Return the most recent {value, done} object from touchNext

Author: stasm

src/cached_async_iterable.mjs

@@ -79,5 +79,8 @@ export default class CachedAsyncIterable {
                 seen.push(await iterator.next());
             }
         }
+        // Return the last cached {value, done} object to allow the calling
+        // code to decide if it needs to call touchNext again.
+        return seen[seen.length - 1];
     }
 }

src/cached_sync_iterable.mjs

@@ -49,5 +49,8 @@ export default class CachedSyncIterable {
                 seen.push(iterator.next());
             }
         }
+        // Return the last cached {value, done} object to allow the calling
+        // code to decide if it needs to call touchNext again.
+        return seen[seen.length - 1];
     }
 }

test/cached_async_iterable_test.js

@@ -241,5 +241,21 @@ suite("CachedAsyncIterable", function() {
             }
             assert.deepEqual(values, [o1, o2]);
         });
+
+        test("returns the most recent {value, done} object", async function() {
+            const iterable = new CachedAsyncIterable([o1, o2]);
+            assert.deepEqual(
+                await iterable.touchNext(),
+                {value: o1, done: false});
+            assert.deepEqual(
+                await iterable.touchNext(),
+                {value: o2, done: false});
+            assert.deepEqual(
+                await iterable.touchNext(),
+                {value: undefined, done: true});
+            assert.deepEqual(
+                await iterable.touchNext(),
+                {value: undefined, done: true});
+        });
     });
 });

test/cached_sync_iterable_test.js

@@ -137,5 +137,21 @@ suite("CachedSyncIterable", function() {
             iterable.touchNext();
             assert.deepEqual([...iterable], [o1, o2]);
         });
+
+        test("returns the most recent {value, done} object", function() {
+            const iterable = new CachedSyncIterable([o1, o2]);
+            assert.deepEqual(
+                iterable.touchNext(),
+                {value: o1, done: false});
+            assert.deepEqual(
+                iterable.touchNext(),
+                {value: o2, done: false});
+            assert.deepEqual(
+                iterable.touchNext(),
+                {value: undefined, done: true});
+            assert.deepEqual(
+                iterable.touchNext(),
+                {value: undefined, done: true});
+        });
     });
 });