Flip the arguments of Blocks and make the query optional

packages/react-client/src/ReactFlightClient.js

@@ -152,7 +152,7 @@ export function reportGlobalError(response: Response, error: Error): void {
 }
 
 function readMaybeChunk<T>(maybeChunk: Chunk<T> | T): T {
-  if ((maybeChunk: any).$$typeof !== CHUNK_TYPE) {
+  if (maybeChunk == null || (maybeChunk: any).$$typeof !== CHUNK_TYPE) {
     // $FlowFixMe
     return maybeChunk;
   }

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

@@ -29,12 +29,15 @@ describe('ReactFlight', () => {
     act = ReactNoop.act;
   });
 
-  function block(query, render) {
+  function block(render, load) {
     return function(...args) {
-      let curriedQuery = () => {
-        return query(...args);
+      if (load === undefined) {
+        return [Symbol.for('react.server.block'), render];
+      }
+      let curriedLoad = () => {
+        return load(...args);
       };
-      return [Symbol.for('react.server.block'), render, curriedQuery];
+      return [Symbol.for('react.server.block'), render, curriedLoad];
     };
   }
 
@@ -70,8 +73,32 @@ describe('ReactFlight', () => {
   });
 
   if (ReactFeatureFlags.enableBlocksAPI) {
-    it('can transfer a Block to the client and render there', () => {
-      function Query(firstName, lastName) {
+    it('can transfer a Block to the client and render there, without data', () => {
+      function User(props, data) {
+        return (
+          <span>
+            {props.greeting} {typeof data}
+          </span>
+        );
+      }
+      let loadUser = block(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 undefined</span>);
+    });
+
+    it('can transfer a Block to the client and render there, with data', () => {
+      function load(firstName, lastName) {
         return {name: firstName + ' ' + lastName};
       }
       function User(props, data) {
@@ -81,7 +108,7 @@ describe('ReactFlight', () => {
           </span>
         );
       }
-      let loadUser = block(Query, User);
+      let loadUser = block(User, load);
       let model = {
         User: loadUser('Seb', 'Smith'),
       };

packages/react-flight-dom-relay/src/__tests__/ReactFlightDOMRelay-test.internal.js

@@ -44,12 +44,15 @@ describe('ReactFlightDOMRelay', () => {
     return model;
   }
 
-  function block(query, render) {
+  function block(render, load) {
     return function(...args) {
-      let curriedQuery = () => {
-        return query(...args);
+      if (load === undefined) {
+        return [Symbol.for('react.server.block'), render];
+      }
+      let curriedLoad = () => {
+        return load(...args);
       };
-      return [Symbol.for('react.server.block'), render, curriedQuery];
+      return [Symbol.for('react.server.block'), render, curriedLoad];
     };
   }
 
@@ -89,7 +92,7 @@ describe('ReactFlightDOMRelay', () => {
   });
 
   it.experimental('can transfer a Block to the client and render there', () => {
-    function Query(firstName, lastName) {
+    function load(firstName, lastName) {
       return {name: firstName + ' ' + lastName};
     }
     function User(props, data) {
@@ -99,7 +102,7 @@ describe('ReactFlightDOMRelay', () => {
         </span>
       );
     }
-    let loadUser = block(Query, User);
+    let loadUser = block(User, load);
     let model = {
       User: loadUser('Seb', 'Smith'),
     };

packages/react-flight-dom-webpack/src/__tests__/ReactFlightDOM-test.js

@@ -62,7 +62,7 @@ describe('ReactFlightDOM', () => {
     };
   }
 
-  function block(query, render) {
+  function block(render, load) {
     let idx = webpackModuleIdx++;
     webpackModules[idx] = {
       d: render,
@@ -73,10 +73,13 @@ describe('ReactFlightDOM', () => {
       name: 'd',
     };
     return function(...args) {
-      let curriedQuery = () => {
-        return query(...args);
+      if (load === undefined) {
+        return [Symbol.for('react.server.block'), render];
+      }
+      let curriedLoad = () => {
+        return load(...args);
       };
-      return [Symbol.for('react.server.block'), 'path/' + idx, curriedQuery];
+      return [Symbol.for('react.server.block'), 'path/' + idx, curriedLoad];
     };
   }
 
@@ -288,7 +291,7 @@ describe('ReactFlightDOM', () => {
           reject(e);
         };
       });
-      function Query() {
+      function load() {
         if (promise) {
           throw promise;
         }
@@ -300,8 +303,8 @@ describe('ReactFlightDOM', () => {
       function DelayedText({children}, data) {
         return <Text>{children}</Text>;
       }
-      let _block = block(Query, DelayedText);
-      return [_block(), _resolve, _reject];
+      let loadBlock = block(DelayedText, load);
+      return [loadBlock(), _resolve, _reject];
     }
 
     const [FriendsModel, resolveFriendsModel] = makeDelayedText();

packages/react-reconciler/src/__tests__/ReactBlocks-test.js

@@ -49,8 +49,30 @@ describe('ReactBlocks', () => {
     };
   });
 
+  it.experimental('renders a simple component', () => {
+    function User(props, data) {
+      return <div>{typeof data}</div>;
+    }
+
+    function App({Component}) {
+      return (
+        <Suspense fallback={'Loading...'}>
+          <Component name="Name" />
+        </Suspense>
+      );
+    }
+
+    let loadUser = block(User);
+
+    ReactNoop.act(() => {
+      ReactNoop.render(<App Component={loadUser()} />);
+    });
+
+    expect(ReactNoop).toMatchRenderedOutput(<div>undefined</div>);
+  });
+
   it.experimental('prints the name of the render function in warnings', () => {
-    function Query(firstName) {
+    function load(firstName) {
       return {
         name: firstName,
       };
@@ -69,7 +91,7 @@ describe('ReactBlocks', () => {
       );
     }
 
-    let loadUser = block(Query, User);
+    let loadUser = block(User, load);
 
     expect(() => {
       ReactNoop.act(() => {
@@ -86,8 +108,8 @@ describe('ReactBlocks', () => {
     );
   });
 
-  it.experimental('renders a component with a suspending query', async () => {
-    function Query(id) {
+  it.experimental('renders a component with a suspending load', async () => {
+    function load(id) {
       return {
         id: id,
         name: readString('Sebastian'),
@@ -102,7 +124,7 @@ describe('ReactBlocks', () => {
       );
     }
 
-    let loadUser = block(Query, Render);
+    let loadUser = block(Render, load);
 
     function App({User}) {
       return (
@@ -128,7 +150,7 @@ describe('ReactBlocks', () => {
   it.experimental(
     'does not support a lazy wrapper around a chunk',
     async () => {
-      function Query(id) {
+      function load(id) {
         return {
           id: id,
           name: readString('Sebastian'),
@@ -143,7 +165,7 @@ describe('ReactBlocks', () => {
         );
       }
 
-      let loadUser = block(Query, Render);
+      let loadUser = block(Render, load);
 
       function App({User}) {
         return (
@@ -187,7 +209,7 @@ describe('ReactBlocks', () => {
   it.experimental(
     'can receive updated data for the same component',
     async () => {
-      function Query(firstName) {
+      function load(firstName) {
         return {
           name: firstName,
         };
@@ -203,7 +225,7 @@ describe('ReactBlocks', () => {
         );
       }
 
-      let loadUser = block(Query, Render);
+      let loadUser = block(Render, load);
 
       function App({User}) {
         return (

packages/react-server/src/ReactFlightServer.js

@@ -191,11 +191,11 @@ export function resolveModelToJSON(
         }
       }
       case '2': {
-        // Query
-        let query: () => ReactModel = (value: any);
+        // Load function
+        let load: () => ReactModel = (value: any);
         try {
-          // Attempt to resolve the query.
-          return query();
+          // Attempt to resolve the data.
+          return load();
         } catch (x) {
           if (
             typeof x === 'object' &&
@@ -204,12 +204,12 @@ export function resolveModelToJSON(
           ) {
             // Something suspended, we'll need to create a new segment and resolve it later.
             request.pendingChunks++;
-            let newSegment = createSegment(request, query);
+            let newSegment = createSegment(request, load);
             let ping = newSegment.ping;
             x.then(ping, ping);
             return serializeIDRef(newSegment.id);
           } else {
-            // This query failed, encode the error as a separate row and reference that.
+            // This load failed, encode the error as a separate row and reference that.
             request.pendingChunks++;
             let errorId = request.nextChunkId++;
             emitErrorChunk(request, errorId, x);

packages/react/src/ReactBlock.js

@@ -16,14 +16,14 @@ import {
   REACT_FORWARD_REF_TYPE,
 } from 'shared/ReactSymbols';
 
-type BlockQueryFunction<Args: Iterable<any>, Data> = (...args: Args) => Data;
+type BlockLoadFunction<Args: Iterable<any>, Data> = (...args: Args) => Data;
 export type BlockRenderFunction<Props, Data> = (
   props: Props,
   data: Data,
 ) => React$Node;
 
 type Payload<Props, Args: Iterable<any>, Data> = {
-  query: BlockQueryFunction<Args, Data>,
+  load: BlockLoadFunction<Args, Data>,
   args: Args,
   render: BlockRenderFunction<Props, Data>,
 };
@@ -44,20 +44,20 @@ function lazyInitializer<Props, Args: Iterable<any>, Data>(
 ): BlockComponent<Props, Data> {
   return {
     $$typeof: REACT_BLOCK_TYPE,
-    _data: payload.query.apply(null, payload.args),
+    _data: payload.load.apply(null, payload.args),
     _render: payload.render,
   };
 }
 
 export function block<Args: Iterable<any>, Props, Data>(
-  query: BlockQueryFunction<Args, Data>,
   render: BlockRenderFunction<Props, Data>,
+  load?: BlockLoadFunction<Args, Data>,
 ): (...args: Args) => Block<Props> {
   if (__DEV__) {
-    if (typeof query !== 'function') {
+    if (load !== undefined && typeof load !== 'function') {
       console.error(
-        'Blocks require a query function but was given %s.',
-        query === null ? 'null' : typeof query,
+        'Blocks require a load function, if provided, but was given %s.',
+        load === null ? 'null' : typeof load,
       );
     }
     if (render != null && render.$$typeof === REACT_MEMO_TYPE) {
@@ -97,11 +97,28 @@ export function block<Args: Iterable<any>, Props, Data>(
     }
   }
 
+  if (load === undefined) {
+    return function(): Block<Props> {
+      let blockComponent: BlockComponent<Props, void> = {
+        $$typeof: REACT_BLOCK_TYPE,
+        _data: undefined,
+        // $FlowFixMe: Data must be void in this scenario.
+        _render: render,
+      };
+
+      // $FlowFixMe
+      return blockComponent;
+    };
+  }
+
+  // Trick to let Flow refine this.
+  let loadFn = load;
+
   return function(): Block<Props> {
     let args: Args = arguments;
 
     let payload: Payload<Props, Args, Data> = {
-      query: query,
+      load: loadFn,
       args: args,
       render: render,
     };