Optional: add setOption

Author: gcanti

CHANGELOG.md

@@ -30,6 +30,7 @@ high state of flux, you're at risk of it changing without notice.
   - `Optional`
     - add `composeLens` (@gcanti)
     - add `composePrism` (@gcanti)
+    - add `setOption` (@gcanti)
 
 # 2.3.6
 

docs/modules/Optional.ts.md

@@ -47,6 +47,7 @@ Added in v2.3.0
   - [prop](#prop)
   - [props](#props)
   - [right](#right)
+  - [setOption](#setoption)
   - [some](#some)
   - [traverse](#traverse)
 - [compositions](#compositions)
@@ -262,6 +263,16 @@ export declare const right: <S, E, A>(sea: Optional<S, Either<E, A>>) => Optiona
 
 Added in v2.3.0
 
+## setOption
+
+**Signature**
+
+```ts
+export declare const setOption: <A>(a: A) => <S>(optional: Optional<S, A>) => (s: S) => O.Option<S>
+```
+
+Added in v2.3.7
+
 ## some
 
 Return a `Optional` from a `Optional` focused on the `Some` of a `Option` type.

src/Optional.ts

@@ -115,6 +115,12 @@ export const composePrism = <A, B>(ab: Prism<A, B>) => <S>(sa: Optional<S, A>):
 export const modifyOption: <A>(f: (a: A) => A) => <S>(optional: Optional<S, A>) => (s: S) => Option<S> =
   _.optionalModifyOption
 
+/**
+ * @category combinators
+ * @since 2.3.7
+ */
+export const setOption = <A>(a: A): (<S>(optional: Optional<S, A>) => (s: S) => Option<S>) => modifyOption(() => a)
+
 /**
  * @category combinators
  * @since 2.3.0

test/Optional.ts

@@ -191,4 +191,10 @@ describe('Optional', () => {
     assert.deepStrictEqual(f([1, 2, 3]), O.some([2, 2, 3]))
     assert.deepStrictEqual(f([-1, 2, 3]), O.none)
   })
+
+  it('setOption', () => {
+    const sa = pipe(_.id<ReadonlyArray<number>>(), _.index(0))
+    assert.deepStrictEqual(pipe(sa, _.setOption(2))([]), O.none)
+    assert.deepStrictEqual(pipe(sa, _.setOption(2))([1, 3]), O.some([2, 3]))
+  })
 })