[Fizz] Add FormatContext and Refactor Work (facebook#21103)

* Add format context

* Let the Work node hold all working state for the recursive loop

Stacks are nice and all but there's a cost to maintaining each frame
both in terms of stack size usage and writing to it.

* Move current format context into work

* Synchronously render children of a Suspense boundary

We don't have to spawn work and snapshot the context. Instead we can try
to render the boundary immediately in case it works.

* Lazily create the fallback work

Instead of eagerly create the fallback work and then immediately abort it.
We can just avoid creating it if we finish synchronously.

packages/react-dom/src/server/ReactDOMFizzServerBrowser.js

@@ -16,7 +16,10 @@ import {
   abort,
 } from 'react-server/src/ReactFizzServer';
 
-import {createResponseState} from './ReactDOMServerFormatConfig';
+import {
+  createResponseState,
+  createRootFormatContext,
+} from './ReactDOMServerFormatConfig';
 
 type Options = {
   identifierPrefix?: string,
@@ -46,6 +49,7 @@ function renderToReadableStream(
         children,
         controller,
         createResponseState(options ? options.identifierPrefix : undefined),
+        createRootFormatContext(), // We call this here in case we need options to initialize it.
         options ? options.progressiveChunkSize : undefined,
         options ? options.onError : undefined,
         options ? options.onCompleteAll : undefined,

packages/react-dom/src/server/ReactDOMFizzServerNode.js

@@ -17,7 +17,10 @@ import {
   abort,
 } from 'react-server/src/ReactFizzServer';
 
-import {createResponseState} from './ReactDOMServerFormatConfig';
+import {
+  createResponseState,
+  createRootFormatContext,
+} from './ReactDOMServerFormatConfig';
 
 function createDrainHandler(destination, request) {
   return () => startFlowing(request);
@@ -46,6 +49,7 @@ function pipeToNodeWritable(
     children,
     destination,
     createResponseState(options ? options.identifierPrefix : undefined),
+    createRootFormatContext(), // We call this here in case we need options to initialize it.
     options ? options.progressiveChunkSize : undefined,
     options ? options.onError : undefined,
     options ? options.onCompleteAll : undefined,

packages/react-dom/src/server/ReactDOMServerFormatConfig.js

@@ -22,7 +22,7 @@ import {
 import escapeTextForBrowser from './escapeTextForBrowser';
 import invariant from 'shared/invariant';
 
-// Per response,
+// Per response, global state that is not contextual to the rendering subtree.
 export type ResponseState = {
   placeholderPrefix: PrecomputedChunk,
   segmentPrefix: PrecomputedChunk,
@@ -50,6 +50,56 @@ export function createResponseState(
   };
 }
 
+// Constants for the namespace we use. We don't actually provide the namespace but conditionally
+// use different segment parents based on namespace. Therefore we use constants instead of the string.
+const ROOT_NAMESPACE = 0; // At the root we don't need to know which namespace it is. We just need to know that it's already the right one.
+const HTML_NAMESPACE = 1;
+const SVG_NAMESPACE = 2;
+const MATHML_NAMESPACE = 3;
+
+type NamespaceFlag = 0 | 1 | 2 | 3;
+
+// Lets us keep track of contextual state and pick it back up after suspending.
+export type FormatContext = {
+  namespace: NamespaceFlag, // root/svg/html/mathml
+  selectedValue: null | string, // the selected value(s) inside a <select>, or null outside <select>
+};
+
+function createFormatContext(
+  namespace: NamespaceFlag,
+  selectedValue: null | string,
+): FormatContext {
+  return {
+    namespace,
+    selectedValue,
+  };
+}
+
+export function createRootFormatContext(): FormatContext {
+  return createFormatContext(ROOT_NAMESPACE, null);
+}
+
+export function getChildFormatContext(
+  parentContext: FormatContext,
+  type: string,
+  props: Object,
+): FormatContext {
+  switch (type) {
+    case 'select':
+      return createFormatContext(
+        parentContext.namespace,
+        props.value != null ? props.value : props.defaultValue,
+      );
+    case 'svg':
+      return createFormatContext(SVG_NAMESPACE, null);
+    case 'math':
+      return createFormatContext(MATHML_NAMESPACE, null);
+    case 'foreignObject':
+      return createFormatContext(HTML_NAMESPACE, null);
+  }
+  return parentContext;
+}
+
 // This object is used to lazily reuse the ID of the first generated node, or assign one.
 // We can't assign an ID up front because the node we're attaching it to might already
 // have one. So we need to lazily use that if it's available.

packages/react-native-renderer/src/server/ReactNativeServerFormatConfig.js

@@ -66,6 +66,33 @@ export function createResponseState(): ResponseState {
   };
 }
 
+// isInAParentText
+export type FormatContext = boolean;
+
+export function createRootFormatContext(): FormatContext {
+  return false;
+}
+
+export function getChildFormatContext(
+  parentContext: FormatContext,
+  type: string,
+  props: Object,
+): FormatContext {
+  const prevIsInAParentText = parentContext;
+  const isInAParentText =
+    type === 'AndroidTextInput' || // Android
+    type === 'RCTMultilineTextInputView' || // iOS
+    type === 'RCTSinglelineTextInputView' || // iOS
+    type === 'RCTText' ||
+    type === 'RCTVirtualText';
+
+  if (prevIsInAParentText !== isInAParentText) {
+    return isInAParentText;
+  } else {
+    return parentContext;
+  }
+}
+
 // This object is used to lazily reuse the ID of the first generated node, or assign one.
 // This is very specific to DOM where we can't assign an ID to.
 export type SuspenseBoundaryID = number;

packages/react-noop-renderer/src/ReactNoopServer.js

@@ -82,6 +82,10 @@ const ReactNoopServer = ReactFizzServer({
     return {state: 'pending', children: []};
   },
 
+  getChildFormatContext(): null {
+    return null;
+  },
+
   pushTextInstance(target: Array<Uint8Array>, text: string): void {
     const textInstance: TextInstance = {
       text,
@@ -236,6 +240,7 @@ function render(children: React$Element<any>, options?: Options): Destination {
     children,
     destination,
     null,
+    null,
     options ? options.progressiveChunkSize : undefined,
     options ? options.onError : undefined,
     options ? options.onCompleteAll : undefined,