🔧 Fix 200 status code type inference in ~Routes

src/context.ts

@@ -18,6 +18,14 @@ import type {
 
 type InvertedStatusMapKey = keyof InvertedStatusMap
 
+type CheckExcessProps<T, U> = 0 extends 1 & T
+	? T // T is any
+	: U extends U
+		? Exclude<keyof T, keyof U> extends never
+			? T
+			: { [K in keyof U]: U[K] } & { [K in Exclude<keyof T, keyof U>]: never }
+		: never
+
 export type ErrorContext<
 	in out Route extends RouteSchema = {},
 	in out Singleton extends SingletonBase = {
@@ -81,9 +89,20 @@ export type ErrorContext<
 							: never
 				>(
 					code: Code,
-					response: T
+					response: CheckExcessProps<
+						T,
+						Code extends keyof Route['response']
+							? Route['response'][Code]
+							: Code extends keyof StatusMap
+								? // @ts-ignore StatusMap[Code] always valid because Code generic check
+									Route['response'][StatusMap[Code]]
+								: never
+					>
+				) => ElysiaCustomStatusResponse<
 					// @ts-ignore trust me bro
-				) => ElysiaCustomStatusResponse<Code, T>
+					Code,
+					T
+				>
 
 		/**
 		 * Path extracted from incoming URL

src/error.ts

@@ -39,20 +39,40 @@ const emptyHttpStatus = {
 	308: undefined
 } as const
 
+type CheckExcessProps<T, U> = 0 extends 1 & T
+	? T // T is any
+	: U extends U
+		? Exclude<keyof T, keyof U> extends never
+			? T
+			: { [K in keyof U]: U[K] } & { [K in Exclude<keyof T, keyof U>]: never }
+		: never
+
 export type SelectiveStatus<in out Res> = <
 	const Code extends
 		| keyof Res
-		| InvertedStatusMap[Extract<keyof InvertedStatusMap, keyof Res>]
->(
-	code: Code,
-	response: Code extends keyof Res
+		| InvertedStatusMap[Extract<keyof InvertedStatusMap, keyof Res>],
+	T extends Code extends keyof Res
 		? Res[Code]
 		: Code extends keyof StatusMap
 			? // @ts-ignore StatusMap[Code] always valid because Code generic check
 				Res[StatusMap[Code]]
 			: never
+>(
+	code: Code,
+	response: CheckExcessProps<
+		T,
+		Code extends keyof Res
+			? Res[Code]
+			: Code extends keyof StatusMap
+				? // @ts-ignore StatusMap[Code] always valid because Code generic check
+					Res[StatusMap[Code]]
+				: never
+	>
+) => ElysiaCustomStatusResponse<
 	// @ts-ignore trust me bro
-) => ElysiaCustomStatusResponse<Code, T>
+	Code,
+	T
+>
 
 export class ElysiaCustomStatusResponse<
 	const in out Code extends number | keyof StatusMap,

src/types.ts

@@ -452,7 +452,7 @@ interface OptionalField {
 export type UnwrapSchema<
 	Schema extends AnySchema | string | undefined,
 	Definitions extends DefinitionBase['typebox'] = {}
-> = undefined extends Schema
+> = Schema extends undefined
 	? unknown
 	: Schema extends TSchema
 		? Schema extends OptionalField

test/types/index.ts

@@ -1,15 +1,16 @@
 /* eslint-disable @typescript-eslint/no-unused-vars */
+
+import { expectTypeOf } from 'expect-type'
 import {
-	t,
+	type Cookie,
 	Elysia,
-	Cookie,
 	file,
-	sse,
+	form,
 	SSEPayload,
+	sse,
 	status,
-	form
+	t
 } from '../../src'
-import { expectTypeOf } from 'expect-type'
 
 const app = new Elysia()
 
@@ -2603,9 +2604,7 @@ type a = keyof {}
 		yield 'b'
 	}
 
-	const app = new Elysia().get('/', function () {
-		return sse(a())
-	})
+	const app = new Elysia().get('/', () => sse(a()))
 
 	expectTypeOf<
 		(typeof app)['~Routes']['get']['response'][200]
@@ -2630,9 +2629,7 @@ type a = keyof {}
 		yield 'b'
 	}
 
-	const app = new Elysia().get('/', function () {
-		return sse(a())
-	})
+	const app = new Elysia().get('/', () => sse(a()))
 
 	expectTypeOf<
 		(typeof app)['~Routes']['get']['response'][200]
@@ -2657,9 +2654,9 @@ type a = keyof {}
 		yield 'b'
 	}
 
-	const app = new Elysia().get('/', function () {
-		return sse(undefined as any as ReadableStream<'a'>)
-	})
+	const app = new Elysia().get('/', () =>
+		sse(undefined as any as ReadableStream<'a'>)
+	)
 
 	expectTypeOf<
 		(typeof app)['~Routes']['get']['response'][200]
@@ -2673,9 +2670,7 @@ type a = keyof {}
 // infer ReadableStream to Iterable
 {
 	const app = new Elysia()
-		.get('/', function () {
-			return undefined as any as ReadableStream<'a'>
-		})
+		.get('/', () => undefined as any as ReadableStream<'a'>)
 		.listen(3000)
 
 	expectTypeOf<
@@ -2846,7 +2841,7 @@ type a = keyof {}
 		'/mirror',
 		async ({ status, body }) => {
 			if (Math.random() > 0.5)
-				// @ts-ignore
+				// @ts-expect-error - should reject extra 'body' property
 				return status(201, { body, success: false })
 
 			// @ts-expect-error
@@ -2873,3 +2868,57 @@ type a = keyof {}
 		}
 	)
 }
+
+// Status code 200 type inference (issue #1584)
+{
+	const app = new Elysia().get(
+		'/',
+		() => ({ message: 'Hello Elysia' as const }),
+		{
+			response: {
+				200: t.Object({
+					message: t.Literal('Hello Elysia')
+				})
+			}
+		}
+	)
+
+	type AppResponse = (typeof app)['~Routes']['get']['response']
+
+	// Should properly infer the 200 response type, not [x: string]: any
+	const _typeTest: AppResponse extends {
+		200: { message: 'Hello Elysia' }
+	}
+		? true
+		: false = true
+
+	// Test with multiple status codes including 200
+	const app2 = new Elysia().post(
+		'/test',
+		({ status }) => {
+			if (Math.random() > 0.5) {
+				return status(200, { message: 'Hello Elysia' as const })
+			}
+			return status(422, { error: 'Validation error' })
+		},
+		{
+			response: {
+				200: t.Object({
+					message: t.Literal('Hello Elysia')
+				}),
+				422: t.Object({
+					error: t.String()
+				})
+			}
+		}
+	)
+
+	type App2Response = (typeof app2)['~Routes']['test']['post']['response']
+
+	const _typeTest2: App2Response extends {
+		200: { message: 'Hello Elysia' }
+		422: { error: string }
+	}
+		? true
+		: false = true
+}