feat(types): allow Service<T> to handle non-WorkerEntrypoint default export (#4588)

* feat(types): allow Service<T> to handle non-WorkerEntrypoint default export

* restrict types accepted

* unwrap condition to avoid Fetcher<never>

Author: edmundhung

src/workerd/api/http.h

@@ -436,7 +436,16 @@ class Fetcher: public JsRpcClientProvider {
       });
     }
     JSG_TS_DEFINE(
-      type Service<T extends Rpc.WorkerEntrypointBranded | undefined = undefined> = Fetcher<T>;
+      type Service<
+        T extends
+          | (new (...args: any[]) => Rpc.WorkerEntrypointBranded)
+          | Rpc.WorkerEntrypointBranded
+          | ExportedHandler<any, any, any>
+          | undefined = undefined,
+      > = T extends new (...args: any[]) => Rpc.WorkerEntrypointBranded ? Fetcher<InstanceType<T>>
+        : T extends Rpc.WorkerEntrypointBranded ? Fetcher<T>
+        : T extends Exclude<Rpc.EntrypointBranded, Rpc.WorkerEntrypointBranded> ? never
+        : Fetcher<undefined>
     );
 
     if (!flags.getFetcherNoGetPutDelete()) {

types/generated-snapshot/experimental/index.d.ts

@@ -1760,8 +1760,19 @@ interface RequestInit<Cf = CfProperties> {
   signal?: AbortSignal | null;
   encodeResponseBody?: "automatic" | "manual";
 }
-type Service<T extends Rpc.WorkerEntrypointBranded | undefined = undefined> =
-  Fetcher<T>;
+type Service<
+  T extends
+    | (new (...args: any[]) => Rpc.WorkerEntrypointBranded)
+    | Rpc.WorkerEntrypointBranded
+    | ExportedHandler<any, any, any>
+    | undefined = undefined,
+> = T extends new (...args: any[]) => Rpc.WorkerEntrypointBranded
+  ? Fetcher<InstanceType<T>>
+  : T extends Rpc.WorkerEntrypointBranded
+    ? Fetcher<T>
+    : T extends Exclude<Rpc.EntrypointBranded, Rpc.WorkerEntrypointBranded>
+      ? never
+      : Fetcher<undefined>;
 type Fetcher<
   T extends Rpc.EntrypointBranded | undefined = undefined,
   Reserved extends string = never,

types/generated-snapshot/experimental/index.ts

@@ -1769,8 +1769,18 @@ export interface RequestInit<Cf = CfProperties> {
   encodeResponseBody?: "automatic" | "manual";
 }
 export type Service<
-  T extends Rpc.WorkerEntrypointBranded | undefined = undefined,
-> = Fetcher<T>;
+  T extends
+    | (new (...args: any[]) => Rpc.WorkerEntrypointBranded)
+    | Rpc.WorkerEntrypointBranded
+    | ExportedHandler<any, any, any>
+    | undefined = undefined,
+> = T extends new (...args: any[]) => Rpc.WorkerEntrypointBranded
+  ? Fetcher<InstanceType<T>>
+  : T extends Rpc.WorkerEntrypointBranded
+    ? Fetcher<T>
+    : T extends Exclude<Rpc.EntrypointBranded, Rpc.WorkerEntrypointBranded>
+      ? never
+      : Fetcher<undefined>;
 export type Fetcher<
   T extends Rpc.EntrypointBranded | undefined = undefined,
   Reserved extends string = never,

types/generated-snapshot/latest/index.d.ts

@@ -1727,8 +1727,19 @@ interface RequestInit<Cf = CfProperties> {
   signal?: AbortSignal | null;
   encodeResponseBody?: "automatic" | "manual";
 }
-type Service<T extends Rpc.WorkerEntrypointBranded | undefined = undefined> =
-  Fetcher<T>;
+type Service<
+  T extends
+    | (new (...args: any[]) => Rpc.WorkerEntrypointBranded)
+    | Rpc.WorkerEntrypointBranded
+    | ExportedHandler<any, any, any>
+    | undefined = undefined,
+> = T extends new (...args: any[]) => Rpc.WorkerEntrypointBranded
+  ? Fetcher<InstanceType<T>>
+  : T extends Rpc.WorkerEntrypointBranded
+    ? Fetcher<T>
+    : T extends Exclude<Rpc.EntrypointBranded, Rpc.WorkerEntrypointBranded>
+      ? never
+      : Fetcher<undefined>;
 type Fetcher<
   T extends Rpc.EntrypointBranded | undefined = undefined,
   Reserved extends string = never,

types/generated-snapshot/latest/index.ts

@@ -1736,8 +1736,18 @@ export interface RequestInit<Cf = CfProperties> {
   encodeResponseBody?: "automatic" | "manual";
 }
 export type Service<
-  T extends Rpc.WorkerEntrypointBranded | undefined = undefined,
-> = Fetcher<T>;
+  T extends
+    | (new (...args: any[]) => Rpc.WorkerEntrypointBranded)
+    | Rpc.WorkerEntrypointBranded
+    | ExportedHandler<any, any, any>
+    | undefined = undefined,
+> = T extends new (...args: any[]) => Rpc.WorkerEntrypointBranded
+  ? Fetcher<InstanceType<T>>
+  : T extends Rpc.WorkerEntrypointBranded
+    ? Fetcher<T>
+    : T extends Exclude<Rpc.EntrypointBranded, Rpc.WorkerEntrypointBranded>
+      ? never
+      : Fetcher<undefined>;
 export type Fetcher<
   T extends Rpc.EntrypointBranded | undefined = undefined,
   Reserved extends string = never,

types/test/types/rpc.ts

@@ -406,11 +406,10 @@ class TestNaughtyObject extends DurableObject {
 interface Env {
   REGULAR_SERVICE: Service;
   RPC_SERVICE: Service<TestEntrypoint>;
+  TYPEOF_RPC_SERVICE: Service<typeof TestEntrypoint>;
   NAUGHTY_SERVICE: Service<TestNaughtyEntrypoint>;
   // @ts-expect-error `BoringClass` isn't an RPC capable type
   __INVALID_RPC_SERVICE_1: Service<BoringClass>;
-  // @ts-expect-error `TestEntrypoint` is a `DurableObject`, not a `WorkerEntrypoint`
-  __INVALID_RPC_SERVICE_2: Service<TestObject>;
 
   REGULAR_OBJECT: DurableObjectNamespace;
   RPC_OBJECT: DurableObjectNamespace<TestObject>;