fix: preserve undefined in required inherited props

.changeset/clear-beds-refuse.md

@@ -0,0 +1,5 @@
+---
+"react-polymorphic": patch
+---
+
+Fix `Inherit` required-prop behavior to preserve inherited `undefined` unions when converting optional inherited props to required.

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "react-polymorphic",
-	"version": "1.0.1",
+	"version": "1.0.2",
 	"description": "Create polymorphic React 19+ components with strong TypeScript inference.",
 	"keywords": [
 		"react",

src/createPolymorph.ts

@@ -76,7 +76,7 @@ type RequiredKeys<T> = {
 /** Sets all keys in `K` of type `T` to required. */
 type Require<T, K extends PropertyKey> = Overwrite<
 	T,
-	Required<Pick<T, K extends keyof T ? K : never>>
+	{ [P in Extract<K, keyof T>]: T[P] }
 >;
 
 // Tag ------------------------------------------------------------------------

tests/integrations/createPolymorph/config.test.tsx

@@ -40,7 +40,7 @@ const ComponentE = createPolymorph<
 >(({ as: Tag = 'div', className, ...rest }) => {
 	return (
 		<Tag
-			className={typeof className === 'string' ? className : className()}
+			className={typeof className === 'function' ? className() : className}
 			{...rest}
 		/>
 	);

tests/types/createPolymorph/Inherit.test.tsx

@@ -36,5 +36,6 @@ type _ = [
 			true
 		>
 	>,
+	Assert<IsEqual<P['onClick'], ComponentProps<'button'>['onClick']>>,
 	Assert<IsEqual<IsOptionalKey<P, 'onClick'>, false>>
 ];