Remove support for legacy root

src/__tests__/render.js

@@ -212,29 +212,4 @@ describe('render API', () => {
 
     expect(wrapperComponentMountEffect).toHaveBeenCalledTimes(1)
   })
-
-  test('legacyRoot uses legacy ReactDOM.render', () => {
-    expect(() => {
-      render(<div />, {legacyRoot: true})
-    }).toErrorDev(
-      [
-        "Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot",
-      ],
-      {withoutStack: true},
-    )
-  })
-
-  test('legacyRoot uses legacy ReactDOM.hydrate', () => {
-    const ui = <div />
-    const container = document.createElement('div')
-    container.innerHTML = ReactDOMServer.renderToString(ui)
-    expect(() => {
-      render(ui, {container, hydrate: true, legacyRoot: true})
-    }).toErrorDev(
-      [
-        "Warning: ReactDOM.hydrate is no longer supported in React 18. Use hydrateRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot",
-      ],
-      {withoutStack: true},
-    )
-  })
 })

src/pure.js

@@ -1,5 +1,4 @@
 import * as React from 'react'
-import ReactDOM from 'react-dom'
 import * as ReactDOMClient from 'react-dom/client'
 import {
   getQueriesForElement,
@@ -73,7 +72,7 @@ configureDTL({
  */
 const mountedContainers = new Set()
 /**
- * @type Array<{container: import('react-dom').Container, root: ReturnType<typeof createConcurrentRoot>}>
+ * @type Array<{container: import('react-dom').Container, root: ReturnType<typeof createTestRoot>}>
  */
 const mountedRootEntries = []
 
@@ -89,73 +88,10 @@ function wrapUiIfNeeded(innerElement, wrapperComponent) {
     : innerElement
 }
 
-function createConcurrentRoot(
-  container,
-  {hydrate, ui, wrapper: WrapperComponent},
-) {
-  let root
-  if (hydrate) {
-    act(() => {
-      root = ReactDOMClient.hydrateRoot(
-        container,
-        strictModeIfNeeded(wrapUiIfNeeded(ui, WrapperComponent)),
-      )
-    })
-  } else {
-    root = ReactDOMClient.createRoot(container)
-  }
-
-  return {
-    hydrate() {
-      /* istanbul ignore if */
-      if (!hydrate) {
-        throw new Error(
-          'Attempted to hydrate a non-hydrateable root. This is a bug in `@testing-library/react`.',
-        )
-      }
-      // Nothing to do since hydration happens when creating the root object.
-    },
-    render(element) {
-      root.render(element)
-    },
-    unmount() {
-      root.unmount()
-    },
-  }
-}
-
-function createLegacyRoot(container) {
-  return {
-    hydrate(element) {
-      ReactDOM.hydrate(element, container)
-    },
-    render(element) {
-      ReactDOM.render(element, container)
-    },
-    unmount() {
-      ReactDOM.unmountComponentAtNode(container)
-    },
-  }
-}
-
-function renderRoot(
+function createTestView(
   ui,
   {baseElement, container, hydrate, queries, root, wrapper: WrapperComponent},
 ) {
-  act(() => {
-    if (hydrate) {
-      root.hydrate(
-        strictModeIfNeeded(wrapUiIfNeeded(ui, WrapperComponent)),
-        container,
-      )
-    } else {
-      root.render(
-        strictModeIfNeeded(wrapUiIfNeeded(ui, WrapperComponent)),
-        container,
-      )
-    }
-  })
-
   return {
     container,
     baseElement,
@@ -171,7 +107,7 @@ function renderRoot(
       })
     },
     rerender: rerenderUi => {
-      renderRoot(rerenderUi, {
+      createTestView(rerenderUi, {
         container,
         baseElement,
         root,
@@ -198,14 +134,7 @@ function renderRoot(
 
 function render(
   ui,
-  {
-    container,
-    baseElement = container,
-    legacyRoot = false,
-    queries,
-    hydrate = false,
-    wrapper,
-  } = {},
+  {container, baseElement = container, queries, hydrate = false, wrapper} = {},
 ) {
   if (!baseElement) {
     // default to document.body instead of documentElement to avoid output of potentially-large
@@ -219,8 +148,16 @@ function render(
   let root
   // eslint-disable-next-line no-negated-condition -- we want to map the evolution of this over time. The root is created first. Only later is it re-used so we don't want to read the case that happens later first.
   if (!mountedContainers.has(container)) {
-    const createRootImpl = legacyRoot ? createLegacyRoot : createConcurrentRoot
-    root = createRootImpl(container, {hydrate, ui, wrapper})
+    if (hydrate) {
+      act(() => {
+        root = ReactDOMClient.hydrateRoot(
+          container,
+          strictModeIfNeeded(wrapUiIfNeeded(ui, WrapperComponent)),
+        )
+      })
+    } else {
+      root = ReactDOMClient.createRoot(container)
+    }
 
     mountedRootEntries.push({container, root})
     // we'll add it to the mounted containers regardless of whether it's actually
@@ -238,7 +175,16 @@ function render(
     })
   }
 
-  return renderRoot(ui, {
+  if (!hydrate) {
+    act(() => {
+      root.render(
+        strictModeIfNeeded(wrapUiIfNeeded(ui, WrapperComponent)),
+        container,
+      )
+    })
+  }
+
+  return createTestView(ui, {
     container,
     baseElement,
     queries,

types/index.d.ts

@@ -67,17 +67,12 @@ export interface RenderOptions<
    */
   baseElement?: BaseElement
   /**
-   * If `hydrate` is set to `true`, then it will render with `ReactDOM.hydrate`. This may be useful if you are using server-side
-   *  rendering and use ReactDOM.hydrate to mount your components.
+   * If `hydrate` is set to `true`, then it will create a root with `ReactDOMClient.hydrateRoot`. This may be useful if you are using server-side
+   *  rendering and use ReactDOMClient.hydrateRoot to mount your components.
    *
    *  @see https://testing-library.com/docs/react-testing-library/api/#hydrate)
    */
   hydrate?: boolean
-  /**
-   * Set to `true` if you want to force synchronous `ReactDOM.render`.
-   * Otherwise `render` will default to concurrent React if available.
-   */
-  legacyRoot?: boolean
   /**
    * Queries to bind. Overrides the default set from DOM Testing Library unless merged.
    *