Adds experimental fundamental interface

package.json

@@ -104,6 +104,7 @@
     "debug-test": "cross-env NODE_ENV=development node --inspect-brk node_modules/.bin/jest --config ./scripts/jest/config.source.js --runInBand",
     "test": "cross-env NODE_ENV=development jest --config ./scripts/jest/config.source.js",
     "test-persistent": "cross-env NODE_ENV=development jest --config ./scripts/jest/config.source-persistent.js",
+    "debug-test-persistent": "cross-env NODE_ENV=development node --inspect-brk node_modules/.bin/jest --config ./scripts/jest/config.source-persistent.js --runInBand",
     "test-prod": "cross-env NODE_ENV=production jest --config ./scripts/jest/config.source.js",
     "test-prod-build": "yarn test-build-prod",
     "test-build": "cross-env NODE_ENV=development jest --config ./scripts/jest/config.build.js",

packages/react-art/src/ReactARTHostConfig.js

@@ -444,3 +444,23 @@ export function unmountEventComponent(
 ): void {
   throw new Error('Not yet implemented.');
 }
+
+export function getFundamentalComponentInstance(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function mountFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function shouldUpdateFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function updateFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function unmountFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}

packages/react-dom/src/client/ReactDOMHostConfig.js

@@ -45,6 +45,7 @@ import type {DOMContainer} from './ReactDOM';
 import type {
   ReactDOMEventResponder,
   ReactDOMEventComponentInstance,
+  ReactDOMFundamentalComponentInstance,
 } from 'shared/ReactDOMTypes';
 import {
   addRootEventTypesForComponentInstance,
@@ -103,6 +104,7 @@ export type NoTimeout = -1;
 import {
   enableSuspenseServerRenderer,
   enableFlareAPI,
+  enableFundamentalAPI,
 } from 'shared/ReactFeatureFlags';
 import warning from 'shared/warning';
 
@@ -882,3 +884,65 @@ export function unmountEventComponent(
     unmountEventResponder(eventComponentInstance);
   }
 }
+
+export function getFundamentalComponentInstance(
+  fundamentalInstance: ReactDOMFundamentalComponentInstance,
+): Instance {
+  if (enableFundamentalAPI) {
+    const {currentFiber, impl, props, state} = fundamentalInstance;
+    const instance = impl.getInstance(null, props, state);
+    precacheFiberNode(currentFiber, instance);
+    return instance;
+  }
+  // Because of the flag above, this gets around the Flow error;
+  return (null: any);
+}
+
+export function mountFundamentalComponent(
+  fundamentalInstance: ReactDOMFundamentalComponentInstance,
+): void {
+  if (enableFundamentalAPI) {
+    const {impl, instance, props, state} = fundamentalInstance;
+    const onMount = impl.onMount;
+    if (onMount !== undefined) {
+      onMount(null, instance, props, state);
+    }
+  }
+}
+
+export function shouldUpdateFundamentalComponent(
+  fundamentalInstance: ReactDOMFundamentalComponentInstance,
+): boolean {
+  if (enableFundamentalAPI) {
+    const {impl, prevProps, props, state} = fundamentalInstance;
+    const shouldUpdate = impl.shouldUpdate;
+    if (shouldUpdate !== undefined) {
+      return shouldUpdate(null, prevProps, props, state);
+    }
+  }
+  return true;
+}
+
+export function updateFundamentalComponent(
+  fundamentalInstance: ReactDOMFundamentalComponentInstance,
+): void {
+  if (enableFundamentalAPI) {
+    const {impl, instance, prevProps, props, state} = fundamentalInstance;
+    const onUpdate = impl.onUpdate;
+    if (onUpdate !== undefined) {
+      onUpdate(null, instance, prevProps, props, state);
+    }
+  }
+}
+
+export function unmountFundamentalComponent(
+  fundamentalInstance: ReactDOMFundamentalComponentInstance,
+): void {
+  if (enableFundamentalAPI) {
+    const {impl, instance, props, state} = fundamentalInstance;
+    const onUnmount = impl.onUnmount;
+    if (onUnmount !== undefined) {
+      onUnmount(null, instance, props, state);
+    }
+  }
+}

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

@@ -23,6 +23,7 @@ import {
   warnAboutDeprecatedLifecycles,
   enableSuspenseServerRenderer,
   enableFlareAPI,
+  enableFundamentalAPI,
 } from 'shared/ReactFeatureFlags';
 
 import {
@@ -39,6 +40,7 @@ import {
   REACT_LAZY_TYPE,
   REACT_MEMO_TYPE,
   REACT_EVENT_COMPONENT_TYPE,
+  REACT_FUNDAMENTAL_TYPE,
 } from 'shared/ReactSymbols';
 
 import {
@@ -1190,6 +1192,43 @@ class ReactDOMServerRenderer {
             );
           }
           // eslint-disable-next-line-no-fallthrough
+          case REACT_FUNDAMENTAL_TYPE: {
+            if (enableFundamentalAPI) {
+              const fundamentalImpl = elementType.impl;
+              const open = fundamentalImpl.getServerSideString(
+                null,
+                nextElement.props,
+              );
+              const getServerSideStringClose =
+                fundamentalImpl.getServerSideStringClose;
+              const close =
+                getServerSideStringClose !== undefined
+                  ? getServerSideStringClose(null, nextElement.props)
+                  : '';
+              const nextChildren =
+                fundamentalImpl.reconcileChildren !== false
+                  ? toArray(((nextChild: any): ReactElement).props.children)
+                  : [];
+              const frame: Frame = {
+                type: null,
+                domNamespace: parentNamespace,
+                children: nextChildren,
+                childIndex: 0,
+                context: context,
+                footer: close,
+              };
+              if (__DEV__) {
+                ((frame: any): FrameDev).debugElementStack = [];
+              }
+              this.stack.push(frame);
+              return open;
+            }
+            invariant(
+              false,
+              'ReactDOMServer does not yet support the fundamental API.',
+            );
+          }
+          // eslint-disable-next-line-no-fallthrough
           case REACT_LAZY_TYPE:
             invariant(
               false,

packages/react-native-renderer/src/ReactFabricHostConfig.js

@@ -472,3 +472,27 @@ export function unmountEventComponent(
     unmountEventResponder(eventComponentInstance);
   }
 }
+
+export function getFundamentalComponentInstance(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function mountFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function shouldUpdateFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function updateFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function unmountFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function cloneFundamentalInstance(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}

packages/react-native-renderer/src/ReactNativeHostConfig.js

@@ -511,3 +511,23 @@ export function unmountEventComponent(
 ): void {
   throw new Error('Not yet implemented.');
 }
+
+export function getFundamentalComponentInstance(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function mountFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function shouldUpdateFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function updateFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}
+
+export function unmountFundamentalComponent(fundamentalInstance) {
+  throw new Error('Not yet implemented.');
+}

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

@@ -407,6 +407,57 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     unmountEventComponent(): void {
       // NO-OP
     },
+
+    getFundamentalComponentInstance(fundamentalInstance): Instance {
+      const {impl, props, state} = fundamentalInstance;
+      return impl.getInstance(null, props, state);
+    },
+
+    mountFundamentalComponent(fundamentalInstance): void {
+      const {impl, instance, props, state} = fundamentalInstance;
+      const onMount = impl.onUpdate;
+      if (onMount !== undefined) {
+        onMount(null, instance, props, state);
+      }
+    },
+
+    shouldUpdateFundamentalComponent(fundamentalInstance): boolean {
+      const {impl, instance, prevProps, props, state} = fundamentalInstance;
+      const shouldUpdate = impl.shouldUpdate;
+      if (shouldUpdate !== undefined) {
+        return shouldUpdate(null, instance, prevProps, props, state);
+      }
+      return true;
+    },
+
+    updateFundamentalComponent(fundamentalInstance): void {
+      const {impl, instance, prevProps, props, state} = fundamentalInstance;
+      const onUpdate = impl.onUpdate;
+      if (onUpdate !== undefined) {
+        onUpdate(null, instance, prevProps, props, state);
+      }
+    },
+
+    unmountFundamentalComponent(fundamentalInstance): void {
+      const {impl, instance, props, state} = fundamentalInstance;
+      const onUnmount = impl.onUnmount;
+      if (onUnmount !== undefined) {
+        onUnmount(null, instance, props, state);
+      }
+    },
+
+    cloneFundamentalInstance(fundamentalInstance): Instance {
+      const instance = fundamentalInstance.instance;
+      return {
+        children: [],
+        text: instance.text,
+        type: instance.type,
+        prop: instance.prop,
+        id: instance.id,
+        context: instance.context,
+        hidden: instance.hidden,
+      };
+    },
   };
 
   const hostConfig = useMutation

packages/react-reconciler/src/ReactFiber.js

@@ -13,6 +13,7 @@ import type {
   ReactPortal,
   RefObject,
   ReactEventComponent,
+  ReactFundamentalComponent,
 } from 'shared/ReactTypes';
 import type {RootTag} from 'shared/ReactRootTags';
 import type {WorkTag} from 'shared/ReactWorkTags';
@@ -26,7 +27,11 @@ import type {ReactEventComponentInstance} from 'shared/ReactTypes';
 
 import invariant from 'shared/invariant';
 import warningWithoutStack from 'shared/warningWithoutStack';
-import {enableProfilerTimer, enableFlareAPI} from 'shared/ReactFeatureFlags';
+import {
+  enableProfilerTimer,
+  enableFlareAPI,
+  enableFundamentalAPI,
+} from 'shared/ReactFeatureFlags';
 import {NoEffect, Placement} from 'shared/ReactSideEffectTags';
 import {ConcurrentRoot, BatchedRoot} from 'shared/ReactRootTags';
 import {
@@ -49,6 +54,7 @@ import {
   SimpleMemoComponent,
   LazyComponent,
   EventComponent,
+  FundamentalComponent,
 } from 'shared/ReactWorkTags';
 import getComponentName from 'shared/getComponentName';
 
@@ -79,6 +85,7 @@ import {
   REACT_MEMO_TYPE,
   REACT_LAZY_TYPE,
   REACT_EVENT_COMPONENT_TYPE,
+  REACT_FUNDAMENTAL_TYPE,
 } from 'shared/ReactSymbols';
 
 let hasBadMapPolyfill;
@@ -663,6 +670,17 @@ export function createFiberFromTypeAndProps(
                 );
               }
               break;
+            case REACT_FUNDAMENTAL_TYPE:
+              if (enableFundamentalAPI) {
+                return createFiberFromFundamental(
+                  type,
+                  pendingProps,
+                  mode,
+                  expirationTime,
+                  key,
+                );
+              }
+              break;
           }
         }
         let info = '';
@@ -742,7 +760,7 @@ export function createFiberFromFragment(
 }
 
 export function createFiberFromEventComponent(
-  eventComponent: ReactEventComponent<any>,
+  eventComponent: ReactEventComponent<any, any, any>,
   pendingProps: any,
   mode: TypeOfMode,
   expirationTime: ExpirationTime,
@@ -755,6 +773,20 @@ export function createFiberFromEventComponent(
   return fiber;
 }
 
+export function createFiberFromFundamental(
+  fundamentalComponent: ReactFundamentalComponent<any, any>,
+  pendingProps: any,
+  mode: TypeOfMode,
+  expirationTime: ExpirationTime,
+  key: null | string,
+): Fiber {
+  const fiber = createFiber(FundamentalComponent, pendingProps, key, mode);
+  fiber.elementType = fundamentalComponent;
+  fiber.type = fundamentalComponent;
+  fiber.expirationTime = expirationTime;
+  return fiber;
+}
+
 function createFiberFromProfiler(
   pendingProps: any,
   mode: TypeOfMode,