streams: simplify readableStreamFromIterable

Author: aduh95

lib/internal/webstreams/readablestream.js

@@ -24,6 +24,7 @@ const {
   Symbol,
   SymbolAsyncIterator,
   SymbolDispose,
+  SymbolIterator,
   SymbolToStringTag,
   TypedArrayPrototypeGetLength,
   Uint8Array,
@@ -32,6 +33,7 @@ const {
 const {
   AbortError,
   codes: {
+    ERR_ARG_NOT_ITERABLE,
     ERR_ILLEGAL_CONSTRUCTOR,
     ERR_INVALID_ARG_TYPE,
     ERR_INVALID_ARG_VALUE,
@@ -110,8 +112,6 @@ const {
   nonOpCancel,
   nonOpPull,
   nonOpStart,
-  getIterator,
-  iteratorNext,
   kType,
   kState,
 } = require('internal/webstreams/util');
@@ -1341,41 +1341,36 @@ function createReadableStreamState() {
 
 function readableStreamFromIterable(iterable) {
   let stream;
-  const iteratorRecord = getIterator(iterable, 'async');
-
+  const iteratorGetter = iterable[SymbolAsyncIterator] ?? iterable[SymbolIterator];
+  if (iteratorGetter == null || typeof iteratorGetter !== 'function') {
+    throw new ERR_ARG_NOT_ITERABLE(iterable);
+  }
+  const iterator = FunctionPrototypeCall(iteratorGetter, iterable);
   const startAlgorithm = nonOpStart;
 
   async function pullAlgorithm() {
-    const nextResult = iteratorNext(iteratorRecord);
-    const nextPromise = PromiseResolve(nextResult);
-    return PromisePrototypeThen(nextPromise, (iterResult) => {
-      if (typeof iterResult !== 'object' || iterResult === null) {
-        throw new ERR_INVALID_STATE.TypeError(
-          'The promise returned by the iterator.next() method must fulfill with an object');
-      }
-      if (iterResult.done) {
-        readableStreamDefaultControllerClose(stream[kState].controller);
-      } else {
-        readableStreamDefaultControllerEnqueue(stream[kState].controller, iterResult.value);
-      }
-    });
+    const iterResult = await iterator.next();
+    if (typeof iterResult !== 'object' || iterResult === null) {
+      throw new ERR_INVALID_STATE.TypeError(
+        'The promise returned by the iterator.next() method must fulfill with an object');
+    }
+    if (iterResult.done) {
+      readableStreamDefaultControllerClose(stream[kState].controller);
+    } else {
+      readableStreamDefaultControllerEnqueue(stream[kState].controller, await iterResult.value);
+    }
   }
 
   async function cancelAlgorithm(reason) {
-    const iterator = iteratorRecord.iterator;
     const returnMethod = iterator.return;
     if (returnMethod === undefined) {
-      return PromiseResolve();
+      return;
+    }
+    const iterResult = await FunctionPrototypeCall(returnMethod, iterator, reason);
+    if (typeof iterResult !== 'object' || iterResult === null) {
+      throw new ERR_INVALID_STATE.TypeError(
+        'The promise returned by the iterator.return() method must fulfill with an object');
     }
-    const returnResult = FunctionPrototypeCall(returnMethod, iterator, reason);
-    const returnPromise = PromiseResolve(returnResult);
-    return PromisePrototypeThen(returnPromise, (iterResult) => {
-      if (typeof iterResult !== 'object' || iterResult === null) {
-        throw new ERR_INVALID_STATE.TypeError(
-          'The promise returned by the iterator.return() method must fulfill with an object');
-      }
-      return undefined;
-    });
   }
 
   stream = createReadableStream(

lib/internal/webstreams/util.js

@@ -13,16 +13,12 @@ const {
   PromisePrototypeThen,
   ReflectGet,
   Symbol,
-  SymbolAsyncIterator,
-  SymbolIterator,
   Uint8Array,
 } = primordials;
 
 const {
   codes: {
-    ERR_ARG_NOT_ITERABLE,
     ERR_INVALID_ARG_VALUE,
-    ERR_INVALID_STATE,
   },
 } = require('internal/errors');
 
@@ -208,64 +204,6 @@ function lazyTransfer() {
   return transfer;
 }
 
-function createAsyncFromSyncIterator(syncIteratorRecord) {
-  const syncIterable = {
-    [SymbolIterator]: () => syncIteratorRecord.iterator,
-  };
-
-  const asyncIterator = (async function* () {
-    return yield* syncIterable;
-  }());
-
-  const nextMethod = asyncIterator.next;
-  return { iterator: asyncIterator, nextMethod, done: false };
-}
-
-// Refs: https://tc39.es/ecma262/#sec-getiterator
-function getIterator(obj, kind = 'sync', method) {
-  if (method === undefined) {
-    if (kind === 'async') {
-      method = obj[SymbolAsyncIterator];
-      if (method == null) {
-        const syncMethod = obj[SymbolIterator];
-
-        if (syncMethod === undefined) {
-          throw new ERR_ARG_NOT_ITERABLE(obj);
-        }
-
-        const syncIteratorRecord = getIterator(obj, 'sync', syncMethod);
-        return createAsyncFromSyncIterator(syncIteratorRecord);
-      }
-    } else {
-      method = obj[SymbolIterator];
-    }
-  }
-
-  if (method === undefined) {
-    throw new ERR_ARG_NOT_ITERABLE(obj);
-  }
-
-  const iterator = FunctionPrototypeCall(method, obj);
-  if (typeof iterator !== 'object' || iterator === null) {
-    throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
-  }
-  const nextMethod = iterator.next;
-  return { iterator, nextMethod, done: false };
-}
-
-function iteratorNext(iteratorRecord, value) {
-  let result;
-  if (value === undefined) {
-    result = FunctionPrototypeCall(iteratorRecord.nextMethod, iteratorRecord.iterator);
-  } else {
-    result = FunctionPrototypeCall(iteratorRecord.nextMethod, iteratorRecord.iterator, [value]);
-  }
-  if (typeof result !== 'object' || result === null) {
-    throw new ERR_INVALID_STATE.TypeError('The iterator.next() method must return an object');
-  }
-  return result;
-}
-
 module.exports = {
   ArrayBufferViewGetBuffer,
   ArrayBufferViewGetByteLength,
@@ -292,8 +230,6 @@ module.exports = {
   nonOpPull,
   nonOpStart,
   nonOpWrite,
-  getIterator,
-  iteratorNext,
   kType,
   kState,
 };