Update es-iterator-helpers concat

packages/npm/es-iterator-helpers/Iterator.concat/implementation.js

@@ -42,49 +42,81 @@ module.exports =
               '`Iterator.concat` requires all arguments to be iterable'
             )
           }
-          // (Handled by getMethod, which throws if method is missing or not callable.)
-          records[i] = {
-            iterable,
-            openMethod: getMethod(iterable, SymbolIterator)
-          }
+          // Step 2.d: Append the Record { [[OpenMethod]]: method, [[Iterable]]: item } to iterables.
+          records[i] = { iterable, openMethod: method }
         }
-        let index = 0
-        let innerIterator = null
-        // Step 3: Let closure be a new Abstract Closure that captures iterables.
+
+        // Step 3: Let closure be a new Abstract Closure with no parameters that captures iterables and performs the following steps when called.
+        let iterablesIndex = 0
+        let innerIteratorRecord
         const closure = {
-          // This closure will perform the steps defined in Step 3.a.
           next() {
-            while (index < length) {
-              if (!innerIterator) {
-                // If we haven't initialized an inner iterator yet, do so
-                const { iterable, openMethod } = records[index]
-                // Step 3.a.i: Let iter be Call(iterable.[[OpenMethod]], iterable.[[Iterable]]).
-                innerIterator = ReflectApply(openMethod, iterable, [])
+            // Step 3.a: For each Record iterable of iterables, do.
+            while (iterablesIndex < length) {
+              // Step 3.a.i: Let iter be ? Call(iterable.[[OpenMethod]], iterable.[[Iterable]]).
+              if (innerIteratorRecord === undefined) {
+                const { iterable, openMethod } = records[iterablesIndex]
+                const innerIterator = ReflectApply(openMethod, iterable, [])
                 // Step 3.a.ii: If iter is not an Object, throw a TypeError exception.
                 ensureObject(innerIterator, 'iterator')
+                // Step 3.a.iii: Let iteratorRecord be ? GetIteratorDirect(iter).
+                innerIteratorRecord = getIteratorDirect(innerIterator)
               }
-              // Step 3.a.iii: Let iteratorRecord be GetIteratorDirect(iter).
-              const { next } = getIteratorDirect(innerIterator)
-              // Step 3.a.iv: Let innerAlive be true.
-              // (Handled by the loop structure)
-              // Step 3.a.v: Repeat, while innerAlive is true.
-              const result = ReflectApply(next, innerIterator, [])
-              if (!result.done) {
-                // Step 3.a.v.3.a: Yield the value of the iterator.
-                return result
+              const { iterator, next } = innerIteratorRecord
+              try {
+                // Step 3.a.v.1: Let iteratorResult be ? IteratorStep(iteratorRecord).
+                const result = ReflectApply(next, iterator, [])
+                // Step 3.a.v.3: Yield value if not done.
+                if (!result.done) {
+                  return { value: result.value, done: false }
+                }
+              } catch (error) {
+                // Step 3.a.v.3.b.i: Handle abrupt completion and rethrow error.
+                innerIteratorRecord = undefined
+                iterablesIndex += 1
+                throw error
               }
-              // Step 3.a.v.2: If innerValue is done, move to the next iterable.
-              innerIterator = null
-              index += 1
+              // Step 3.a.v.2: Set innerAlive to false and move to the next iterable.
+              innerIteratorRecord = undefined
+              iterablesIndex += 1
             }
             // Step 3.b: Return Completion(undefined).
             return { value: undefined, done: true }
+          },
+
+          return() {
+            // Handle iterator return if it exists.
+            if (innerIteratorRecord) {
+              const { iterator } = innerIteratorRecord
+              innerIteratorRecord = undefined
+              const returnMethod = getMethod(iterator, 'return')
+              if (typeof returnMethod === 'function') {
+                return ReflectApply(returnMethod, iterator, [])
+              }
+            }
+            return { value: undefined, done: true }
+          },
+
+          throw(error) {
+            // Handle iterator throw if it exists.
+            if (innerIteratorRecord) {
+              const { iterator } = innerIteratorRecord
+              innerIteratorRecord = undefined
+              const throwMethod = getMethod(iterator, 'throw')
+              if (typeof throwMethod === 'function') {
+                return ReflectApply(throwMethod, iterator, [error])
+              }
+            }
+            // Skip remaining iterables and propagate the error.
+            iterablesIndex = length
+            throw error
           }
         }
-        // Step 4: Create wrapper using CreateIteratorFromClosure.
+
+        // Step 4: Let gen be CreateIteratorFromClosure(closure, "Iterator Helper", %IteratorHelperPrototype%, « [[UnderlyingIterators]] »).
         const wrapper = createIteratorFromClosure(closure)
-        // Step 5: Set wrapper.[[UnderlyingIterator]] to iteratorRecord.
+        // Step 5: Set gen.[[UnderlyingIterators]] to a new empty List.
         setUnderlyingIterator(wrapper, closure)
-        // Step 6: Return wrapper.
+        // Step 6: Return gen.
         return wrapper
       }