From 28868eaad43388a2e54ebe6703d1bb35c4d3b779 Mon Sep 17 00:00:00 2001
From: gcanti <giulio.canti@gmail.com>
Date: Mon, 13 Jul 2020 20:06:10 +0200
Subject: [PATCH] Optional: add missing `fromNullable` combinator, closes #133

---
 CHANGELOG.md                |  2 ++
 docs/modules/Optional.ts.md | 13 +++++++++++++
 src/Optional.ts             | 10 ++++++++++
 src/Prism.ts                | 16 ++++++----------
 test/Optional.ts            | 13 +++++++++++++
 5 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4c9841..4b19323 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,8 @@ high state of flux, you're at risk of it changing without notice.
   - `Prism`
     - (\*) remove `fromSome` constructor (@gcanti)
     - (\*) change `fromNullable` signature (@gcanti)
+  - `Optional`
+    - add missing `fromNullable` combinator, closes #133 (@gcanti)
 
 (\*) breaking change
 
diff --git a/docs/modules/Optional.ts.md b/docs/modules/Optional.ts.md
index ec222fc..62b37c8 100644
--- a/docs/modules/Optional.ts.md
+++ b/docs/modules/Optional.ts.md
@@ -37,6 +37,7 @@ Added in v2.3.0
   - [component](#component)
   - [filter](#filter)
   - [findFirst](#findfirst)
+  - [fromNullable](#fromnullable)
   - [index](#index)
   - [key](#key)
   - [left](#left)
@@ -126,6 +127,18 @@ export declare const findFirst: <A>(predicate: Predicate<A>) => <S>(sa: Optional
 
 Added in v2.3.2
 
+## fromNullable
+
+Return an `Optional` from a `Optional` focused on a nullable value
+
+**Signature**
+
+```ts
+export declare const fromNullable: <S, A>(sa: Optional<S, A>) => Optional<S, NonNullable<A>>
+```
+
+Added in v2.3.3
+
 ## index
 
 Return a `Optional` from a `Optional` focused on a `ReadonlyArray`
diff --git a/src/Optional.ts b/src/Optional.ts
index 4b3b9c7..a8b4419 100644
--- a/src/Optional.ts
+++ b/src/Optional.ts
@@ -100,6 +100,16 @@ export const modifyOption: <A>(f: (a: A) => A) => <S>(optional: Optional<S, A>)
  */
 export const modify: <A>(f: (a: A) => A) => <S>(optional: Optional<S, A>) => (s: S) => S = _.optionalModify
 
+/**
+ * Return an `Optional` from a `Optional` focused on a nullable value
+ *
+ * @category combinators
+ * @since 2.3.3
+ */
+export const fromNullable: <S, A>(sa: Optional<S, A>) => Optional<S, NonNullable<A>> =
+  /*#__PURE__*/
+  compose(_.prismAsOptional(_.prismFromNullable()))
+
 /**
  * @category combinators
  * @since 2.3.0
diff --git a/src/Prism.ts b/src/Prism.ts
index 0470045..f148884 100644
--- a/src/Prism.ts
+++ b/src/Prism.ts
@@ -120,6 +120,12 @@ export const composeOptional = <A, B>(ab: Optional<A, B>) => <S>(sa: Prism<S, A>
 // combinators
 // -------------------------------------------------------------------------------------
 
+/**
+ * @category combinators
+ * @since 2.3.0
+ */
+export const set: <A>(a: A) => <S>(sa: Prism<S, A>) => (s: S) => S = _.prismSet
+
 /**
  * @category combinators
  * @since 2.3.0
@@ -142,16 +148,6 @@ export const fromNullable: <S, A>(sa: Prism<S, A>) => Prism<S, NonNullable<A>> =
   /*#__PURE__*/
   compose(_.prismFromNullable())
 
-/**
- * @category combinators
- * @since 2.3.0
- */
-export const set: <A>(a: A) => <S>(sa: Prism<S, A>) => (s: S) => S = _.prismSet
-
-// -------------------------------------------------------------------------------------
-// combinators
-// -------------------------------------------------------------------------------------
-
 /**
  * @category combinators
  * @since 2.3.0
diff --git a/test/Optional.ts b/test/Optional.ts
index 28e765f..7ed2552 100644
--- a/test/Optional.ts
+++ b/test/Optional.ts
@@ -142,4 +142,17 @@ describe('Optional', () => {
     )
     assert.deepStrictEqual(modify(O.some({ a: ['a'] })), O.some({ a: ['A'] }))
   })
+
+  it('fromNullable', () => {
+    interface S {
+      a?: number
+    }
+    const sa = pipe(_.id<S>(), _.prop('a'), _.fromNullable)
+    assert.deepStrictEqual(sa.getOption({}), O.none)
+    assert.deepStrictEqual(sa.getOption({ a: undefined }), O.none)
+    assert.deepStrictEqual(sa.getOption({ a: 1 }), O.some(1))
+    assert.deepStrictEqual(sa.set(2)({}), {})
+    assert.deepStrictEqual(sa.set(2)({ a: undefined }), { a: undefined })
+    assert.deepStrictEqual(sa.set(2)({ a: 1 }), { a: 2 })
+  })
 })