ReadableStreamFrom pull until cannot on empty enqueu (nodejs#4002)

Author: KhafraDev

lib/core/util.js

@@ -600,20 +600,25 @@ function ReadableStreamFrom (iterable) {
       async start () {
         iterator = iterable[Symbol.asyncIterator]()
       },
-      async pull (controller) {
-        const { done, value } = await iterator.next()
-        if (done) {
-          queueMicrotask(() => {
-            controller.close()
-            controller.byobRequest?.respond(0)
-          })
-        } else {
-          const buf = Buffer.isBuffer(value) ? value : Buffer.from(value)
-          if (buf.byteLength) {
-            controller.enqueue(new Uint8Array(buf))
+      pull (controller) {
+        async function pull () {
+          const { done, value } = await iterator.next()
+          if (done) {
+            queueMicrotask(() => {
+              controller.close()
+              controller.byobRequest?.respond(0)
+            })
+          } else {
+            const buf = Buffer.isBuffer(value) ? value : Buffer.from(value)
+            if (buf.byteLength) {
+              controller.enqueue(new Uint8Array(buf))
+            } else {
+              return await pull()
+            }
           }
         }
-        return controller.desiredSize > 0
+
+        return pull()
       },
       async cancel () {
         await iterator.return()

test/fetch/issue-node-56474.js

@@ -0,0 +1,30 @@
+'use strict'
+
+const { test } = require('node:test')
+const { deepStrictEqual } = require('node:assert')
+const { Response } = require('../..')
+
+// https://github.com/nodejs/node/issues/56474
+test('ReadableStream empty enqueue then other enqueued', async () => {
+  const iterable = {
+    async * [Symbol.asyncIterator] () {
+      yield ''
+      yield '3'
+      yield '4'
+    }
+  }
+
+  const response = new Response(iterable)
+  deepStrictEqual(await response.text(), '34')
+})
+
+test('ReadableStream empty enqueue', async () => {
+  const iterable = {
+    async * [Symbol.asyncIterator] () {
+      yield ''
+    }
+  }
+
+  const response = new Response(iterable)
+  deepStrictEqual(await response.text(), '')
+})