🔧 fix: #1410 handle union derive/resolve property

Author: SaltyAom

CHANGELOG.md

@@ -1,7 +1,11 @@
 # 1.4.6 - 15 Sep 2025
 Improvement:
-- strictly check for 200 inline status code
+- [#1406](https://github.com/elysiajs/elysia/issues/1406) strictly check for 200 inline status code
 - coerce union status value and return type
+- add `BunHTMLBundleLike` to Elysia inline handler
+
+Bug fix:
+- [#1410](https://github.com/elysiajs/elysia/issues/1410) handle union derive/resolve
 
 # 1.4.5 - 15 Sep 2025
 Improvement:

example/a.ts

@@ -1,27 +1,19 @@
-import { Prettify } from 'elysia/types'
-import { Elysia, ElysiaCustomStatusResponse, t } from '../src'
-import { req } from '../test/utils'
-import { Tuple } from '../src/types'
+import { Elysia } from '../src'
 
-type PickOne<T> = T extends any ? T : never
+export interface AuthData {
+	id: number
+}
 
-new Elysia().get(
-	'/test',
-	({ status }) => {
-		return status(200, { key2: 's', id: 2 })
-	},
-	{
-		response: {
-			200: t.Union([
-				t.Object({
-					key2: t.String(),
-					id: t.Literal(2)
-				}),
-				t.Object({
-					key: t.Number(),
-					id: t.Literal(1)
-				})
-			])
-		}
-	}
-)
+const app = new Elysia()
+	.derive(({ request }) => {
+		const apiKey = request.headers.get('x-api-key')
+		if (!apiKey) return { auth: null }
+
+		return { auth: { id: 1 } satisfies AuthData }
+	})
+	.onBeforeHandle(({ auth, set }) => {
+		console.log(auth?.id)
+		console.log(set.status)
+	})
+
+app['~Volatile']

src/types.ts

@@ -1148,21 +1148,22 @@ type InlineResponse =
 	| BunHTMLBundlelike
 
 type LastOf<T> =
-    UnionToIntersect<T extends any ? () => T : never> extends () => infer R
-        ? R
-        : never;
+	UnionToIntersect<T extends any ? () => T : never> extends () => infer R
+		? R
+		: never
 
-type Push<T extends any[], V> = [...T, V];
+type Push<T extends any[], V> = [...T, V]
 
-type TuplifyUnion<T, L = LastOf<T>, N = [T] extends [never] ? true : false> =
-    true extends N
-        ? []
-        : Push<TuplifyUnion<Exclude<T, L>>, L>;
+type TuplifyUnion<
+	T,
+	L = LastOf<T>,
+	N = [T] extends [never] ? true : false
+> = true extends N ? [] : Push<TuplifyUnion<Exclude<T, L>>, L>
 
-export type Tuple<T, A extends T[] = []> =
-    TuplifyUnion<T>['length'] extends A['length']
-        ? [...A]
-        : Tuple<T, [T, ...A]>;
+export type Tuple<
+	T,
+	A extends T[] = []
+> = TuplifyUnion<T>['length'] extends A['length'] ? [...A] : Tuple<T, [T, ...A]>
 
 export type InlineHandler<
 	Route extends RouteSchema = {},
@@ -2216,10 +2217,10 @@ type PartialIf<T, Condition extends boolean> = Condition extends true
 // Exclude return error()
 export type ExcludeElysiaResponse<T> = PartialIf<
 	Exclude<Awaited<T>, AnyElysiaCustomStatusResponse> extends infer A
-		? IsNever<A> extends true
+		? IsNever<A & {}> extends true
 			? {}
 			: // Intersect all union and fallback never to {}
-				UnionToIntersect<A & {}>
+				A & {}
 		: {},
 	undefined extends Awaited<T> ? true : false
 >

test/types/index.ts

@@ -2687,3 +2687,39 @@ type a = keyof {}
 {
 	new Elysia().get('/file', file('public/takodachi.png'))
 }
+
+// derive should add property union correctly
+{
+	const app = new Elysia()
+		.derive(({ request, status }) => {
+			const apiKey = request.headers.get('x-api-key')
+			if (!apiKey) return { auth: null }
+
+			if (Math.random() > 0.5) return status(401)
+
+			return { auth: { id: 1 } }
+		})
+		.onBeforeHandle(({ auth }) => {
+			expectTypeOf<typeof auth>().toEqualTypeOf<{
+				readonly id: 1
+			} | null>()
+		})
+}
+
+// resolve should add property union correctly
+{
+	const app = new Elysia()
+		.resolve(({ request, status }) => {
+			const apiKey = request.headers.get('x-api-key')
+			if (!apiKey) return { auth: null }
+
+			if (Math.random() > 0.5) return status(401)
+
+			return { auth: { id: 1 } }
+		})
+		.onBeforeHandle(({ auth }) => {
+			expectTypeOf<typeof auth>().toEqualTypeOf<{
+				readonly id: 1
+			} | null>()
+		})
+}