Optic: add nonNullable

.changeset/slimy-trees-notice.md

@@ -0,0 +1,5 @@
+---
+"@fp-ts/optic": patch
+---
+
+Optic: add nonNullable

README.md

@@ -42,11 +42,9 @@ flowchart TD
 Let's say we have an employee and we need to upper case the first character of his company street name.
 
 ```ts
-import * as O from "@fp-ts/data/Option";
-
 interface Street {
   num: number;
-  name: O.Option<string>;
+  name: string | null;
 }
 interface Address {
   city: string;
@@ -69,7 +67,7 @@ const from: Employee = {
       city: "london",
       street: {
         num: 23,
-        name: O.some("high street"),
+        name: "high street",
       },
     },
   },
@@ -83,7 +81,7 @@ const to: Employee = {
       city: "london",
       street: {
         num: 23,
-        name: O.some("High street"),
+        name: "High street",
       },
     },
   },
@@ -94,16 +92,15 @@ Let's see what could we do with `@fp-ts/optic`
 
 ```ts
 import * as Optic from "@fp-ts/optic";
-import * as OptionOptic from "@fp-ts/optic/data/Option";
 import * as StringOptic from "@fp-ts/optic/data/string";
 
 const _name: Optic.Optional<Employee, string> = Optic.id<Employee>()
-  .at("company") // Lens<Employee, Company>
-  .at("address") // Lens<Employee, Company>
-  .at("street") // Lens<<Employee, Company>
-  .at("name") // Lens<Street, O.Option<string>>
-  .compose(OptionOptic.some()) // Prism<O.Option<string>, string>
-  .compose(StringOptic.index(0)); // Optional<string, string>
+  .at("company")
+  .at("address")
+  .at("street")
+  .at("name")
+  .nonNullable()
+  .compose(StringOptic.index(0));
 
 const capitalize = (s: string): string => s.toUpperCase();
 

src/data/Option.ts

@@ -18,7 +18,7 @@ export const none = <A>(): Prism<Option<A>, void> =>
       () => E.right<void>(undefined),
       (a) => E.left(Error(`some(${a}) did not satisfy isNone`))
     ),
-    (_): Option<A> => O.none
+    (): Option<A> => O.none
   )
 
 /**
@@ -35,5 +35,5 @@ export const some: {
       () => E.left([Error("none did not satisfy isSome"), O.none]),
       (a) => E.right(a)
     ),
-    (b) => O.some(b)
+    O.some
   )

src/index.ts

@@ -94,6 +94,9 @@ export interface Optic<
     key: Key
   ): Optional<S, A[Key]>
 
+  nonNullable<S, A>(this: Prism<S, A>): Prism<S, NonNullable<A>>
+  nonNullable<S, A>(this: Optional<S, A>): Optional<S, NonNullable<A>>
+
   get<S, T, A, B>(this: PolyLens<S, T, A, B>, s: S): A
 
   getOption<S, A>(this: Getter<S, A>, s: S): Option<A>
@@ -140,6 +143,10 @@ class Builder<
     return this.compose(at<any, any>(key))
   }
 
+  nonNullable(): any {
+    return this.compose(nonNullable())
+  }
+
   get<S, T, A, B>(this: PolyLens<S, T, A, B>, s: S): A {
     return pipe(this.getOptic(s), E.getOrThrow(identity))
   }
@@ -433,17 +440,6 @@ export const cons: {
     ([head, tail]): ReadonlyArray<B> => [head, ...tail]
   )
 
-/**
- * An optic that accesses the `NonNullable` case of a nullable type.
- *
- * @since 1.0.0
- */
-export const nonNullable = <S>(): Prism<S, NonNullable<S>> =>
-  prism(
-    (s) => s == null ? E.left(new Error(`${s} did not satisfy isNonNullable`)) : E.right(s as any),
-    identity
-  )
-
 /**
  * An optic that accesses the case specified by a predicate.
  *
@@ -454,11 +450,19 @@ export const filter: {
   <S extends A, A = S>(predicate: Predicate<A>): Prism<S, S>
 } = <S>(predicate: Predicate<S>): Prism<S, S> =>
   prism(
-    (s) =>
-      predicate(s) ? E.right(s) : E.left(new Error(`${s} did not satisfy the specified predicate`)),
+    (s) => predicate(s) ? E.right(s) : E.left(new Error(`${s} did not satisfy ${predicate.name}`)),
     identity
   )
 
+const isNonNullable = <S>(s: S): s is NonNullable<S> => s != null
+
+/**
+ * An optic that accesses the `NonNullable` case of a nullable type.
+ *
+ * @since 1.0.0
+ */
+export const nonNullable = <S>(): Prism<S, NonNullable<S>> => filter(isNonNullable)
+
 /**
  * @since 1.0.0
  */

test/examples.ts

@@ -1,13 +1,11 @@
-import * as O from "@fp-ts/data/Option"
 import * as Optic from "@fp-ts/optic"
-import * as OptionOptic from "@fp-ts/optic/data/Option"
 import * as StringOptic from "@fp-ts/optic/data/String"
 
 describe("examples", () => {
   it("README", () => {
     interface Street {
       num: number
-      name: O.Option<string>
+      name: string | null
     }
     interface Address {
       city: string
@@ -30,7 +28,7 @@ describe("examples", () => {
           city: "london",
           street: {
             num: 23,
-            name: O.some("high street")
+            name: "high street"
           }
         }
       }
@@ -44,19 +42,19 @@ describe("examples", () => {
           city: "london",
           street: {
             num: 23,
-            name: O.some("High street")
+            name: "High street"
           }
         }
       }
     }
 
     const _name: Optic.Optional<Employee, string> = Optic.id<Employee>()
-      .at("company") // Lens<Employee, Company>
-      .at("address") // Lens<Employee, Company>
-      .at("street") // Lens<<Employee, Company>
-      .at("name") // Lens<Street, O.Option<string>>
-      .compose(OptionOptic.some()) // Prism<O.Option<string>, string>
-      .compose(StringOptic.index(0)) // Optional<string, string>
+      .at("company")
+      .at("address")
+      .at("street")
+      .at("name")
+      .nonNullable()
+      .compose(StringOptic.index(0))
 
     const capitalize = (s: string): string => s.toUpperCase()