[Flight] Support streaming of decodeReply in Edge environments (#31852)

We support streaming `multipart/form-data` in Node.js using Busboy since
that's kind of the idiomatic ecosystem way for handling these stream
there. There's not really anything idiomatic like that for Edge that's
universal yet.

This adds a version that's basically just
`AsyncIterable.from(formData)`. It could also be a `ReadableStream` of
those entries since those are also `AsyncIterable`.

I imagine that in the future we might add one from a binary
`ReadableStream` that does the parsing built-in.

packages/react-server-dom-parcel/npm/server.edge.js

@@ -9,6 +9,7 @@ if (process.env.NODE_ENV === 'production') {
 
 exports.renderToReadableStream = s.renderToReadableStream;
 exports.decodeReply = s.decodeReply;
+exports.decodeReplyFromAsyncIterable = s.decodeReplyFromAsyncIterable;
 exports.decodeAction = s.decodeAction;
 exports.decodeFormState = s.decodeFormState;
 exports.createClientReference = s.createClientReference;

packages/react-server-dom-parcel/server.edge.js

@@ -10,6 +10,7 @@
 export {
   renderToReadableStream,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
   createClientReference,

packages/react-server-dom-parcel/src/server/ReactFlightDOMServerEdge.js

@@ -17,6 +17,8 @@ import {
   type ServerReferenceId,
 } from '../client/ReactFlightClientConfigBundlerParcel';
 
+import {ASYNC_ITERATOR} from 'shared/ReactSymbols';
+
 import {
   createRequest,
   createPrerenderRequest,
@@ -30,6 +32,9 @@ import {
   createResponse,
   close,
   getRoot,
+  reportGlobalError,
+  resolveField,
+  resolveFile,
 } from 'react-server/src/ReactFlightReplyServer';
 
 import {
@@ -189,6 +194,50 @@ export function decodeReply<T>(
   return root;
 }
 
+export function decodeReplyFromAsyncIterable<T>(
+  iterable: AsyncIterable<[string, string | File]>,
+  options?: {temporaryReferences?: TemporaryReferenceSet},
+): Thenable<T> {
+  const iterator: AsyncIterator<[string, string | File]> =
+    iterable[ASYNC_ITERATOR]();
+
+  const response = createResponse(
+    serverManifest,
+    '',
+    options ? options.temporaryReferences : undefined,
+  );
+
+  function progress(
+    entry:
+      | {done: false, +value: [string, string | File], ...}
+      | {done: true, +value: void, ...},
+  ) {
+    if (entry.done) {
+      close(response);
+    } else {
+      const [name, value] = entry.value;
+      if (typeof value === 'string') {
+        resolveField(response, name, value);
+      } else {
+        resolveFile(response, name, value);
+      }
+      iterator.next().then(progress, error);
+    }
+  }
+  function error(reason: Error) {
+    reportGlobalError(response, reason);
+    if (typeof (iterator: any).throw === 'function') {
+      // The iterator protocol doesn't necessarily include this but a generator do.
+      // $FlowFixMe should be able to pass mixed
+      iterator.throw(reason).then(error, error);
+    }
+  }
+
+  iterator.next().then(progress, error);
+
+  return getRoot(response);
+}
+
 export function decodeAction<T>(body: FormData): Promise<() => T> | null {
   return decodeActionImpl(body, serverManifest);
 }

packages/react-server-dom-parcel/src/server/react-flight-dom-server.edge.js

@@ -11,6 +11,7 @@ export {
   renderToReadableStream,
   prerender as unstable_prerender,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
   createClientReference,

packages/react-server-dom-turbopack/npm/server.edge.js

@@ -9,6 +9,7 @@ if (process.env.NODE_ENV === 'production') {
 
 exports.renderToReadableStream = s.renderToReadableStream;
 exports.decodeReply = s.decodeReply;
+exports.decodeReplyFromAsyncIterable = s.decodeReplyFromAsyncIterable;
 exports.decodeAction = s.decodeAction;
 exports.decodeFormState = s.decodeFormState;
 exports.registerServerReference = s.registerServerReference;

packages/react-server-dom-turbopack/server.edge.js

@@ -10,6 +10,7 @@
 export {
   renderToReadableStream,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
   registerServerReference,

packages/react-server-dom-turbopack/src/server/ReactFlightDOMServerEdge.js

@@ -12,6 +12,8 @@ import type {Thenable} from 'shared/ReactTypes';
 import type {ClientManifest} from './ReactFlightServerConfigTurbopackBundler';
 import type {ServerManifest} from 'react-client/src/ReactFlightClientConfig';
 
+import {ASYNC_ITERATOR} from 'shared/ReactSymbols';
+
 import {
   createRequest,
   createPrerenderRequest,
@@ -25,6 +27,9 @@ import {
   createResponse,
   close,
   getRoot,
+  reportGlobalError,
+  resolveField,
+  resolveFile,
 } from 'react-server/src/ReactFlightReplyServer';
 
 import {
@@ -183,10 +188,56 @@ function decodeReply<T>(
   return root;
 }
 
+function decodeReplyFromAsyncIterable<T>(
+  iterable: AsyncIterable<[string, string | File]>,
+  turbopackMap: ServerManifest,
+  options?: {temporaryReferences?: TemporaryReferenceSet},
+): Thenable<T> {
+  const iterator: AsyncIterator<[string, string | File]> =
+    iterable[ASYNC_ITERATOR]();
+
+  const response = createResponse(
+    turbopackMap,
+    '',
+    options ? options.temporaryReferences : undefined,
+  );
+
+  function progress(
+    entry:
+      | {done: false, +value: [string, string | File], ...}
+      | {done: true, +value: void, ...},
+  ) {
+    if (entry.done) {
+      close(response);
+    } else {
+      const [name, value] = entry.value;
+      if (typeof value === 'string') {
+        resolveField(response, name, value);
+      } else {
+        resolveFile(response, name, value);
+      }
+      iterator.next().then(progress, error);
+    }
+  }
+  function error(reason: Error) {
+    reportGlobalError(response, reason);
+    if (typeof (iterator: any).throw === 'function') {
+      // The iterator protocol doesn't necessarily include this but a generator do.
+      // $FlowFixMe should be able to pass mixed
+      iterator.throw(reason).then(error, error);
+    }
+  }
+
+  iterator.next().then(progress, error);
+
+  return getRoot(response);
+}
+
 export {
   renderToReadableStream,
   prerender,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
 };

packages/react-server-dom-turbopack/src/server/react-flight-dom-server.edge.js

@@ -11,6 +11,7 @@ export {
   renderToReadableStream,
   prerender as unstable_prerender,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
   registerServerReference,

packages/react-server-dom-webpack/npm/server.edge.js

@@ -9,6 +9,7 @@ if (process.env.NODE_ENV === 'production') {
 
 exports.renderToReadableStream = s.renderToReadableStream;
 exports.decodeReply = s.decodeReply;
+exports.decodeReplyFromAsyncIterable = s.decodeReplyFromAsyncIterable;
 exports.decodeAction = s.decodeAction;
 exports.decodeFormState = s.decodeFormState;
 exports.registerServerReference = s.registerServerReference;

packages/react-server-dom-webpack/server.edge.js

@@ -10,6 +10,7 @@
 export {
   renderToReadableStream,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
   registerServerReference,

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMReplyEdge-test.js

@@ -272,4 +272,40 @@ describe('ReactFlightDOMReplyEdge', () => {
     expect(error).not.toBe(null);
     expect(error.message).toBe('Connection closed.');
   });
+
+  it('can stream the decoding using an async iterable', async () => {
+    let resolve;
+    const promise = new Promise(r => (resolve = r));
+
+    const buffer = new Uint8Array([
+      123, 4, 10, 5, 100, 255, 244, 45, 56, 67, 43, 124, 67, 89, 100, 20,
+    ]);
+
+    const formData = await ReactServerDOMClient.encodeReply({
+      a: Promise.resolve('hello'),
+      b: Promise.resolve(buffer),
+    });
+
+    const iterable = {
+      async *[Symbol.asyncIterator]() {
+        // eslint-disable-next-line no-for-of-loops/no-for-of-loops
+        for (const entry of formData) {
+          yield entry;
+          await promise;
+        }
+      },
+    };
+
+    const decoded = await ReactServerDOMServer.decodeReplyFromAsyncIterable(
+      iterable,
+      webpackServerMap,
+    );
+
+    expect(Object.keys(decoded)).toEqual(['a', 'b']);
+
+    await resolve();
+
+    expect(await decoded.a).toBe('hello');
+    expect(Array.from(await decoded.b)).toEqual(Array.from(buffer));
+  });
 });

packages/react-server-dom-webpack/src/server/ReactFlightDOMServerEdge.js

@@ -12,6 +12,8 @@ import type {Thenable} from 'shared/ReactTypes';
 import type {ClientManifest} from './ReactFlightServerConfigWebpackBundler';
 import type {ServerManifest} from 'react-client/src/ReactFlightClientConfig';
 
+import {ASYNC_ITERATOR} from 'shared/ReactSymbols';
+
 import {
   createRequest,
   createPrerenderRequest,
@@ -25,6 +27,9 @@ import {
   createResponse,
   close,
   getRoot,
+  reportGlobalError,
+  resolveField,
+  resolveFile,
 } from 'react-server/src/ReactFlightReplyServer';
 
 import {
@@ -183,10 +188,56 @@ function decodeReply<T>(
   return root;
 }
 
+function decodeReplyFromAsyncIterable<T>(
+  iterable: AsyncIterable<[string, string | File]>,
+  webpackMap: ServerManifest,
+  options?: {temporaryReferences?: TemporaryReferenceSet},
+): Thenable<T> {
+  const iterator: AsyncIterator<[string, string | File]> =
+    iterable[ASYNC_ITERATOR]();
+
+  const response = createResponse(
+    webpackMap,
+    '',
+    options ? options.temporaryReferences : undefined,
+  );
+
+  function progress(
+    entry:
+      | {done: false, +value: [string, string | File], ...}
+      | {done: true, +value: void, ...},
+  ) {
+    if (entry.done) {
+      close(response);
+    } else {
+      const [name, value] = entry.value;
+      if (typeof value === 'string') {
+        resolveField(response, name, value);
+      } else {
+        resolveFile(response, name, value);
+      }
+      iterator.next().then(progress, error);
+    }
+  }
+  function error(reason: Error) {
+    reportGlobalError(response, reason);
+    if (typeof (iterator: any).throw === 'function') {
+      // The iterator protocol doesn't necessarily include this but a generator do.
+      // $FlowFixMe should be able to pass mixed
+      iterator.throw(reason).then(error, error);
+    }
+  }
+
+  iterator.next().then(progress, error);
+
+  return getRoot(response);
+}
+
 export {
   renderToReadableStream,
   prerender,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
 };

packages/react-server-dom-webpack/src/server/react-flight-dom-server.edge.js

@@ -11,6 +11,7 @@ export {
   renderToReadableStream,
   prerender as unstable_prerender,
   decodeReply,
+  decodeReplyFromAsyncIterable,
   decodeAction,
   decodeFormState,
   registerServerReference,