feat(react-components): add react 18 support #34456

dmytrokirpa · 2025-05-15T13:35:40Z

Summary

This PR addresses type incompatibilities introduced by React 18 that break our Slots API. Specifically, it fixes issues with ReactNode, RefAttributes, and several slot-related utility types. It also adjusts internal type declarations to better align with actual usage and React’s updated typings.

Previous Behavior

1. `ReactNode` Breaking Change

React 18 introduced stricter definitions for ReactNode, removing the {} catch-all in ReactFragment. This change breaks our slot typings, which previously relied on the broader compatibility of React 17:

React 17:

type ReactFragment = {} | ReactNodeArray;
type ReactNode = ReactChild | ReactFragment | ReactPortal | boolean | null | undefined;

React 18:

type ReactNode =
  | ReactElement
  | string
  | number
  | Iterable<ReactNode>
  | ReactPortal
  | boolean
  | null
  | undefined
  | ExperimentalReactNodes[keyof ExperimentalReactNodes];

🔗 Playground showing the issue

2. `RefAttributes` Change

In React 18, RefAttributes now uses LegacyRef<T> which includes support for string refs — something we don't support in our API.

React 17:

interface RefAttributes<T> {
  ref?: Ref<T>
}

React 18:

interface RefAttributes<T> {
  ref?: LegacyRef<T>
}

3. `FC` doesn't provides type for `children` prop, it should be explicitly defined

React 17:

const Component: React.FC = ({ children }) => <>{children}</>

React 18:

// `children` is not defined in React.FC
const Component: React.FC = ({ children }) => <>{children}</>

const Component: React.FC<{ children?: React.ReactNode }> = ({ children }) => <>{children}</>

New Behavior

Loosened type constraints in UnknownSlotProps
Previously, the children prop has type ReactNode | undefined, but this doesn’t work with the SlotRenderFunction and React 18. This change removes that restriction and to enable usage with React 18.
Updated SlotShorthandValue to accept Iterable<ReactNode>
React 18 expands ReactNode to include Iterable<ReactNode>, so this change ensures our shorthand slot values also support this structure. This enables support for JSX fragments and iterable rendering.
WithSlotRenderFunction adjusted for manual type assertions in React 18
In React 18, implicit inference of slot render functions may not work correctly due to stricter type definitions. Consumers must now use as or satisfies type assertions when passing a function to slot props.
Removed deprecated VoidFunctionComponent
VoidFunctionComponent is deprecated and unnecessary since ComponentType handles the same use cases. Removing it simplifies our generic types and avoids confusion.
cloneTriggerTree updated for broader children support
This utility function now assumes children can be more than just ReactNode. It aligns with the loosened constraints and supports broader use cases, including render functions or iterables.
Removed usage of React.RefAttributes in several utilities
With React 18, RefAttributes includes LegacyRef, which supports string refs — something we don’t allow. We’ve replaced it with more precise types to enforce our internal API constraints.
Added { children?: React.ReactNode } to fix story/test compatibility
Some stories and test utilities failed under React 18 due to missing children prop typing. So the fix is too use the React.PropsWithChildren<Props> or explicitly declare the children prop type.

React 18 type changes:

Slot render functions must now be manually typed in React 18:

// React 17 – works
<Button icon={{ children: () => 'Icon' }}>Label</Button>

// React 18 – breaks, Parameter 'children' implicitly has an 'any' type.
<Button icon={{ children: () => 'Icon' }}>Label</Button>

// React 18 – fixed by manual type assertion
<Button icon={{ children: (() => 'Icon') satisfies SlotRenderFunction<IconProps> }}>
  Label
</Button>

Future Plans

Migrate slot render function away from children to a dedicated prop to improve type inference.

Related Issues

github-actions · 2025-05-15T13:41:54Z

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
`react-accordion` Accordion (including children components)	`108.02 kB` `33.15 kB`	`108.066 kB` `33.169 kB`	`46 B` `19 B`
`react-avatar` Avatar	`49.376 kB` `15.835 kB`	`49.424 kB` `15.845 kB`	`48 B` `10 B`
`react-avatar` AvatarGroup	`20.177 kB` `7.974 kB`	`20.224 kB` `7.99 kB`	`47 B` `16 B`
`react-avatar` AvatarGroupItem	`63.52 kB` `20.047 kB`	`63.568 kB` `20.059 kB`	`48 B` `12 B`
`react-badge` Badge	`26.002 kB` `8.603 kB`	`26.049 kB` `8.623 kB`	`47 B` `20 B`
`react-badge` CounterBadge	`26.781 kB` `8.882 kB`	`26.829 kB` `8.899 kB`	`48 B` `17 B`
`react-badge` PresenceBadge	`25.789 kB` `9.472 kB`	`25.835 kB` `9.488 kB`	`46 B` `16 B`
`react-breadcrumb` @fluentui/react-breadcrumb - package	`115.069 kB` `31.86 kB`	`115.118 kB` `31.877 kB`	`49 B` `17 B`
`react-button` Button	`37.648 kB` `10.867 kB`	`37.694 kB` `10.883 kB`	`46 B` `16 B`
`react-button` CompoundButton	`44.059 kB` `12.168 kB`	`44.106 kB` `12.184 kB`	`47 B` `16 B`
`react-button` MenuButton	`42.457 kB` `12.216 kB`	`42.506 kB` `12.233 kB`	`49 B` `17 B`
`react-button` SplitButton	`50.527 kB` `13.782 kB`	`50.573 kB` `13.801 kB`	`46 B` `19 B`
`react-button` ToggleButton	`53.578 kB` `12.642 kB`	`53.625 kB` `12.655 kB`	`47 B` `13 B`
`react-card` Card - All	`102.52 kB` `28.908 kB`	`102.566 kB` `28.937 kB`	`46 B` `29 B`
`react-card` Card	`95.162 kB` `27.094 kB`	`95.212 kB` `27.103 kB`	`50 B` `9 B`
`react-card` CardFooter	`14.605 kB` `5.885 kB`	`14.651 kB` `5.9 kB`	`46 B` `15 B`
`react-card` CardHeader	`17.138 kB` `6.751 kB`	`17.184 kB` `6.764 kB`	`46 B` `13 B`
`react-card` CardPreview	`14.671 kB` `6.009 kB`	`14.718 kB` `6.026 kB`	`47 B` `17 B`
`react-checkbox` Checkbox	`35.189 kB` `12.093 kB`	`35.241 kB` `12.109 kB`	`52 B` `16 B`
`react-color-picker` ColorArea	`50.26 kB` `17.664 kB`	`50.309 kB` `17.678 kB`	`49 B` `14 B`
`react-color-picker` ColorPicker	`18.893 kB` `7.495 kB`	`18.939 kB` `7.509 kB`	`46 B` `14 B`
`react-color-picker` ColorSlider	`42.436 kB` `15.715 kB`	`42.482 kB` `15.728 kB`	`46 B` `13 B`
`react-combobox` Combobox (including child components)	`107.617 kB` `35.006 kB`	`107.663 kB` `35.031 kB`	`46 B` `25 B`
`react-combobox` Dropdown (including child components)	`108.241 kB` `34.952 kB`	`108.293 kB` `34.976 kB`	`52 B` `24 B`
`react-components` react-components: Button, FluentProvider & webLightTheme	`69.732 kB` `20.259 kB`	`69.779 kB` `20.273 kB`	`47 B` `14 B`
`react-components` react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	`227.58 kB` `65.885 kB`	`227.642 kB` `65.911 kB`	`62 B` `26 B`
`react-components` react-components: FluentProvider & webLightTheme	`44.567 kB` `14.62 kB`	`44.613 kB` `14.641 kB`	`46 B` `21 B`
`react-components` react-components: entire library	`1.231 MB` `310.272 kB`	`1.231 MB` `310.283 kB`	`87 B` `11 B`
`react-datepicker-compat` DatePicker Compat	`227.319 kB` `64.364 kB`	`227.365 kB` `64.386 kB`	`46 B` `22 B`
`react-dialog` Dialog (including children components)	`102.547 kB` `30.738 kB`	`102.593 kB` `30.76 kB`	`46 B` `22 B`
`react-divider` Divider	`21.399 kB` `7.964 kB`	`21.445 kB` `7.981 kB`	`46 B` `17 B`
`react-field` Field	`23.515 kB` `8.917 kB`	`23.561 kB` `8.937 kB`	`46 B` `20 B`
`react-image` Image	`15.432 kB` `6.251 kB`	`15.478 kB` `6.266 kB`	`46 B` `15 B`
`react-input` Input	`28.085 kB` `9.456 kB`	`28.137 kB` `9.476 kB`	`52 B` `20 B`
`react-label` Label	`14.742 kB` `6.007 kB`	`14.788 kB` `6.023 kB`	`46 B` `16 B`
`react-link` Link	`17.671 kB` `7.155 kB`	`17.717 kB` `7.167 kB`	`46 B` `12 B`
`react-list` List	`89.684 kB` `26.704 kB`	`89.731 kB` `26.718 kB`	`47 B` `14 B`
`react-list` ListItem	`113.027 kB` `33.481 kB`	`113.073 kB` `33.501 kB`	`46 B` `20 B`
`react-menu` Menu (including children components)	`157.228 kB` `47.266 kB`	`157.289 kB` `47.31 kB`	`61 B` `44 B`
`react-menu` Menu (including selectable components)	`160.21 kB` `47.87 kB`	`160.271 kB` `47.909 kB`	`61 B` `39 B`
`react-message-bar` MessageBar (all components)	`24.948 kB` `9.289 kB`	`24.994 kB` `9.303 kB`	`46 B` `14 B`
`react-persona` Persona	`56.267 kB` `17.712 kB`	`56.315 kB` `17.724 kB`	`48 B` `12 B`
`react-popover` Popover	`132.988 kB` `41.417 kB`	`133.031 kB` `41.442 kB`	`43 B` `25 B`
`react-progress` ProgressBar	`17.156 kB` `6.9 kB`	`17.202 kB` `6.919 kB`	`46 B` `19 B`
`react-provider` FluentProvider	`24.743 kB` `8.92 kB`	`24.789 kB` `8.94 kB`	`46 B` `20 B`
`react-radio` Radio	`32.743 kB` `10.357 kB`	`32.789 kB` `10.375 kB`	`46 B` `18 B`
`react-radio` RadioGroup	`15.831 kB` `6.446 kB`	`15.878 kB` `6.462 kB`	`47 B` `16 B`
`react-select` Select	`27.804 kB` `10.14 kB`	`27.856 kB` `10.16 kB`	`52 B` `20 B`
`react-slider` Slider	`38.129 kB` `12.803 kB`	`38.175 kB` `12.82 kB`	`46 B` `17 B`
`react-spinbutton` SpinButton	`35.284 kB` `11.765 kB`	`35.337 kB` `11.785 kB`	`53 B` `20 B`
`react-spinner` Spinner	`25.317 kB` `8.553 kB`	`25.363 kB` `8.57 kB`	`46 B` `17 B`
`react-swatch-picker` @fluentui/react-swatch-picker - package	`106.899 kB` `30.866 kB`	`106.945 kB` `30.882 kB`	`46 B` `16 B`
`react-switch` Switch	`35.371 kB` `11.336 kB`	`35.418 kB` `11.352 kB`	`47 B` `16 B`
`react-table` DataGrid	`162.071 kB` `45.872 kB`	`162.123 kB` `45.891 kB`	`52 B` `19 B`
`react-table` Table (Primitives only)	`42.825 kB` `13.882 kB`	`42.884 kB` `13.906 kB`	`59 B` `24 B`
`react-table` Table as DataGrid	`132.323 kB` `36.672 kB`	`132.381 kB` `36.697 kB`	`58 B` `25 B`
`react-table` Table (Selection only)	`70.693 kB` `20.017 kB`	`70.752 kB` `20.038 kB`	`59 B` `21 B`
`react-table` Table (Sort only)	`69.336 kB` `19.63 kB`	`69.395 kB` `19.651 kB`	`59 B` `21 B`
`react-tag-picker` @fluentui/react-tag-picker - package	`188.73 kB` `56.597 kB`	`188.782 kB` `56.623 kB`	`52 B` `26 B`
`react-tags` InteractionTag	`15.506 kB` `6.232 kB`	`15.552 kB` `6.249 kB`	`46 B` `17 B`
`react-tags` Tag	`30.306 kB` `9.905 kB`	`30.353 kB` `9.925 kB`	`47 B` `20 B`
`react-tags` TagGroup	`84.031 kB` `24.92 kB`	`84.078 kB` `24.939 kB`	`47 B` `19 B`
`react-text` Text - Default	`17.133 kB` `6.737 kB`	`17.179 kB` `6.753 kB`	`46 B` `16 B`
`react-text` Text - Wrappers	`20.293 kB` `7.063 kB`	`20.339 kB` `7.078 kB`	`46 B` `15 B`
`react-textarea` Textarea	`26.652 kB` `9.764 kB`	`26.704 kB` `9.784 kB`	`52 B` `20 B`
`react-timepicker-compat` TimePicker	`110.6 kB` `36.56 kB`	`110.646 kB` `36.578 kB`	`46 B` `18 B`
`react-toast` Toast (including Toaster)	`103.062 kB` `30.965 kB`	`103.119 kB` `30.976 kB`	`57 B` `11 B`
`react-tooltip` Tooltip	`58.64 kB` `20.312 kB`	`58.686 kB` `20.336 kB`	`46 B` `24 B`
`react-tree` FlatTree	`148.801 kB` `42.694 kB`	`148.849 kB` `42.711 kB`	`48 B` `17 B`
`react-tree` PersonaFlatTree	`149.559 kB` `42.802 kB`	`149.607 kB` `42.818 kB`	`48 B` `16 B`
`react-tree` PersonaTree	`145.818 kB` `41.691 kB`	`145.865 kB` `41.699 kB`	`47 B` `8 B`
`react-tree` Tree	`145.066 kB` `41.565 kB`	`145.113 kB` `41.575 kB`	`47 B` `10 B`

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
`global-context` createContext	`510 B` `328 B`
`global-context` createContextSelector	`537 B` `339 B`
`react-aria` ARIA - Default	`237 B` `181 B`
`react-calendar-compat` Calendar Compat	`149.672 kB` `39.914 kB`
`react-jsx-runtime` Classic Pragma	`1.101 kB` `550 B`
`react-jsx-runtime` JSX Dev Runtime	`3.815 kB` `1.659 kB`
`react-jsx-runtime` JSX Runtime	`4.411 kB` `1.901 kB`
`react-motion` @fluentui/react-motion - createMotionComponent()	`3.995 kB` `1.755 kB`
`react-motion` @fluentui/react-motion - createPresenceComponent()	`4.858 kB` `2.128 kB`
`react-motion` @fluentui/react-motion - PresenceGroup	`1.727 kB` `823 B`
`react-overflow` hooks only	`12.832 kB` `4.828 kB`
`react-portal` Portal	`15.259 kB` `5.319 kB`
`react-portal-compat` PortalCompatProvider	`8.386 kB` `2.624 kB`
`react-positioning` usePositioning	`28.865 kB` `10.146 kB`
`react-teaching-popover` TeachingPopover	`102.747 kB` `30.737 kB`
`react-utilities` SSRProvider	`180 B` `160 B`

_{🤖 This report was generated against 43876a550a6da7f1712f1456a4d88acc373a1dd4}

github-actions · 2025-05-15T13:42:07Z

Pull request demo site: URL

apps/react-18-tests-v9/tsconfig.react-18.json

apps/react-18-tests-v9/src/issues.tsx

change/@fluentui-react-accordion-70e37d4f-804b-494a-9d94-31840668c018.json

...s/react-drawer/library/src/components/DrawerHeaderTitle/useDrawerHeaderTitleStyles.styles.ts

packages/react-components/react-menu/library/src/components/MenuItem/useMenuItem.tsx

...ages/react-components/react-portal/library/src/components/Portal/usePortalMountNode.test.tsx

...ct-components/react-tag-picker/library/src/components/TagPickerButton/useTagPickerButton.tsx

packages/react-components/react-utilities/src/compose/deprecated/getSlots.ts

packages/react-components/react-utilities/src/utils/types.ts

packages/react-components/react-utilities/src/index.ts

packages/react-components/react-utilities/src/compose/types.ts

packages/react-components/react-breadcrumb/stories/src/Breadcrumb/index.stories.tsx

alexgorbatchev · 2025-05-29T16:33:21Z

Lets go! Woohoo!! 🥳

dmytrokirpa · 2025-06-03T16:53:52Z

apps/react-18-tests-v9/src/issues.tsx

@@ -72,6 +72,7 @@ import type {
    ...defaultMenuProps,
  };

+  // @ts-expect-error - Slot type mismatch


TODO: add proper explanation

dmytrokirpa · 2025-06-03T16:58:04Z

packages/react-components/react-table/library/src/components/DataGridBody/DataGridBody.tsx

@@ -10,14 +10,16 @@ import { useCustomStyleHook_unstable } from '@fluentui/react-shared-contexts';
 * DataGridBody component
 */
 export const DataGridBody: ForwardRefComponent<DataGridBodyProps> &


Not sure if we need the type declaration part since we already do type-casting.

dmytrokirpa · 2025-06-04T09:43:32Z

.github/workflows/bundle-size.yml

@@ -45,7 +45,9 @@ jobs:
        run: yarn nx affected -t bundle-size --nxBail

      - name: Compare bundle size with base
-        run: npx monosize compare-reports --branch=${{ github.event.pull_request.base.ref }} --output=markdown --quiet > ./monosize-report.md
+        # FIXME: undo this before PR to master
+        run: npx monosize compare-reports --branch=master --output=markdown --quiet > ./monosize-report.md


TODO: revert before merge

dmytrokirpa · 2025-06-04T09:43:59Z

apps/react-17-tests-v9/src/issues.tsx

@@ -74,6 +74,7 @@ import type {

  slot.always(props.menuButton, {
    defaultProps: menuButtonDefaultProps,
+    // @ts-expect-error - Slot type mismatch


TODO: add a proper explanation

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dmytrokirpa changed the title ~~React components/react 18~~ chore: slot api support for react 17/18 May 26, 2025

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dmytrokirpa changed the title ~~chore: slot api support for react 17/18~~ feat: add support for react 18 May 26, 2025

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dmytrokirpa marked this pull request as ready for review May 28, 2025 16:09

dmytrokirpa requested review from a team, sopranopillow, mltejera, ValentinaKozlova, marcosmoura and Mitch-At-Work as code owners May 28, 2025 16:09

Hotell changed the title ~~feat: add support for react 18~~ feat(react-components): add react 18 support May 28, 2025

Hotell force-pushed the react-components/react-18 branch from 80ea1e6 to 0fb509e Compare June 3, 2025 15:50

dmytrokirpa force-pushed the react-components/react-18 branch from 0fb509e to bc4bf6d Compare June 3, 2025 16:25

dmytrokirpa force-pushed the react-components/react-18 branch from bc4bf6d to 2af8cd2 Compare June 3, 2025 16:52

dmytrokirpa requested a review from GeoffCoxMSFT as a code owner June 3, 2025 16:52

dmytrokirpa marked this pull request as draft June 3, 2025 16:52

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dmytrokirpa added 3 commits June 3, 2025 20:59

feat(react-utilitles): add react 18 support for slots

68bd02b

change

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update api snapshot

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dmytrokirpa force-pushed the react-components/react-18 branch from 2af8cd2 to 98cb88c Compare June 3, 2025 18:59

dmytrokirpa added 2 commits June 3, 2025 23:22

dismiss ts error

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change file

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fix(react-components): use custom RefAttributes instead of React.RefAttributes #34590

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use our own RefAttributes type for getIntrinsicElementProps

2074317

dmytrokirpa force-pushed the react-components/react-18 branch from 7099472 to 2074317 Compare June 4, 2025 14:00

Merge branch 'master' into react-components/react-18

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This was referenced Jun 4, 2025

chore(react-tests-v9): mute invalid patterns and provide correct examples #34591

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feat(public-docsite-v9): add official platform support docs including React Versions #34599

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Summary

Previous Behavior

1. ReactNode Breaking Change

2. RefAttributes Change

3. FC doesn't provides type for children prop, it should be explicitly defined

New Behavior

React 18 type changes:

Future Plans

Related Issues

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📊 Bundle size report

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dmytrokirpa commented May 15, 2025 •

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1. `ReactNode` Breaking Change

2. `RefAttributes` Change

3. `FC` doesn't provides type for `children` prop, it should be explicitly defined

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