stream: make additional minor tweaks in stream/iter

Author: jasnell

lib/internal/streams/iter/from.js

@@ -63,42 +63,23 @@ function isPrimitiveChunk(value) {
   return typeof value === 'string' || isArrayBuffer(value) || ArrayBufferIsView(value);
 }
 
-/**
- * Check if value implements ToStreamable protocol.
- * @returns {boolean}
- */
-function isToStreamable(value) {
-  return hasProtocol(value, toStreamable);
-}
-
-function isToAsyncStreamable(value) {
-  return hasProtocol(value, toAsyncStreamable);
-}
-
 /**
  * Check if value is a sync iterable (has Symbol.iterator).
  * @returns {boolean}
  */
 function isSyncIterable(value) {
-  return (
-    value !== null &&
-    typeof value === 'object' &&
-    SymbolIterator in value &&
-    typeof value[SymbolIterator] === 'function'
-  );
+  // We do not consider regular strings to be sync iterables in this context.
+  // We don't care about boxed strings (String objects) since they are uncommon.
+  return typeof value !== 'string' &&
+      typeof value?.[SymbolIterator] === 'function';
 }
 
 /**
  * Check if value is an async iterable (has Symbol.asyncIterator).
  * @returns {boolean}
  */
 function isAsyncIterable(value) {
-  return (
-    value !== null &&
-    typeof value === 'object' &&
-    SymbolAsyncIterator in value &&
-    typeof value[SymbolAsyncIterator] === 'function'
-  );
+  return typeof value?.[SymbolAsyncIterator] === 'function';
 }
 
 // =============================================================================
@@ -138,7 +119,6 @@ function primitiveToUint8Array(chunk) {
   );
 }
 
-
 // =============================================================================
 // Sync Normalization (for fromSync and sync contexts)
 // =============================================================================
@@ -156,7 +136,7 @@ function* normalizeSyncValue(value) {
   }
 
   // Handle ToStreamable protocol
-  if (isToStreamable(value)) {
+  if (hasProtocol(value, toStreamable)) {
     const result = FunctionPrototypeCall(value[toStreamable], value);
     yield* normalizeSyncValue(result);
     return;
@@ -260,7 +240,7 @@ async function* normalizeAsyncValue(value) {
   }
 
   // Handle ToAsyncStreamable protocol (check before ToStreamable)
-  if (isToAsyncStreamable(value)) {
+  if (hasProtocol(value, toAsyncStreamable)) {
     const result = FunctionPrototypeCall(value[toAsyncStreamable], value);
     if (isPromise(result)) {
       yield* normalizeAsyncValue(await result);
@@ -271,7 +251,7 @@ async function* normalizeAsyncValue(value) {
   }
 
   // Handle ToStreamable protocol
-  if (isToStreamable(value)) {
+  if (hasProtocol(value, toStreamable)) {
     const result = FunctionPrototypeCall(value[toStreamable], value);
     yield* normalizeAsyncValue(result);
     return;
@@ -593,8 +573,6 @@ module.exports = {
   isAsyncIterable,
   isPrimitiveChunk,
   isSyncIterable,
-  isToAsyncStreamable,
-  isToStreamable,
   isUint8ArrayBatch,
   normalizeAsyncSource,
   normalizeAsyncValue,

lib/internal/streams/iter/pull.js

@@ -58,12 +58,7 @@ const {
  * @returns {boolean}
  */
 function hasMethod(value, name) {
-  return (
-    value !== null &&
-    typeof value === 'object' &&
-    name in value &&
-    typeof value[name] === 'function'
-  );
+  return typeof value?.[name] === 'function';
 }
 
 /**