fix(bind): the default value can be undefined

packages/core/src/bind/connectFactoryObservable.test.tsx

@@ -522,6 +522,23 @@ describe("connectFactoryObservable", () => {
       subscription.unsubscribe()
     })
 
+    it("the defaultValue can be undefined", () => {
+      const number$ = new Subject<number>()
+      const [useNumber] = bind(() => number$, undefined)
+
+      const { result, unmount } = renderHook(() => useNumber())
+
+      expect(result.current).toBe(undefined)
+
+      actHook(() => {
+        number$.next(5)
+      })
+
+      expect(result.current).toBe(5)
+
+      unmount()
+    })
+
     it("if the observable hasn't emitted and a defaultValue is provided, it does not start suspense", () => {
       const number$ = new Subject<number>()
       const [useNumber] = bind(

packages/core/src/bind/connectFactoryObservable.ts

@@ -45,8 +45,8 @@ export default function connectFactoryObservable<A extends [], O>(
 
     const sharedObservable$ = shareLatest(
       getObservable(...input),
-      false,
       defaultValue,
+      false,
       () => {
         cache.delete(keys)
       },

packages/core/src/bind/connectObservable.test.tsx

@@ -650,6 +650,23 @@ describe("connectObservable", () => {
     expect(errorCallback).toHaveBeenCalled()
   })
 
+  it("the defaultValue can be undefined", () => {
+    const number$ = new Subject<number>()
+    const [useNumber] = bind(number$, undefined)
+
+    const { result, unmount } = renderHook(() => useNumber())
+
+    expect(result.current).toBe(undefined)
+
+    act(() => {
+      number$.next(5)
+    })
+
+    expect(result.current).toBe(5)
+
+    unmount()
+  })
+
   it("if the observable hasn't emitted and a defaultValue is provided, it does not start suspense", () => {
     const number$ = new Subject<number>()
     const [useNumber] = bind(number$, 0)

packages/core/src/bind/connectObservable.ts

@@ -21,7 +21,7 @@ export default function connectObservable<T>(
   observable: Observable<T>,
   defaultValue: T,
 ) {
-  const sharedObservable$ = shareLatest<T>(observable, false, defaultValue)
+  const sharedObservable$ = shareLatest<T>(observable, defaultValue, false)
   const useStaticObservable = () => useObservable(sharedObservable$)
   return [useStaticObservable, sharedObservable$] as const
 }

packages/core/src/bind/index.ts

@@ -46,8 +46,11 @@ export function bind<A extends unknown[], O>(
   defaultValue?: O,
 ): [(...args: A) => Exclude<O, typeof SUSPENSE>, (...args: A) => Observable<O>]
 
-export function bind(observable: any, defaultValue: any = EMPTY_VALUE) {
+export function bind(observable: any, defaultValue: any) {
   return (typeof observable === "function"
     ? (connectFactoryObservable as any)
-    : connectObservable)(observable, defaultValue)
+    : connectObservable)(
+    observable,
+    arguments.length > 1 ? defaultValue : EMPTY_VALUE,
+  )
 }

packages/core/src/internal/share-latest.ts

@@ -5,8 +5,8 @@ import { SUSPENSE } from "../SUSPENSE"
 
 const shareLatest = <T>(
   source$: Observable<T>,
+  defaultValue: T,
   shouldComplete = true,
-  defaultValue: T = EMPTY_VALUE,
   teardown = noop,
 ): BehaviorObservable<T> => {
   let subject: Subject<T> | null

packages/core/src/shareLatest.ts

@@ -1,5 +1,6 @@
 import { Observable, MonoTypeOperatorFunction } from "rxjs"
 import internalShareLatest from "./internal/share-latest"
+import { EMPTY_VALUE } from "./internal/empty-value"
 
 /**
  * A RxJS pipeable operator which shares and replays the latest emitted value.
@@ -17,4 +18,4 @@ import internalShareLatest from "./internal/share-latest"
  */
 export const shareLatest = <T>(): MonoTypeOperatorFunction<T> => (
   source$: Observable<T>,
-) => internalShareLatest(source$)
+) => internalShareLatest(source$, EMPTY_VALUE)