fix(fetch): implement fully read body algorithm

lib/fetch/index.js

@@ -34,7 +34,8 @@ const {
   sameOrigin,
   isCancelled,
   isAborted,
-  isErrorLike
+  isErrorLike,
+  fullyReadBody
 } = require('./util')
 const { kState, kHeaders, kGuard, kRealm } = require('./symbols')
 const assert = require('assert')
@@ -738,11 +739,7 @@ async function mainFetch (fetchParams, recursive = false) {
     }
 
     // 4. Fully read response’s body given processBody and processBodyError.
-    try {
-      processBody(await response.arrayBuffer())
-    } catch (err) {
-      processBodyError(err)
-    }
+    await fullyReadBody(response.body, processBody, processBodyError)
   } else {
     // 21. Otherwise, run fetch finale given fetchParams and response.
     fetchFinale(fetchParams, response)
@@ -974,11 +971,7 @@ async function fetchFinale (fetchParams, response) {
     } else {
       // 4. Otherwise, fully read response’s body given processBody, processBodyError,
       // and fetchParams’s task destination.
-      try {
-        processBody(await response.body.stream.arrayBuffer())
-      } catch (err) {
-        processBodyError(err)
-      }
+      await fullyReadBody(response.body, processBody, processBodyError)
     }
   }
 }

lib/fetch/util.js

@@ -4,6 +4,7 @@ const { redirectStatus } = require('./constants')
 const { performance } = require('perf_hooks')
 const { isBlobLike, toUSVString, ReadableStreamFrom } = require('../core/util')
 const assert = require('assert')
+const { isUint8Array } = require('util/types')
 
 let File
 
@@ -438,6 +439,53 @@ function makeIterator (iterator, name) {
   return Object.setPrototypeOf({}, i)
 }
 
+/**
+ * @see https://fetch.spec.whatwg.org/#body-fully-read
+ */
+async function fullyReadBody (body, processBody, processBodyError) {
+  // 1. If taskDestination is null, then set taskDestination to
+  //    the result of starting a new parallel queue.
+
+  // 2. Let promise be the result of fully reading body as promise
+  //    given body.
+  try {
+    /** @type {Uint8Array[]} */
+    const chunks = []
+    let length = 0
+
+    const reader = body.stream.getReader()
+
+    while (true) {
+      const { done, value } = await reader.read()
+
+      if (done === true) {
+        break
+      }
+
+      // read-loop chunk steps
+      assert(isUint8Array(value))
+
+      chunks.push(value)
+      length += value.byteLength
+    }
+
+    // 3. Let fulfilledSteps given a byte sequence bytes be to queue
+    //    a fetch task to run processBody given bytes, with
+    //    taskDestination.
+    const fulfilledSteps = (bytes) => queueMicrotask(() => {
+      processBody(bytes)
+    })
+
+    fulfilledSteps(Buffer.concat(chunks, length))
+  } catch {
+    // 4. Let rejectedSteps be to queue a fetch task to run
+    //    processBodyError, with taskDestination.
+    queueMicrotask(() => processBodyError())
+  }
+
+  // 5. React to promise with fulfilledSteps and rejectedSteps.
+}
+
 /**
  * Fetch supports node >= 16.8.0, but Object.hasOwn was added in v16.9.0.
  */
@@ -477,5 +525,6 @@ module.exports = {
   isValidHeaderName,
   isValidHeaderValue,
   hasOwn,
-  isErrorLike
+  isErrorLike,
+  fullyReadBody
 }

test/fetch/client-fetch.js

@@ -536,3 +536,28 @@ test('Receiving non-Latin1 headers', async (t) => {
   t.same(lengths, [30, 34, 94, 104, 90])
   t.end()
 })
+
+// https://github.com/nodejs/undici/issues/1594
+// TODO(@KhafraDev): this test fails because of an integrity-mismatch check
+// that hasn't been implemented when this comment was written. Enable this
+// check once a resource's integrity is checked.
+// test('with RequestInit.integrity set', async (t) => {
+//   const body = 'Hello world'
+//   const hash = require('crypto').createHash('sha256').update(body).digest('hex')
+//
+//   const server = createServer((req, res) => {
+//     res.write(body)
+//     res.end()
+//   }).listen(0)
+//
+//   t.teardown(server.close.bind(server))
+//   await once(server, 'listening')
+//
+//   const response = await fetch(`http://localhost:${server.address().port}`, {
+//     integrity: `sha256-${hash}`
+//   })
+//
+//   const ab = await response.arrayBuffer()
+//
+//   t.same(new Uint8Array(ab), new TextEncoder().encode(body))
+// })