From 0ec676d651af8bdf8be536588a17ddf19073f830 Mon Sep 17 00:00:00 2001
From: silverwind <me@silverwind.io>
Date: Thu, 8 Aug 2024 19:25:28 +0200
Subject: [PATCH] Add `EmptyArray` and `IsEmptyArray`

Fixes: https://github.com/sindresorhus/type-fest/issues/929
---
 index.d.ts              |  1 +
 source/empty-array.d.ts | 32 ++++++++++++++++++++++++++++++++
 test-d/empty-array.ts   | 28 ++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+)
 create mode 100644 source/empty-array.d.ts
 create mode 100644 test-d/empty-array.ts

diff --git a/index.d.ts b/index.d.ts
index 8c1588260..60e92332c 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -9,6 +9,7 @@ export type {KeysOfUnion} from './source/keys-of-union';
 export type {DistributedOmit} from './source/distributed-omit';
 export type {DistributedPick} from './source/distributed-pick';
 export type {EmptyObject, IsEmptyObject} from './source/empty-object';
+export type {EmptyArray, IsEmptyArray} from './source/empty-array';
 export type {IfEmptyObject} from './source/if-empty-object';
 export type {NonEmptyObject} from './source/non-empty-object';
 export type {UnknownRecord} from './source/unknown-record';
diff --git a/source/empty-array.d.ts b/source/empty-array.d.ts
new file mode 100644
index 000000000..2be962a47
--- /dev/null
+++ b/source/empty-array.d.ts
@@ -0,0 +1,32 @@
+/**
+Represents a strictly empty array, the `[]` value.
+
+@example
+```
+import type {EmptyArray} from 'type-fest';
+
+const bar1: EmptyArray = []; // Pass
+const bar2: EmptyArray = {}; // Fail
+const bar3: EmptyArray = null; // Fail
+```
+
+@category Array
+*/
+export type EmptyArray = never[];
+
+/**
+Returns a `boolean` for whether the type is strictly equal to an empty array, the `[]` value.
+
+@example
+```
+import type {IsEmptyArray} from 'type-fest';
+
+type Pass = IsEmptyArray<[]>; //=> true
+type Fail = IsEmptyArray<{}>; //=> false
+type Fail = IsEmptyArray<null>; //=> false
+```
+
+@see EmptyArray
+@category Array
+*/
+export type IsEmptyArray<T> = T extends EmptyArray ? true : false;
diff --git a/test-d/empty-array.ts b/test-d/empty-array.ts
new file mode 100644
index 000000000..ac660ab0d
--- /dev/null
+++ b/test-d/empty-array.ts
@@ -0,0 +1,28 @@
+import {expectAssignable, expectType} from 'tsd';
+import type {EmptyArray, IsEmptyArray} from '../index';
+
+declare let foo: EmptyArray;
+
+expectAssignable<never[]>(foo);
+expectAssignable<never[]>(foo = []);
+
+foo = [];
+foo = [...[]]; // eslint-disable-line unicorn/no-useless-spread
+foo = [...new Set([])];
+const _length = foo.length;
+
+// @ts-expect-error
+foo = [1];
+// @ts-expect-error
+foo = [...[1]]; // eslint-disable-line unicorn/no-useless-spread
+// @ts-expect-error
+foo = [...new Set([1])];
+// @ts-expect-error
+foo = null;
+// @ts-expect-error
+foo.bar = 42;
+// @ts-expect-error
+foo.bar = [];
+
+expectType<IsEmptyArray<[]>>(true);
+expectType<IsEmptyArray<typeof foo>>(true);