feat(fetch): accept async iterables for body (#26882)

Reland of #24623, but with a fix for `String` objects.

Co-authored-by: crowlkats <crowlkats@toaxl.com>

2 files changed, 16 insertions, 0 deletions

diff --git a/ext/fetch/22_body.js b/ext/fetch/22_body.js
index 61a06b4af..c7e977c0b 100644
--- a/ext/fetch/22_body.js
+++ b/ext/fetch/22_body.js
@@ -15,6 +15,7 @@ import { core, primordials } from "ext:core/mod.js";
 const {
   isAnyArrayBuffer,
   isArrayBuffer,
+  isStringObject,
 } = core;
 const {
   ArrayBufferIsView,
@@ -466,6 +467,8 @@ function extractBody(object) {
     if (object.locked || isReadableStreamDisturbed(object)) {
       throw new TypeError("ReadableStream is locked or disturbed");
     }
+  } else if (object[webidl.AsyncIterable] === webidl.AsyncIterable) {
+    stream = ReadableStream.from(object.open());
   }
   if (typeof source === "string") {
     // WARNING: this deviates from spec (expects length to be set)
@@ -483,6 +486,9 @@ function extractBody(object) {
   return { body, contentType };
 }
 
+webidl.converters["async iterable<Uint8Array>"] = webidl
+  .createAsyncIterableConverter(webidl.converters.Uint8Array);
+
 webidl.converters["BodyInit_DOMString"] = (V, prefix, context, opts) => {
   // Union for (ReadableStream or Blob or ArrayBufferView or ArrayBuffer or FormData or URLSearchParams or USVString)
   if (ObjectPrototypeIsPrototypeOf(ReadableStreamPrototype, V)) {
@@ -501,6 +507,14 @@ webidl.converters["BodyInit_DOMString"] = (V, prefix, context, opts) => {
     if (ArrayBufferIsView(V)) {
       return webidl.converters["ArrayBufferView"](V, prefix, context, opts);
     }
+    if (webidl.isAsyncIterable(V) && !isStringObject(V)) {
+      return webidl.converters["async iterable<Uint8Array>"](
+        V,
+        prefix,
+        context,
+        opts,
+      );
+    }
   }
   // BodyInit conversion is passed to extractBody(), which calls core.encode().
   // core.encode() will UTF-8 encode strings with replacement, being equivalent to the USV normalization.
diff --git a/ext/fetch/lib.deno_fetch.d.ts b/ext/fetch/lib.deno_fetch.d.ts
index d219a3859..8614dec89 100644
--- a/ext/fetch/lib.deno_fetch.d.ts
+++ b/ext/fetch/lib.deno_fetch.d.ts
@@ -163,6 +163,8 @@ type BodyInit =
   | FormData
   | URLSearchParams
   | ReadableStream<Uint8Array>
+  | Iterable<Uint8Array>
+  | AsyncIterable<Uint8Array>
   | string;
 /** @category Fetch */
 type RequestDestination =