[v9] fix: primitive children mounting

packages/fiber/src/core/reconciler.tsx

@@ -104,7 +104,12 @@ export const extend = <T extends Catalogue | ConstructorRepresentation>(
  }
 }
 
-function createInstance(type: string, props: HostConfig['props'], root: RootStore): HostConfig['instance'] {
+function createInstance(
+ type: string,
+ props: HostConfig['props'],
+ root: RootStore,
+ flushPrimitive = true,
+): HostConfig['instance'] {
  // Get target from catalogue
  const name = `${type[0].toUpperCase()}${type.slice(1)}`
  const target = catalogue[name]
@@ -121,6 +126,9 @@ function createInstance(type: string, props: HostConfig['props'], root: RootStor
  // Throw if an object or literal was passed for args
  if (props.args !== undefined && !Array.isArray(props.args)) throw new Error('R3F: The args prop must be an array!')
 
+ // Regenerate the R3F instance for primitives to simulate a new object
+ if (flushPrimitive && type === 'primitive' && props.object?.__r3f) delete props.object.__r3f
+
  // Create instance
  const instance = prepare(props.object, root, type, props)
 
@@ -309,7 +317,12 @@ function switchInstance(
  if (oldInstance.isHidden) unhideInstance(oldInstance)
 
  // Create a new instance
- const newInstance = createInstance(type, props, oldInstance.root)
+ const newInstance = createInstance(type, props, oldInstance.root, false)
+
+ // Update attach props for primitives since we don't flush them
+ if (type === 'primitive') {
+ newInstance.props.attach = props.attach
+ }
 
  // Move children to new instance
  for (const child of oldInstance.children) {
@@ -377,7 +390,9 @@ export const reconciler = Reconciler<
  supportsMutation: true,
  supportsPersistence: false,
  supportsHydration: false,
- createInstance,
+ createInstance(type, props, root) {
+ return createInstance(type, props, root)
+ },
  removeChild,
  appendChild,
  appendInitialChild: appendChild,

packages/fiber/tests/renderer.test.tsx

@@ -85,6 +85,69 @@ describe('renderer', () => {
  expect(object.name).toBe('primitive')
  })
 
+ it('should remove children from primitive when unmounted', async () => {
+ const object = new THREE.Group()
+
+ function Parent({ children, show }: { children: React.ReactNode; show: boolean }) {
+ return show ? <primitive object={object}>{children}</primitive> : null
+ }
+
+ function Component({ show }: { show: boolean }) {
+ return (
+ <Parent show={show}>
+ <group name="A" />
+ <group name="B" />
+ </Parent>
+ )
+ }
+
+ const store = await act(async () => root.render(<Component show={true} />))
+ const { scene } = store.getState()
+
+ expect(scene.children.length).toBe(1)
+ expect(scene.children[0]).toBe(object)
+ expect(object.children.length).toBe(2)
+
+ await act(async () => root.render(<Component show={false} />))
+
+ expect(scene.children.length).toBe(0)
+ expect(object.children.length).toBe(0)
+ })
+
+ it('should remove then add children from primitive when key changes', async () => {
+ const object = new THREE.Group()
+
+ function Parent({ children, primitiveKey }: { children: React.ReactNode; primitiveKey: string }) {
+ return (
+ <primitive key={primitiveKey} object={object}>
+ {children}
+ </primitive>
+ )
+ }
+
+ function Component({ primitiveKey }: { primitiveKey: string }) {
+ return (
+ <Parent primitiveKey={primitiveKey}>
+ <group name="A" />
+ <group name="B" />
+ </Parent>
+ )
+ }
+
+ const store = await act(async () => root.render(<Component primitiveKey="A" />))
+ const { scene } = store.getState()
+
+ expect(scene.children.length).toBe(1)
+ expect(scene.children[0]).toBe(object)
+ expect(object.children.length).toBe(2)
+
+ await act(async () => root.render(<Component primitiveKey="B" />))
+
+ expect(scene.children.length).toBe(1)
+ expect(scene.children[0]).toBe(object)
+ expect(object.children.length).toBe(2)
+ })
+
  it('should go through lifecycle', async () => {
  const lifecycle: string[] = []
 
@@ -444,11 +507,9 @@ describe('renderer', () => {
  expect(scene.children.map((o) => o.name)).toStrictEqual(mixedArray.map((o) => o.name))
  })
 
- // TODO: fix this case, also see:
- // https://github.com/pmndrs/react-three-fiber/issues/1892
  // https://github.com/pmndrs/react-three-fiber/issues/3125
  // https://github.com/pmndrs/react-three-fiber/issues/3143
- it.skip('can swap 4 array primitives via attach', async () => {
+ it('can swap 4 array primitives via attach', async () => {
  const a = new THREE.Group()
  a.name = 'a'
  const b = new THREE.Group()