feat: at optic tests complete

optics/at.ts

@@ -23,8 +23,8 @@ export const atRecord = <A = never>(): At<
   at: (key) => ({
     get: (r) => O.fromNullable(r[key]),
     set: O.fold(
-      (a) => R.insertAt(key, a),
       () => R.deleteAt(key),
+      (a) => R.insertAt(key, a),
     ),
   }),
 });
@@ -37,12 +37,12 @@ export const atMap = <A = never>(): At<
   at: (key) => ({
     get: (m) => O.fromNullable(m.get(key)),
     set: O.fold(
-      (a) => (m) => m.set(key, a),
       () =>
         (m) => {
           m.delete(key);
           return m;
         },
+      (a) => (m) => m.set(key, a),
     ),
   }),
 });

optics/optional.ts

@@ -43,8 +43,8 @@ export const asTraversal = <S, A>(sa: Optional<S, A>): Traversal<S, A> => ({
         pipe(
           sa.getOption(s),
           O.fold(
-            (a) => pipe(fata(a), F.map((a: A) => sa.set(a)(s))),
             () => F.of(s),
+            (a) => pipe(fata(a), F.map((a: A) => sa.set(a)(s))),
           ),
         ),
 });
@@ -73,7 +73,7 @@ export const compose = <J, K>(jk: Optional<J, K>) =>
         pipe(
           ij.getOption(s),
           O.map(jk.set(b)),
-          O.fold(ij.set, () => identity),
+          O.fold(() => identity, ij.set),
         )(s),
   });
 
@@ -91,7 +91,7 @@ export const composeLens = <A, B>(ab: Lens<A, B>) =>
         pipe(
           sa.getOption(s),
           O.map(ab.set(b)),
-          O.fold(flow(sa.set, apply(s)), constant(s)),
+          O.fold(constant(s), flow(sa.set, apply(s))),
         ),
   });
 
@@ -109,8 +109,8 @@ export const composeTraversal = <A, B>(ab: Traversal<A, B>) =>
           pipe(
             sa.getOption(s),
             O.fold(
-              flow(ab.traverse(T)(fata), T.map(flow(sa.set, apply(s)))),
               constant(T.of(s)),
+              flow(ab.traverse(T)(fata), T.map(flow(sa.set, apply(s)))),
             ),
           ),
   });
@@ -138,7 +138,7 @@ export const modify = <A>(faa: (a: A) => A) =>
       pipe(
         sa.getOption(s),
         O.map(faa),
-        O.fold(flow(sa.set, apply(s)), constant(s)),
+        O.fold(constant(s), flow(sa.set, apply(s))),
       );
 
 export const traverse = <URI extends URIS>(T: TC.Traversable<URI>) => {

optics/prism.ts

@@ -62,8 +62,8 @@ export const asTraversal = <S, A>(sa: Prism<S, A>): Traversal<S, A> => ({
         pipe(
           sa.getOption(s),
           O.fold(
-            flow(fata, T.map(flow(getSet(sa), apply(s)))),
             () => T.of(s),
+            flow(fata, T.map(flow(getSet(sa), apply(s)))),
           ),
         ),
 });
@@ -103,7 +103,7 @@ export const composeLens = <A, B>(ab: Lens<A, B>) =>
       (s) =>
         pipe(
           sa.getOption(s),
-          O.fold(flow(ab.set(b), sa.reverseGet), () => s),
+          O.fold(() => s, flow(ab.set(b), sa.reverseGet)),
         ),
   });
 
@@ -114,7 +114,7 @@ export const composeOptional = <A, B>(ab: Optional<A, B>) =>
       (s) =>
         pipe(
           sa.getOption(s),
-          O.fold(flow(ab.set(b), sa.reverseGet), () => s),
+          O.fold(() => s, flow(ab.set(b), sa.reverseGet)),
         ),
   });
 
@@ -126,8 +126,8 @@ export const composeTraversal = <A, B>(ab: Traversal<A, B>) =>
           pipe(
             sa.getOption(s),
             O.fold(
-              flow(ab.traverse(A)(fata), A.map(sa.reverseGet)),
               constant(A.of(s)),
+              flow(ab.traverse(A)(fata), A.map(sa.reverseGet)),
             ),
           ),
   });

testing/optics/at.test.ts

@@ -0,0 +1,34 @@
+import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+
+import * as A from "../../optics/at.ts";
+import * as O from "../../option.ts";
+
+Deno.test("At atRecord", () => {
+  const at = A.atRecord<number>();
+  const { get, set } = at.at("one");
+
+  assertEquals(get({}), O.none);
+  assertEquals(get({ two: 1 }), O.none);
+  assertEquals(get({ one: 1 }), O.some(1));
+
+  assertEquals(set(O.none)({}), {});
+  assertEquals(set(O.none)({ one: 1 }), {});
+  assertEquals(set(O.some(1))({}), { one: 1 });
+  assertEquals(set(O.some(1))({ one: 2 }), { one: 1 });
+  assertEquals(set(O.some(1))({ one: 1 }), { one: 1 });
+});
+
+Deno.test("At atMap", () => {
+  const at = A.atMap<number>();
+  const { get, set } = at.at("one");
+
+  assertEquals(get(new Map()), O.none);
+  assertEquals(get(new Map([["one", 1]])), O.some(1));
+  assertEquals(get(new Map([["two", 1]])), O.none);
+
+  assertEquals(set(O.none)(new Map()), new Map());
+  assertEquals(set(O.none)(new Map([["one", 1]])), new Map());
+  assertEquals(set(O.some(1))(new Map()), new Map([["one", 1]]));
+  assertEquals(set(O.some(1))(new Map([["one", 2]])), new Map([["one", 1]]));
+  assertEquals(set(O.some(1))(new Map([["one", 1]])), new Map([["one", 1]]));
+});