Assert, Has } from "https://deno.land/std@$STD_VERSION/testing/types.ts";
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*
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* const result = 1 as string | number | null;
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*
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* type doTest = Assert<Has<typeof result, number>, true>;
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* ```
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*/
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export type Assert<T extends true | false, Expected extends T> = never;
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/**
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* Checks if type `T` has the specified type `U`.
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*/
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export type Has<T, U> = IsAny<T> extends true ? true
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: IsAny<U> extends true ? false
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: Extract<T, U> extends never ? false
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: true;
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/**
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* Checks if type `T` does not have the specified type `U`.
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*/
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export type NotHas<T, U> = Has<T, U> extends false ? true : false;
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/**
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* Checks if type `T` is possibly null or undefined.
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*/
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export type IsNullable<T> = Extract<T, null | undefined> extends never ? false
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: true;
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/**
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* Checks if type `T` exactly matches type `U`.
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*/
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export type IsExact<T, U> = TupleMatches<AnyToBrand<T>, AnyToBrand<U>> extends
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true
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? TupleMatches<DeepPrepareIsExact<T>, DeepPrepareIsExact<U>> extends true
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? true
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: false
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: false;
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type DeepPrepareIsExact<T, VisitedTypes = never> = {
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// make optional properties required
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[P in keyof T]-?: IsAny<T[P]> extends true ? AnyBrand
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: DeepPrepareIsExactProp<T[P], T, VisitedTypes>;
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};
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type DeepPrepareIsExactProp<Prop, Parent, VisitedTypes> = Prop extends
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VisitedTypes
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// recursive, bail
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? Prop
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// not recursive, keep going and add the parent type as a visited type
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: DeepPrepareIsExact<Prop, VisitedTypes | Parent>;
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/**
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* Checks if type `T` is the `any` type.
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*/
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// https://stackoverflow.com/a/49928360/3406963
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export type IsAny<T> = 0 extends (1 & T) ? true : false;
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/**
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* Checks if type `T` is the `never` type.
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*/
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export type IsNever<T> = [T] extends [never] ? true : false;
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/**
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* Checks if type `T` is the `unknown` type.
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*/
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export type IsUnknown<T> = unknown extends T
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? ([T] extends [null] ? false : true)
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: false;
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type TupleMatches<T, U> = Matches<[T], [U]>;
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type Matches<T, U> = T extends U ? U extends T ? true : false : false;
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type AnyToBrand<T> = IsAny<T> extends true ? AnyBrand : T;
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type AnyBrand = { __conditionalTypeChecksAny__: undefined };
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