From ec80b9f0ab2e2a92e4b17b6c267f56d4c6987626 Mon Sep 17 00:00:00 2001
From: Ian McIntosh <cranston.ian@gmail.com>
Date: Fri, 14 Jan 2022 11:42:30 -0500
Subject: [PATCH] Add [Either,Option].orNull. Closes #86.

---
 lib/src/either.dart   | 1 +
 lib/src/option.dart   | 1 +
 test/either_test.dart | 5 +++++
 test/option_test.dart | 5 +++++
 4 files changed, 12 insertions(+)

diff --git a/lib/src/either.dart b/lib/src/either.dart
index 2ee5b58..fa835ce 100644
--- a/lib/src/either.dart
+++ b/lib/src/either.dart
@@ -9,6 +9,7 @@ abstract class Either<L, R> implements TraversableMonadOps<Either<L, dynamic>, R
 
   Either<L, R> orElse(Either<L, R> other()) => fold((_) => other(), (_) => this);
   R getOrElse(R dflt()) => fold((_) => dflt(), id);
+  R? get orNull => fold((_) => null, id);
   R operator |(R dflt) => getOrElse(() => dflt);
   Either<L2, R> leftMap<L2>(L2 f(L l)) => fold((L l) => left(f(l)), right);
   Option<R> toOption() => fold((_) => none(), some);
diff --git a/lib/src/option.dart b/lib/src/option.dart
index 6cfdab9..dc4078f 100644
--- a/lib/src/option.dart
+++ b/lib/src/option.dart
@@ -10,6 +10,7 @@ abstract class Option<A> implements TraversableMonadPlusOps<Option, A> {
   B cata<B, B2 extends B>(B ifNone(), B2 ifSome(A a)) => fold(ifNone, ifSome);
   Option<A> orElse(Option<A> other()) => fold(other, (_) => this);
   A getOrElse(A dflt()) => fold(dflt, (a) => a);
+  A? get orNull => fold(() => null, id);
   Either<B, A> toEither<B>(B ifNone()) => fold(() => left(ifNone()), (a) => right(a));
   Either<dynamic, A> operator %(ifNone) => toEither(() => ifNone);
   A operator |(A dflt) => getOrElse(() => dflt);
diff --git a/test/either_test.dart b/test/either_test.dart
index 6461710..63b83e8 100644
--- a/test/either_test.dart
+++ b/test/either_test.dart
@@ -71,6 +71,11 @@ void main() {
     expect(r.ensure((x) => x < 0, () => 0), right(0));
   });
 
+  test('getOrElseNull', () {
+    expect(left<String, int>('error').orNull, isNull);
+    expect(right<String, int>(42).orNull, 42);
+  });
+
   group("EitherM", () => checkMonadLaws(EitherM));
 
   //group("EitherTMonad+Id", () => checkMonadLaws(eitherTMonad(IdM)));
diff --git a/test/option_test.dart b/test/option_test.dart
index 915e294..4ea0468 100644
--- a/test/option_test.dart
+++ b/test/option_test.dart
@@ -41,6 +41,11 @@ void main() {
     expect(Option.unless(true, 42), none());
   });
 
+  test('orNull', () {
+    expect(none().orNull, isNull);
+    expect(some(42).orNull, 42);
+  });
+
   group("OptionM", () => checkMonadLaws(new OptionMonadPlus()));
 
   //group("OptionTMonad+Id", () => checkMonadLaws(optionTMonad(IdM)));