Relax fallback prop to support broader ReactNode type

Author: bvaughn

src/ErrorBoundary.test.tsx

@@ -56,7 +56,7 @@ describe("ErrorBoundary", () => {
     expect(container.textContent).toBe("Content");
   });
 
-  describe("callback props", () => {
+  describe("fallback props", () => {
     let errorBoundaryRef: RefObject<ErrorBoundary>;
 
     beforeEach(() => {
@@ -66,11 +66,7 @@ describe("ErrorBoundary", () => {
     function render(props: Omit<ErrorBoundaryPropsWithFallback, "fallback">) {
       act(() => {
         root.render(
-          <ErrorBoundary
-            {...props}
-            fallback={<div>Error</div>}
-            ref={errorBoundaryRef}
-          >
+          <ErrorBoundary {...props} fallback="Error" ref={errorBoundaryRef}>
             <MaybeThrows>Content</MaybeThrows>
           </ErrorBoundary>
         );

src/ErrorBoundary.ts

@@ -1,5 +1,5 @@
 import { isDevelopment } from "#is-development";
-import { Component, createElement, ErrorInfo, isValidElement } from "react";
+import { Component, createElement, ErrorInfo } from "react";
 import { ErrorBoundaryContext } from "./ErrorBoundaryContext";
 import { ErrorBoundaryProps, FallbackProps } from "./types";
 
@@ -94,7 +94,7 @@ export class ErrorBoundary extends Component<
         childToRender = fallbackRender(props);
       } else if (FallbackComponent) {
         childToRender = createElement(FallbackComponent, props);
-      } else if (fallback === null || isValidElement(fallback)) {
+      } else if (fallback !== undefined) {
         childToRender = fallback;
       } else {
         if (isDevelopment) {

src/types.ts

@@ -38,10 +38,7 @@ export type ErrorBoundaryPropsWithRender = ErrorBoundarySharedProps & {
 };
 
 export type ErrorBoundaryPropsWithFallback = ErrorBoundarySharedProps & {
-  fallback: ReactElement<
-    unknown,
-    string | FunctionComponent | typeof Component
-  > | null;
+  fallback: ReactNode;
   FallbackComponent?: never;
   fallbackRender?: never;
 };