Follow up #1455 to add Set behavior for no-op maps

leebyron · leebyron · commit 5726bd18de1c · 2018-05-17T16:57:19.000+02:00
diff --git a/__tests__/Set.ts b/__tests__/Set.ts
@@ -92,6 +92,12 @@ describe('Set', () => {
     expect(s.toObject()).toEqual({ a: 'a', b: 'b', c: 'c' });
   });
 
+  it('maps no-ops return the same reference', () => {
+    const s = Set([1, 2, 3]);
+    const r = s.map(value => value);
+    expect(r).toBe(s);
+  });
+
   it('unions an unknown collection of Sets', () => {
     const abc = Set(['a', 'b', 'c']);
     const cat = Set(['c', 'a', 't']);
diff --git a/src/Set.js b/src/Set.js
@@ -80,6 +80,10 @@ export class Set extends SetCollection {
 
   // @pragma Composition
 
+  map(mapper, context) {
+    return updateSet(this, this._map.map(v => mapper(v, v, this), context));
+  }
+
   union(...iters) {
     iters = iters.filter(x => x.size !== 0);
     if (iters.length === 0) {
diff --git a/type-definitions/Immutable.d.ts b/type-definitions/Immutable.d.ts
@@ -1714,9 +1714,6 @@ declare module Immutable {
      *
      *     Set([1,2]).map(x => 10 * x)
      *     // Set [10,20]
-     *
-     * Note: `map()` always returns a new instance, even if it produced the same
-     * value at every step.
      */
     map<M>(
       mapper: (value: T, key: T, iter: this) => M,
@@ -1816,9 +1813,6 @@ declare module Immutable {
      *
      *     OrderedSet([ 1, 2 ]).map(x => 10 * x)
      *     // OrderedSet [10, 20]
-     *
-     * Note: `map()` always returns a new instance, even if it produced the same
-     * value at every step.
      */
     map<M>(
       mapper: (value: T, key: T, iter: this) => M,
