Require React 18

CHANGELOG.md

@@ -23,6 +23,14 @@ After a release, please make sure to run `bundle exec rake update_changelog`. Th
 
 Changes since the last non-beta release.
 
+#### Removed
+
+- Support for React 16 and 17. [PR 1710](https://github.com/shakacode/react_on_rails/pull/1710) by [alexeyr-ci](https://github.com/alexeyr-ci).
+
+#### Breaking Changes
+
+- React >=18 is now required.
+
 ### [15.0.0] - 2025-08-28
 
 See [Release Notes](docs/release-notes/15.0.0.md) for full details.

docs/release-notes/16.0.0.md

@@ -0,0 +1,7 @@
+# React on Rails 16.0.0 Release Notes
+
+Also see the Changelog for 16.0.0 (TODO: insert link once released).
+
+## Breaking Changes
+
+- Support for React 16 and 17 is dropped.

node_package/src/ClientSideRenderer.ts

@@ -1,12 +1,12 @@
 /* eslint-disable max-classes-per-file */
 
 import type { ReactElement } from 'react';
-import type { RailsContext, RegisteredComponent, RenderFunction, Root } from './types/index.ts';
+import type { Root } from 'react-dom/client';
+import type { RailsContext, RegisteredComponent, RenderFunction } from './types/index.ts';
 
 import { getRailsContext, resetRailsContext } from './context.ts';
 import createReactOutput from './createReactOutput.ts';
 import { isServerRenderHash } from './isServerRenderResult.ts';
-import { supportsHydrate, supportsRootApi, unmountComponentAtNode } from './reactApis.cts';
 import reactHydrateOrRender from './reactHydrateOrRender.ts';
 import { debugTurbolinks } from './turbolinksUtils.ts';
 import * as StoreRegistry from './StoreRegistry.ts';
@@ -100,8 +100,8 @@ class ComponentRenderer {
           return;
         }
 
-        // Hydrate if available and was server rendered
-        const shouldHydrate = supportsHydrate && !!domNode.innerHTML;
+        // Hydrate if the node was server rendered
+        const shouldHydrate = !!domNode.innerHTML;
 
         const reactElementOrRouterResult = createReactOutput({
           componentObj,
@@ -117,15 +117,12 @@ class ComponentRenderer {
 You returned a server side type of react-router error: ${JSON.stringify(reactElementOrRouterResult)}
 You should return a React.Component always for the client side entry point.`);
         } else {
-          const rootOrElement = reactHydrateOrRender(
+          this.root = reactHydrateOrRender(
             domNode,
             reactElementOrRouterResult as ReactElement,
             shouldHydrate,
           );
           this.state = 'rendered';
-          if (supportsRootApi) {
-            this.root = rootOrElement as Root;
-          }
         }
       }
     } catch (e: unknown) {
@@ -143,27 +140,8 @@ You should return a React.Component always for the client side entry point.`);
     }
     this.state = 'unmounted';
 
-    if (supportsRootApi) {
-      this.root?.unmount();
-      this.root = undefined;
-    } else {
-      const domNode = document.getElementById(this.domNodeId);
-      if (!domNode) {
-        return;
-      }
-
-      try {
-        // eslint-disable-next-line @typescript-eslint/no-deprecated
-        unmountComponentAtNode(domNode);
-      } catch (e: unknown) {
-        const error = e instanceof Error ? e : new Error('Unknown error');
-        console.info(
-          `Caught error calling unmountComponentAtNode: ${error.message} for domNode`,
-          domNode,
-          error,
-        );
-      }
-    }
+    this.root?.unmount();
+    this.root = undefined;
   }
 
   waitUntilRendered(): Promise<void> {

node_package/src/ReactOnRails.client.ts

@@ -1,4 +1,5 @@
 import type { ReactElement } from 'react';
+import type { Root } from 'react-dom/client';
 import * as ClientStartup from './clientStartup.ts';
 import { renderOrHydrateComponent, hydrateStore } from './ClientSideRenderer.ts';
 import * as ComponentRegistry from './ComponentRegistry.ts';
@@ -9,7 +10,6 @@ import * as Authenticity from './Authenticity.ts';
 import type {
   RegisteredComponent,
   RenderResult,
-  RenderReturnType,
   ReactComponentOrRenderFunction,
   AuthenticityHeaders,
   Store,
@@ -64,7 +64,7 @@ globalThis.ReactOnRails = {
     return StoreRegistry.getOrWaitForStoreGenerator(name);
   },
 
-  reactHydrateOrRender(domNode: Element, reactElement: ReactElement, hydrate: boolean): RenderReturnType {
+  reactHydrateOrRender(domNode: Element, reactElement: ReactElement, hydrate: boolean): Root {
     return reactHydrateOrRender(domNode, reactElement, hydrate);
   },
 
@@ -128,7 +128,7 @@ globalThis.ReactOnRails = {
     StoreRegistry.clearHydratedStores();
   },
 
-  render(name: string, props: Record<string, string>, domNodeId: string, hydrate: boolean): RenderReturnType {
+  render(name: string, props: Record<string, string>, domNodeId: string, hydrate: boolean): Root {
     const componentObj = ComponentRegistry.get(name);
     const reactElement = createReactOutput({ componentObj, props, domNodeId });
 

node_package/src/handleError.ts

@@ -1,5 +1,5 @@
 import * as React from 'react';
-import { renderToString } from './ReactDOMServer.cts';
+import { renderToString } from 'react-dom/server';
 import type { ErrorOptions } from './types/index.ts';
 
 function handleRenderFunctionIssue(options: ErrorOptions): string {

node_package/src/reactApis.ts

@@ -0,0 +1,10 @@
+import * as React from 'react';
+
+// eslint-disable-next-line import/prefer-default-export
+export const ensureReactUseAvailable = () => {
+  if (!('use' in React) || typeof React.use !== 'function') {
+    throw new Error(
+      'React.use is not defined. Please ensure you are using React 19 to use server components.',
+    );
+  }
+};

node_package/src/reactHydrateOrRender.ts

@@ -1,11 +1,16 @@
 import type { ReactElement } from 'react';
-import type { RenderReturnType } from './types/index.ts';
-import { reactHydrate, reactRender } from './reactApis.cts';
+import { createRoot, hydrateRoot, Root } from 'react-dom/client';
 
 export default function reactHydrateOrRender(
   domNode: Element,
   reactElement: ReactElement,
   hydrate: boolean,
-): RenderReturnType {
-  return hydrate ? reactHydrate(domNode, reactElement) : reactRender(domNode, reactElement);
+): Root {
+  if (hydrate) {
+    return hydrateRoot(domNode, reactElement);
+  }
+
+  const root = createRoot(domNode);
+  root.render(reactElement);
+  return root;
 }

node_package/src/serverRenderReactComponent.ts

@@ -1,12 +1,12 @@
 import * as React from 'react';
 import type { ReactElement } from 'react';
+import { renderToString } from 'react-dom/server';
 
 import * as ComponentRegistry from './ComponentRegistry.ts';
 import createReactOutput from './createReactOutput.ts';
 import { isPromise, isServerRenderHash } from './isServerRenderResult.ts';
 import buildConsoleReplay from './buildConsoleReplay.ts';
 import handleError from './handleError.ts';
-import { renderToString } from './ReactDOMServer.cts';
 import { createResultObject, convertToError, validateComponent } from './serverRenderUtils.ts';
 import type {
   CreateReactOutputResult,

node_package/src/streamServerRenderedReactComponent.ts

@@ -1,12 +1,12 @@
 import * as React from 'react';
 import { PassThrough, Readable } from 'stream';
+import { renderToPipeableStream } from 'react-dom/server';
 
 import * as ComponentRegistry from './ComponentRegistry.ts';
 import createReactOutput from './createReactOutput.ts';
 import { isPromise, isServerRenderHash } from './isServerRenderResult.ts';
 import buildConsoleReplay from './buildConsoleReplay.ts';
 import handleError from './handleError.ts';
-import { renderToPipeableStream } from './ReactDOMServer.cts';
 import { createResultObject, convertToError, validateComponent } from './serverRenderUtils.ts';
 import {
   assertRailsContextWithServerStreamingCapabilities,

node_package/src/types/index.ts

@@ -1,6 +1,7 @@
 /// <reference types="react/experimental" />
 
-import type { ReactElement, ReactNode, Component, ComponentType } from 'react';
+import type { ReactElement, ComponentType } from 'react';
+import type { Root } from 'react-dom/client';
 import type { PipeableStream } from 'react-dom/server';
 import type { Readable } from 'stream';
 
@@ -258,15 +259,6 @@ export interface RSCPayloadChunk extends RenderResult {
   html: string;
 }
 
-// from react-dom 18
-export interface Root {
-  render(children: ReactNode): void;
-  unmount(): void;
-}
-
-// eslint-disable-next-line @typescript-eslint/no-invalid-void-type -- inherited from React 16/17, can't avoid here
-export type RenderReturnType = void | Element | Component | Root;
-
 export interface ReactOnRailsOptions {
   /** Gives you debugging messages on Turbolinks events. */
   traceTurbolinks?: boolean;
@@ -316,9 +308,9 @@ export interface ReactOnRails {
    * @param domNode
    * @param reactElement
    * @param hydrate if true will perform hydration, if false will render
-   * @returns {Root|ReactComponent|ReactElement|null}
+   * @returns {Root}
    */
-  reactHydrateOrRender(domNode: Element, reactElement: ReactElement, hydrate: boolean): RenderReturnType;
+  reactHydrateOrRender(domNode: Element, reactElement: ReactElement, hydrate: boolean): Root;
   /**
    * Allow directly calling the page loaded script in case the default events that trigger React
    * rendering are not sufficient, such as when loading JavaScript asynchronously with TurboLinks.
@@ -401,11 +393,9 @@ export interface ReactOnRailsInternal extends ReactOnRails {
    * @param props Props to pass to your component
    * @param domNodeId HTML ID of the node the component will be rendered at
    * @param [hydrate=false] Pass truthy to update server rendered HTML. Default is falsy
-   * @returns {Root|ReactComponent|ReactElement} Under React 18+: the created React root
-   *   (see "What is a root?" in https://github.com/reactwg/react-18/discussions/5).
-   *   Under React 16/17: Reference to your component's backing instance or `null` for stateless components.
+   * @returns {Root} The created React root
    */
-  render(name: string, props: Record<string, string>, domNodeId: string, hydrate?: boolean): RenderReturnType;
+  render(name: string, props: Record<string, string>, domNodeId: string, hydrate?: boolean): Root;
   /**
    * Get the component that you registered
    * @returns {name, component, renderFunction, isRenderer}

node_package/src/wrapServerComponentRenderer/client.tsx

@@ -2,7 +2,7 @@ import * as React from 'react';
 import * as ReactDOMClient from 'react-dom/client';
 import { ReactComponentOrRenderFunction, RenderFunction } from '../types/index.ts';
 import isRenderFunction from '../isRenderFunction.ts';
-import { ensureReactUseAvailable } from '../reactApis.cts';
+import { ensureReactUseAvailable } from '../reactApis.ts';
 import { createRSCProvider } from '../RSCProvider.tsx';
 import getReactServerComponent from '../getReactServerComponent.client.ts';
 

package.json

@@ -75,8 +75,8 @@
     "typescript-eslint": "^8.35.0"
   },
   "peerDependencies": {
-    "react": ">= 16",
-    "react-dom": ">= 16",
+    "react": ">= 18",
+    "react-dom": ">= 18",
     "react-on-rails-rsc": "19.0.2"
   },
   "peerDependenciesMeta": {

script/convert

@@ -32,10 +32,10 @@ gsub_file_content("../package.json", %r{"@testing-library/[^"]*": "[^"]*",}, "")
 gsub_file_content("../package.json", /,(\s*})/, "\\1")
 
 # Switch to the oldest supported React version
-gsub_file_content("../package.json", /"react": "[^"]*",/, '"react": "16.14.0",')
-gsub_file_content("../package.json", /"react-dom": "[^"]*",/, '"react-dom": "16.14.0",')
-gsub_file_content("../spec/dummy/package.json", /"react": "[^"]*",/, '"react": "16.14.0",')
-gsub_file_content("../spec/dummy/package.json", /"react-dom": "[^"]*",/, '"react-dom": "16.14.0",')
+gsub_file_content("../package.json", /"react": "[^"]*",/, '"react": "18.0.0",')
+gsub_file_content("../package.json", /"react-dom": "[^"]*",/, '"react-dom": "18.0.0",')
+gsub_file_content("../spec/dummy/package.json", /"react": "[^"]*",/, '"react": "18.0.0",')
+gsub_file_content("../spec/dummy/package.json", /"react-dom": "[^"]*",/, '"react-dom": "18.0.0",')
 gsub_file_content(
   "../package.json",
   "jest node_package/tests",
@@ -46,10 +46,6 @@ gsub_file_content("../tsconfig.json", "react-jsx", "react")
 gsub_file_content("../spec/dummy/babel.config.js", "runtime: 'automatic'", "runtime: 'classic'")
 # https://rescript-lang.org/docs/react/latest/migrate-react#configuration
 gsub_file_content("../spec/dummy/rescript.json", '"version": 4', '"version": 4, "mode": "classic"')
-# Find all files under app-react16 and replace the React 19 versions
-Dir.glob(File.expand_path("../spec/dummy/**/app-react16/**/*.*", __dir__)).each do |file|
-  move(file, file.gsub("-react16", ""))
-end
 
 gsub_file_content("../spec/dummy/config/webpack/commonWebpackConfig.js", /generateWebpackConfig(\(\))?/,
                   "webpackConfig")