[Flight] Integrate Blocks into Flight (#18371)

* Resolve Server-side Blocks instead of Components

React elements should no longer be used to extract arbitrary data but only
for prerendering trees.

Blocks are used to create asynchronous behavior.

* Resolve Blocks in the Client

* Tests

* Bug fix relay JSON traversal

It's supposed to pass the original object and not the new one.

* Lint

* Move Noop Module Test Helpers to top level entry points

This module has shared state. It needs to be external from builds.

This lets us test the built versions of the Noop renderer.

packages/react-client/src/ReactFlightClient.js

@@ -7,18 +7,25 @@
  * @flow
  */
 
-import {REACT_ELEMENT_TYPE} from 'shared/ReactSymbols';
+import type {BlockComponent, BlockRenderFunction} from 'react/src/ReactBlock';
+import type {LazyComponent} from 'react/src/ReactLazy';
 
-// import type {
-//   ModuleReference,
-//   ModuleMetaData,
-// } from './ReactFlightClientHostConfig';
+import type {
+  ModuleReference,
+  ModuleMetaData,
+} from './ReactFlightClientHostConfig';
 
-// import {
-//   resolveModuleReference,
-//   preloadModule,
-//   requireModule,
-// } from './ReactFlightClientHostConfig';
+import {
+  resolveModuleReference,
+  preloadModule,
+  requireModule,
+} from './ReactFlightClientHostConfig';
+
+import {
+  REACT_LAZY_TYPE,
+  REACT_BLOCK_TYPE,
+  REACT_ELEMENT_TYPE,
+} from 'shared/ReactSymbols';
 
 export type ReactModelRoot<T> = {|
   model: T,
@@ -32,40 +39,43 @@ export type JSONValue =
   | {[key: string]: JSONValue}
   | Array<JSONValue>;
 
-const isArray = Array.isArray;
-
 const PENDING = 0;
 const RESOLVED = 1;
 const ERRORED = 2;
 
+const CHUNK_TYPE = Symbol('flight.chunk');
+
 type PendingChunk = {|
+  $$typeof: Symbol,
   status: 0,
   value: Promise<void>,
   resolve: () => void,
 |};
-type ResolvedChunk = {|
+type ResolvedChunk<T> = {|
+  $$typeof: Symbol,
   status: 1,
-  value: mixed,
+  value: T,
   resolve: null,
 |};
 type ErroredChunk = {|
+  $$typeof: Symbol,
   status: 2,
   value: Error,
   resolve: null,
 |};
-type Chunk = PendingChunk | ResolvedChunk | ErroredChunk;
+type Chunk<T> = PendingChunk | ResolvedChunk<T> | ErroredChunk;
 
 export type Response = {
   partialRow: string,
   modelRoot: ReactModelRoot<any>,
-  chunks: Map<number, Chunk>,
+  chunks: Map<number, Chunk<any>>,
 };
 
 export function createResponse(): Response {
   let modelRoot: ReactModelRoot<any> = ({}: any);
-  let rootChunk: Chunk = createPendingChunk();
+  let rootChunk: Chunk<any> = createPendingChunk();
   definePendingProperty(modelRoot, 'model', rootChunk);
-  let chunks: Map<number, Chunk> = new Map();
+  let chunks: Map<number, Chunk<any>> = new Map();
   chunks.set(0, rootChunk);
   let response = {
     partialRow: '',
@@ -79,6 +89,7 @@ function createPendingChunk(): PendingChunk {
   let resolve: () => void = (null: any);
   let promise = new Promise(r => (resolve = r));
   return {
+    $$typeof: CHUNK_TYPE,
     status: PENDING,
     value: promise,
     resolve: resolve,
@@ -87,13 +98,14 @@ function createPendingChunk(): PendingChunk {
 
 function createErrorChunk(error: Error): ErroredChunk {
   return {
+    $$typeof: CHUNK_TYPE,
     status: ERRORED,
     value: error,
     resolve: null,
   };
 }
 
-function triggerErrorOnChunk(chunk: Chunk, error: Error): void {
+function triggerErrorOnChunk<T>(chunk: Chunk<T>, error: Error): void {
   if (chunk.status !== PENDING) {
     // We already resolved. We didn't expect to see this.
     return;
@@ -106,21 +118,22 @@ function triggerErrorOnChunk(chunk: Chunk, error: Error): void {
   resolve();
 }
 
-function createResolvedChunk(value: mixed): ResolvedChunk {
+function createResolvedChunk<T>(value: T): ResolvedChunk<T> {
   return {
+    $$typeof: CHUNK_TYPE,
     status: RESOLVED,
     value: value,
     resolve: null,
   };
 }
 
-function resolveChunk(chunk: Chunk, value: mixed): void {
+function resolveChunk<T>(chunk: Chunk<T>, value: T): void {
   if (chunk.status !== PENDING) {
     // We already resolved. We didn't expect to see this.
     return;
   }
   let resolve = chunk.resolve;
-  let resolvedChunk: ResolvedChunk = (chunk: any);
+  let resolvedChunk: ResolvedChunk<T> = (chunk: any);
   resolvedChunk.status = RESOLVED;
   resolvedChunk.value = value;
   resolvedChunk.resolve = null;
@@ -138,10 +151,23 @@ export function reportGlobalError(response: Response, error: Error): void {
   });
 }
 
-function definePendingProperty(
+function readMaybeChunk<T>(maybeChunk: Chunk<T> | T): T {
+  if ((maybeChunk: any).$$typeof !== CHUNK_TYPE) {
+    // $FlowFixMe
+    return maybeChunk;
+  }
+  let chunk: Chunk<T> = (maybeChunk: any);
+  if (chunk.status === RESOLVED) {
+    return chunk.value;
+  } else {
+    throw chunk.value;
+  }
+}
+
+function definePendingProperty<T>(
   object: Object,
   key: string,
-  chunk: Chunk,
+  chunk: Chunk<T>,
 ): void {
   Object.defineProperty(object, key, {
     configurable: false,
@@ -197,6 +223,55 @@ function createElement(type, key, props): React$Element<any> {
   return element;
 }
 
+type UninitializedBlockPayload<Data> = [
+  mixed,
+  ModuleMetaData | Chunk<ModuleMetaData>,
+  Data | Chunk<Data>,
+];
+
+type Thenable<T> = {
+  then(resolve: (T) => mixed, reject?: (mixed) => mixed): Thenable<any>,
+};
+
+function initializeBlock<Props, Data>(
+  tuple: UninitializedBlockPayload<Data>,
+): BlockComponent<Props, Data> {
+  // Require module first and then data. The ordering matters.
+  let moduleMetaData: ModuleMetaData = readMaybeChunk(tuple[1]);
+  let moduleReference: ModuleReference<
+    BlockRenderFunction<Props, Data>,
+  > = resolveModuleReference(moduleMetaData);
+  // TODO: Do this earlier, as the chunk is resolved.
+  preloadModule(moduleReference);
+
+  let moduleExport = requireModule(moduleReference);
+
+  // The ordering here is important because this call might suspend.
+  // We don't want that to prevent the module graph for being initialized.
+  let data: Data = readMaybeChunk(tuple[2]);
+
+  return {
+    $$typeof: REACT_BLOCK_TYPE,
+    _status: -1,
+    _data: data,
+    _render: moduleExport,
+  };
+}
+
+function createLazyBlock<Props, Data>(
+  tuple: UninitializedBlockPayload<Data>,
+): LazyComponent<BlockComponent<Props, Data>, UninitializedBlockPayload<Data>> {
+  let lazyType: LazyComponent<
+    BlockComponent<Props, Data>,
+    UninitializedBlockPayload<Data>,
+  > = {
+    $$typeof: REACT_LAZY_TYPE,
+    _payload: tuple,
+    _init: initializeBlock,
+  };
+  return lazyType;
+}
+
 export function parseModelFromJSON(
   response: Response,
   targetObj: Object,
@@ -217,20 +292,26 @@ export function parseModelFromJSON(
         if (!chunk) {
           chunk = createPendingChunk();
           chunks.set(id, chunk);
-        } else if (chunk.status === RESOLVED) {
-          return chunk.value;
         }
-        definePendingProperty(targetObj, key, chunk);
-        return undefined;
+        return chunk;
       }
     }
+    if (value === '@') {
+      return REACT_BLOCK_TYPE;
+    }
   }
-  if (isArray(value)) {
+  if (typeof value === 'object' && value !== null) {
     let tuple: [mixed, mixed, mixed, mixed] = (value: any);
-    if (tuple[0] === REACT_ELEMENT_TYPE) {
-      // TODO: Consider having React just directly accept these arrays as elements.
-      // Or even change the ReactElement type to be an array.
-      return createElement(tuple[1], tuple[2], tuple[3]);
+    switch (tuple[0]) {
+      case REACT_ELEMENT_TYPE: {
+        // TODO: Consider having React just directly accept these arrays as elements.
+        // Or even change the ReactElement type to be an array.
+        return createElement(tuple[1], tuple[2], tuple[3]);
+      }
+      case REACT_BLOCK_TYPE: {
+        // TODO: Consider having React just directly accept these arrays as blocks.
+        return createLazyBlock((tuple: any));
+      }
     }
   }
   return value;

packages/react-client/src/__tests__/ReactFlight-test.js

@@ -10,7 +10,11 @@
 
 'use strict';
 
+const ReactFeatureFlags = require('shared/ReactFeatureFlags');
+
+let act;
 let React;
+let ReactNoop;
 let ReactNoopFlightServer;
 let ReactNoopFlightClient;
 
@@ -19,24 +23,78 @@ describe('ReactFlight', () => {
     jest.resetModules();
 
     React = require('react');
+    ReactNoop = require('react-noop-renderer');
     ReactNoopFlightServer = require('react-noop-renderer/flight-server');
     ReactNoopFlightClient = require('react-noop-renderer/flight-client');
+    act = ReactNoop.act;
   });
 
-  it('can resolve a model', () => {
+  function block(query, render) {
+    return function(...args) {
+      let curriedQuery = () => {
+        return query(...args);
+      };
+      return [Symbol.for('react.server.block'), render, curriedQuery];
+    };
+  }
+
+  it('can render a server component', () => {
     function Bar({text}) {
       return text.toUpperCase();
     }
     function Foo() {
       return {
-        bar: [<Bar text="a" />, <Bar text="b" />],
+        bar: (
+          <div>
+            <Bar text="a" />, <Bar text="b" />
+          </div>
+        ),
       };
     }
     let transport = ReactNoopFlightServer.render({
       foo: <Foo />,
     });
     let root = ReactNoopFlightClient.read(transport);
     let model = root.model;
-    expect(model).toEqual({foo: {bar: ['A', 'B']}});
+    expect(model).toEqual({
+      foo: {
+        bar: (
+          <div>
+            {'A'}
+            {', '}
+            {'B'}
+          </div>
+        ),
+      },
+    });
   });
+
+  if (ReactFeatureFlags.enableBlocksAPI) {
+    it('can transfer a Block to the client and render there', () => {
+      function Query(firstName, lastName) {
+        return {name: firstName + ' ' + lastName};
+      }
+      function User(props, data) {
+        return (
+          <span>
+            {props.greeting}, {data.name}
+          </span>
+        );
+      }
+      let loadUser = block(Query, User);
+      let model = {
+        User: loadUser('Seb', 'Smith'),
+      };
+
+      let transport = ReactNoopFlightServer.render(model);
+      let root = ReactNoopFlightClient.read(transport);
+
+      act(() => {
+        let UserClient = root.model.User;
+        ReactNoop.render(<UserClient greeting="Hello" />);
+      });
+
+      expect(ReactNoop).toMatchRenderedOutput(<span>Hello, Seb Smith</span>);
+    });
+  }
 });