Support Promise<Target> in methods with static targets (#194)

source/sender.ts

@@ -14,7 +14,7 @@ import {
 } from "./types.js";
 import { isObject, MessengerError, __webextMessenger } from "./shared.js";
 import { log } from "./logging.js";
-import { type SetReturnType } from "type-fest";
+import { type Promisable, type SetReturnType } from "type-fest";
 import { handlers } from "./handlers.js";
 import { events } from "./events.js";
 
@@ -302,7 +302,7 @@ function getMethod<
   Type extends keyof MessengerMethods,
   Method extends MessengerMethods[Type],
   PublicMethodType extends PublicMethod<Method>
->(type: Type, target: Target | PageTarget): PublicMethodType;
+>(type: Type, target: Promisable<Target | PageTarget>): PublicMethodType;
 function getMethod<
   Type extends keyof MessengerMethods,
   Method extends MessengerMethods[Type],
@@ -315,21 +315,21 @@ function getMethod<
   PublicMethodWithDynamicTarget extends PublicMethodWithTarget<Method>
 >(
   type: Type,
-  target?: Target | PageTarget
+  target?: Promisable<Target | PageTarget>
 ): PublicMethodType | PublicMethodWithDynamicTarget {
-  if (arguments.length === 1) {
+  if (!target) {
     return messenger.bind(undefined, type, {}) as PublicMethodWithDynamicTarget;
   }
 
-  // @ts-expect-error `bind` types are junk
-  return messenger.bind(undefined, type, {}, target) as PublicMethodType;
+  return (async (...args: Parameters<Method>) =>
+    messenger(type, {}, await target, ...args)) as PublicMethodType;
 }
 
 function getNotifier<
   Type extends keyof MessengerMethods,
   Method extends MessengerMethods[Type],
   PublicMethodType extends SetReturnType<PublicMethod<Method>, void>
->(type: Type, target: Target | PageTarget): PublicMethodType;
+>(type: Type, target: Promisable<Target | PageTarget>): PublicMethodType;
 function getNotifier<
   Type extends keyof MessengerMethods,
   Method extends MessengerMethods[Type],
@@ -348,10 +348,10 @@ function getNotifier<
   >
 >(
   type: Type,
-  target?: Target | PageTarget
+  target?: Promisable<Target | PageTarget>
 ): PublicMethodType | PublicMethodWithDynamicTarget {
   const options = { isNotification: true };
-  if (arguments.length === 1) {
+  if (!target) {
     // @ts-expect-error `bind` types are junk
     return messenger.bind(
       undefined,
@@ -360,8 +360,10 @@ function getNotifier<
     ) as PublicMethodWithDynamicTarget;
   }
 
-  // @ts-expect-error `bind` types are junk
-  return messenger.bind(undefined, type, options, target) as PublicMethodType;
+  return ((...args: Parameters<Method>) => {
+    // Async wrapper needed to use `await` while preserving a non-Promise return type
+    (async () => messenger(type, options, await target, ...args))();
+  }) as PublicMethodType;
 }
 
 export { messenger, getMethod, getNotifier };

source/test/contentscript/api.test.ts

@@ -1,7 +1,11 @@
 import test from "tape";
 import { isBackground, isContentScript, isWebPage } from "webext-detect-page";
 import { type PageTarget, type Sender, type Target } from "../../index.js";
-import { errorTabDoesntExist, errorTargetClosedEarly } from "../../sender.js";
+import {
+  errorTabDoesntExist,
+  errorTargetClosedEarly,
+  getMethod,
+} from "../../sender.js";
 import {
   expectRejection,
   sleep,
@@ -393,6 +397,18 @@ function additionalTests() {
     getPageTitleNotification({ tabId });
     await closeTab(tabId);
   });
+
+  test("should support target promises in methods with static targets", async (t) => {
+    const tabIdPromise = openTab(
+      "https://fregante.github.io/pixiebrix-testing-ground/Will-receive-CS-calls/Promised-target"
+    );
+    const targetPromise = tabIdPromise.then((tabId) => ({ tabId }));
+
+    const request = getMethod("getPageTitle", targetPromise);
+    t.equal(await request(), "Promised target");
+
+    await closeTab(await tabIdPromise);
+  });
 }
 
 void testEveryTarget();