From a48d2bd967122e1c29d6891fad0543e76c348a08 Mon Sep 17 00:00:00 2001
From: Simon Boudrias <admin@simonboudrias.com>
Date: Sun, 14 Jul 2024 12:43:52 -0400
Subject: [PATCH] Feat(@inquirer/type): Add new utility types to @inquirer/type
 + vitest type tests

---
 packages/prompts/prompts.test.mts | 21 ++++-------
 packages/type/src/index.mts       | 58 ++-----------------------------
 packages/type/src/inquirer.mts    | 23 ++++++++++++
 packages/type/src/utils.mts       | 25 +++++++++++++
 packages/type/type.test.mts       | 28 +++++++++++++++
 5 files changed, 85 insertions(+), 70 deletions(-)
 create mode 100644 packages/type/src/inquirer.mts
 create mode 100644 packages/type/src/utils.mts
 create mode 100644 packages/type/type.test.mts

diff --git a/packages/prompts/prompts.test.mts b/packages/prompts/prompts.test.mts
index 3c0c723ff..ab08e18ef 100644
--- a/packages/prompts/prompts.test.mts
+++ b/packages/prompts/prompts.test.mts
@@ -1,5 +1,4 @@
-import { describe, it, expect } from 'vitest';
-import { Expect, Equal } from '@inquirer/type';
+import { describe, it, expect, expectTypeOf } from 'vitest';
 import {
   checkbox,
   confirm,
@@ -24,16 +23,10 @@ describe('@inquirer/prompts', () => {
     expect(select).toBeTypeOf('function');
     expect(Separator).toBeTypeOf('function');
   });
-});
 
-/**
- * Type assertions to validate the interfaces.
- */
-export interface Test {
-  1: Expect<
-    Equal<
-      NonNullable<Parameters<typeof checkbox>[0]['theme']>['helpMode'],
-      NonNullable<Parameters<typeof select>[0]['theme']>['helpMode']
-    >
-  >;
-}
+  it('checkbox and select have matching helpMode', () => {
+    expectTypeOf<
+      NonNullable<Parameters<typeof checkbox>[0]['theme']>['helpMode']
+    >().toEqualTypeOf<NonNullable<Parameters<typeof select>[0]['theme']>['helpMode']>();
+  });
+});
diff --git a/packages/type/src/index.mts b/packages/type/src/index.mts
index 6efeaa6e3..746fd1ca2 100644
--- a/packages/type/src/index.mts
+++ b/packages/type/src/index.mts
@@ -1,56 +1,2 @@
-import * as readline from 'node:readline';
-import MuteStream from 'mute-stream';
-
-export type InquirerReadline = readline.ReadLine & {
-  output: MuteStream;
-  input: NodeJS.ReadableStream;
-  clearLine: (dir: 0 | 1 | -1) => void; // https://nodejs.org/api/readline.html#rlclearlinedir
-};
-
-export class CancelablePromise<T> extends Promise<T> {
-  public cancel: () => void = () => {};
-}
-
-export type Prettify<T> = {
-  [K in keyof T]: T[K];
-  // eslint-disable-next-line @typescript-eslint/ban-types
-} & {};
-
-export type PartialDeep<T> = T extends object
-  ? {
-      [P in keyof T]?: PartialDeep<T[P]>;
-    }
-  : T;
-
-export type Context = {
-  input?: NodeJS.ReadableStream;
-  output?: NodeJS.WritableStream;
-  clearPromptOnDone?: boolean;
-};
-
-export type Prompt<Value, Config> = (
-  config: Config,
-  context?: Context,
-) => CancelablePromise<Value>;
-
-/**
- * Utility types used for writing tests
- *
- * Equal<A, B> checks that A and B are the same type, and returns
- * either `true` or `false`.
- *
- * You can use it in combination with `Expect` to write type
- * inference unit tests:
- *
- * ```ts
- * type t = Expect<
- *   Equal<Partial<{ a: string }>, { a?: string }>
- * >
- * ```
- */
-export type Equal<X, Y> =
-  (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y ? 1 : 2 ? true : false;
-
-export type Expect<T extends true> = T;
-
-export type Not<T extends boolean> = T extends true ? false : true;
+export * from './inquirer.mjs';
+export * from './utils.mjs';
diff --git a/packages/type/src/inquirer.mts b/packages/type/src/inquirer.mts
new file mode 100644
index 000000000..8e8bb6084
--- /dev/null
+++ b/packages/type/src/inquirer.mts
@@ -0,0 +1,23 @@
+import * as readline from 'node:readline';
+import MuteStream from 'mute-stream';
+
+export class CancelablePromise<T> extends Promise<T> {
+  public cancel: () => void = () => {};
+}
+
+export type InquirerReadline = readline.ReadLine & {
+  output: MuteStream;
+  input: NodeJS.ReadableStream;
+  clearLine: (dir: 0 | 1 | -1) => void; // https://nodejs.org/api/readline.html#rlclearlinedir
+};
+
+export type Context = {
+  input?: NodeJS.ReadableStream;
+  output?: NodeJS.WritableStream;
+  clearPromptOnDone?: boolean;
+};
+
+export type Prompt<Value, Config> = (
+  config: Config,
+  context?: Context,
+) => CancelablePromise<Value>;
diff --git a/packages/type/src/utils.mts b/packages/type/src/utils.mts
new file mode 100644
index 000000000..1264da494
--- /dev/null
+++ b/packages/type/src/utils.mts
@@ -0,0 +1,25 @@
+/* eslint-disable @typescript-eslint/ban-types */
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+export type Prettify<T> = {
+  [K in keyof T]: T[K];
+} & {};
+
+export type PartialDeep<T> = T extends object
+  ? {
+      [P in keyof T]?: PartialDeep<T[P]>;
+    }
+  : T;
+
+export type LiteralUnion<T extends F, F = string> = T | (F & {});
+export type KeyUnion<T> = LiteralUnion<Extract<keyof T, string>>;
+
+export type DistributiveMerge<A, B> = A extends any
+  ? Prettify<Omit<A, keyof B> & B>
+  : never;
+
+export type UnionToIntersection<T> = (
+  T extends any ? (input: T) => void : never
+) extends (input: infer Intersection) => void
+  ? Intersection
+  : never;
diff --git a/packages/type/type.test.mts b/packages/type/type.test.mts
new file mode 100644
index 000000000..a67a455dc
--- /dev/null
+++ b/packages/type/type.test.mts
@@ -0,0 +1,28 @@
+import { test, expectTypeOf } from 'vitest';
+import type {
+  DistributiveMerge,
+  PartialDeep,
+  UnionToIntersection,
+} from './src/index.mjs';
+
+test('DistributiveMerge', () => {
+  expectTypeOf<
+    DistributiveMerge<{ a: string; b: string }, { b: number }>
+  >().toEqualTypeOf<{
+    a: string;
+    b: number;
+  }>();
+});
+
+test('PartialDeep', () => {
+  expectTypeOf<PartialDeep<{ a: string }>>().toEqualTypeOf<{ a?: string }>();
+  expectTypeOf<PartialDeep<{ a: { b: string } }>>().toEqualTypeOf<{
+    a?: { b?: string };
+  }>();
+});
+
+test('UnionToIntersection', () => {
+  expectTypeOf<UnionToIntersection<{ x: string } | { y: number }>>().toEqualTypeOf<
+    { x: string } & { y: number }
+  >();
+});