fetch: avoid async iteration when request.body is null (#1303)

* fetch: avoid iteration when request.body is null

* slightly simplify

Co-authored-by: Robert Nagy <ronagy@icloud.com>

lib/fetch/index.js

@@ -1664,61 +1664,62 @@ async function httpNetworkFetch (
   //        2. Otherwise, return a network error.
 
   // To transmit request’s body body, run these steps:
-  const requestBody = (async function * () {
-    // 1. If body is null and fetchParams’s process request end-of-body is
-    // non-null, then queue a fetch task given fetchParams’s process request
-    // end-of-body and fetchParams’s task destination.
-    if (request.body == null && fetchParams.processRequestEndOfBody) {
-      queueMicrotask(() => fetchParams.processRequestEndOfBody())
-    } else if (request.body != null) {
-      // 2. Otherwise, if body is non-null:
-
-      //    1. Let processBodyChunk given bytes be these steps:
-      const processBodyChunk = async function * (bytes) {
-        // 1. If the ongoing fetch is terminated, then abort these steps.
-        if (isCancelled(fetchParams)) {
-          return
-        }
+  let requestBody = null
+  // 1. If body is null and fetchParams’s process request end-of-body is
+  // non-null, then queue a fetch task given fetchParams’s process request
+  // end-of-body and fetchParams’s task destination.
+  if (request.body == null && fetchParams.processRequestEndOfBody) {
+    queueMicrotask(() => fetchParams.processRequestEndOfBody())
+  } else if (request.body != null) {
+    // 2. Otherwise, if body is non-null:
+
+    //    1. Let processBodyChunk given bytes be these steps:
+    const processBodyChunk = async function * (bytes) {
+      // 1. If the ongoing fetch is terminated, then abort these steps.
+      if (isCancelled(fetchParams)) {
+        return
+      }
 
-        // 2. Run this step in parallel: transmit bytes.
-        yield bytes
+      // 2. Run this step in parallel: transmit bytes.
+      yield bytes
 
-        // 3. If fetchParams’s process request body is non-null, then run
-        // fetchParams’s process request body given bytes’s length.
-        fetchParams.processRequestBodyChunkLength?.(bytes.byteLength)
-      }
+      // 3. If fetchParams’s process request body is non-null, then run
+      // fetchParams’s process request body given bytes’s length.
+      fetchParams.processRequestBodyChunkLength?.(bytes.byteLength)
+    }
 
-      // 2. Let processEndOfBody be these steps:
-      const processEndOfBody = () => {
-        // 1. If fetchParams is canceled, then abort these steps.
-        if (isCancelled(fetchParams)) {
-          return
-        }
+    // 2. Let processEndOfBody be these steps:
+    const processEndOfBody = () => {
+      // 1. If fetchParams is canceled, then abort these steps.
+      if (isCancelled(fetchParams)) {
+        return
+      }
 
-        // 2. If fetchParams’s process request end-of-body is non-null,
-        // then run fetchParams’s process request end-of-body.
-        if (fetchParams.processRequestEndOfBody) {
-          fetchParams.processRequestEndOfBody()
-        }
+      // 2. If fetchParams’s process request end-of-body is non-null,
+      // then run fetchParams’s process request end-of-body.
+      if (fetchParams.processRequestEndOfBody) {
+        fetchParams.processRequestEndOfBody()
       }
+    }
 
-      // 3. Let processBodyError given e be these steps:
-      const processBodyError = (e) => {
-        // 1. If fetchParams is canceled, then abort these steps.
-        if (isCancelled(fetchParams)) {
-          return
-        }
+    // 3. Let processBodyError given e be these steps:
+    const processBodyError = (e) => {
+      // 1. If fetchParams is canceled, then abort these steps.
+      if (isCancelled(fetchParams)) {
+        return
+      }
 
-        // 2. If e is an "AbortError" DOMException, then abort fetchParams’s controller.
-        if (e.name === 'AbortError') {
-          fetchParams.controller.abort()
-        } else {
-          fetchParams.controller.terminate(e)
-        }
+      // 2. If e is an "AbortError" DOMException, then abort fetchParams’s controller.
+      if (e.name === 'AbortError') {
+        fetchParams.controller.abort()
+      } else {
+        fetchParams.controller.terminate(e)
       }
+    }
 
-      // 4. Incrementally read request’s body given processBodyChunk, processEndOfBody,
-      // processBodyError, and fetchParams’s task destination.
+    // 4. Incrementally read request’s body given processBodyChunk, processEndOfBody,
+    // processBodyError, and fetchParams’s task destination.
+    requestBody = (async function * () {
       try {
         for await (const bytes of request.body.stream) {
           yield * processBodyChunk(bytes)
@@ -1727,8 +1728,8 @@ async function httpNetworkFetch (
       } catch (err) {
         processBodyError(err)
       }
-    }
-  })()
+    })()
+  }
 
   try {
     const { body, status, statusText, headersList } = await dispatch({ body: requestBody })