From bb6c889127063e8e9eaa6d5808b4bd2fa38cbe92 Mon Sep 17 00:00:00 2001
From: Aura <kyradiscord@gmail.com>
Date: Sat, 2 Nov 2024 14:38:57 +0100
Subject: [PATCH] feat(Option): add `isNoneOr` (#824)

---
 packages/result/src/lib/Option.ts    | 27 +++++++++++++++++++++++++
 packages/result/tests/Option.test.ts | 30 ++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/packages/result/src/lib/Option.ts b/packages/result/src/lib/Option.ts
index 11528c497b..d92e3fbed5 100644
--- a/packages/result/src/lib/Option.ts
+++ b/packages/result/src/lib/Option.ts
@@ -88,6 +88,33 @@ export class Option<T, Exists extends boolean = boolean> {
 		return !this[ExistsProperty];
 	}
 
+	/**
+	 * Returns `true` if the option is a `None` value or the value inside of it matches a predicate.
+	 *
+	 * @example
+	 * ```typescript
+	 * const x: Option<number> = some(2);
+	 * assert.equal(x.isNoneOr((x) => x > 1), true);
+	 * ```
+	 * @example
+	 * ```typescript
+	 * const x: Option<number> = some(0);
+	 * assert.equal(x.isNoneOr((x) => x > 1), false);
+	 * ```
+	 * @example
+	 * ```typescript
+	 * const x: Option<number> = none;
+	 * assert.equal(x.isNoneOr((x) => x > 1), true);
+	 * ```
+	 *
+	 * @see {@link https://doc.rust-lang.org/std/option/enum.Option.html#method.is_none_or}
+	 */
+	public isNoneOr<R extends T>(cb: (value: T) => value is R): this is None | Some<R>;
+	public isNoneOr<R extends boolean>(cb: (value: T) => R): If<Exists, R, true>;
+	public isNoneOr<R extends boolean>(cb: (value: T) => R): If<Exists, R, true> {
+		return this.match({ some: (value) => cb(value), none: () => true });
+	}
+
 	/**
 	 * Returns the contained `Some` value.
 	 * @param message The message for the error.
diff --git a/packages/result/tests/Option.test.ts b/packages/result/tests/Option.test.ts
index 8c8a2388d1..b1ac40f0ae 100644
--- a/packages/result/tests/Option.test.ts
+++ b/packages/result/tests/Option.test.ts
@@ -58,6 +58,36 @@ describe('Option', () => {
 			});
 		});
 
+		describe('isNoneOr', () => {
+			test('GIVEN some AND true-returning callback THEN returns true', () => {
+				const x = some(2);
+				const cb = vi.fn((value: number) => value > 1);
+
+				expect(x.isNoneOr(cb)).toBe(true);
+				expect(cb).toHaveBeenCalledTimes(1);
+				expect(cb).toHaveBeenCalledWith(2);
+				expect(cb).toHaveLastReturnedWith(true);
+			});
+
+			test('GIVEN some AND false-returning callback THEN returns false', () => {
+				const x = some(0);
+				const cb = vi.fn((value: number) => value > 1);
+
+				expect(x.isNoneOr(cb)).toBe(false);
+				expect(cb).toHaveBeenCalledTimes(1);
+				expect(cb).toHaveBeenCalledWith(0);
+				expect(cb).toHaveLastReturnedWith(false);
+			});
+
+			test('GIVEN none THEN always returns false', () => {
+				const x = none;
+				const cb = vi.fn((value: number) => value > 1);
+
+				expect(x.isNoneOr(cb)).toBe(true);
+				expect(cb).not.toHaveBeenCalled();
+			});
+		});
+
 		describe('expect', () => {
 			test('GIVEN ok THEN returns value', () => {
 				const x = some(2);