refactor: Tweak asV2Middleware signatures

Author: rekmarks

packages/json-rpc-engine/src/README.md

@@ -65,13 +65,10 @@ const middleware2 = (req, res, next, end) => {
 const v2Engine2 = JsonRpcEngineV2.create({
   middleware: [asV2Middleware(middleware1, middleware2)],
 });
-
-// Or pass an array of legacy middlewares
-const v2Engine3 = JsonRpcEngineV2.create({
-  middleware: [asV2Middleware([middleware1, middleware2])],
-});
 ```
 
+#### Context propagation
+
 Non-JSON-RPC string properties on the request object will be copied over to the V2 engine's `context` object
 once the legacy engine is done with the request, _unless_ they already exist on the `context`, in which case
 they will be ignored.

packages/json-rpc-engine/src/asV2Middleware.test.ts

@@ -156,28 +156,6 @@ describe('asV2Middleware', () => {
       expect(middleware2).toHaveBeenCalledTimes(1);
     });
 
-    it('accepts an array of legacy middlewares', async () => {
-      const middleware1 = jest.fn((req, _res, next) => {
-        req.visited1 = true;
-        next();
-      });
-
-      const middleware2 = jest.fn((req, res, _next, end) => {
-        expect(req.visited1).toBe(true);
-        res.result = 'array-result';
-        end();
-      });
-
-      const v2Engine = JsonRpcEngineV2.create({
-        middleware: [asV2Middleware([middleware1, middleware2])],
-      });
-
-      const result = await v2Engine.handle(makeRequest());
-      expect(result).toBe('array-result');
-      expect(middleware1).toHaveBeenCalledTimes(1);
-      expect(middleware2).toHaveBeenCalledTimes(1);
-    });
-
     it('forwards errors from legacy middleware', async () => {
       const legacyMiddleware = jest.fn((_req, res, _next, end) => {
         res.error = rpcErrors.internal('legacy-error');

packages/json-rpc-engine/src/asV2Middleware.ts

@@ -10,11 +10,9 @@ import {
 import type {
   JsonRpcEngineEndCallback,
   JsonRpcEngineNextCallback,
-} from './JsonRpcEngine';
-import {
   JsonRpcEngine,
-  type JsonRpcMiddleware as LegacyMiddleware,
 } from './JsonRpcEngine';
+import { type JsonRpcMiddleware as LegacyMiddleware } from './JsonRpcEngine';
 import { mergeMiddleware } from './mergeMiddleware';
 import {
   deepClone,
@@ -32,57 +30,49 @@ import type {
 } from './v2/JsonRpcEngineV2';
 
 /**
- * Convert a legacy {@link JsonRpcEngine} or an array of legacy middlewares into a {@link JsonRpcEngineV2} middleware.
+ * Convert a legacy {@link JsonRpcEngine} into a {@link JsonRpcEngineV2} middleware.
  *
- * @param engineOrMiddlewares - The legacy engine or array of legacy middlewares to convert.
+ * @param engine - The legacy engine to convert.
  * @returns The {@link JsonRpcEngineV2} middleware.
  */
 export function asV2Middleware<
   Params extends JsonRpcParams,
   Request extends JsonRpcRequest<Params>,
->(
-  engineOrMiddlewares: JsonRpcEngine | LegacyMiddleware<JsonRpcParams, Json>[],
-): JsonRpcMiddleware<Request>;
+>(engine: JsonRpcEngine): JsonRpcMiddleware<Request>;
 
 /**
- * Convert one or more legacy middlewares into a {@link JsonRpcEngineV2} middleware.
+ * Convert one or more legacy middleware into a {@link JsonRpcEngineV2} middleware.
  *
- * @param middlewares - The legacy middleware(s) to convert.
+ * @param middleware - The legacy middleware(s) to convert.
  * @returns The {@link JsonRpcEngineV2} middleware.
  */
 export function asV2Middleware<
   Params extends JsonRpcParams,
   Request extends JsonRpcRequest<Params>,
 >(
-  ...middlewares: LegacyMiddleware<JsonRpcParams, Json>[]
+  ...middleware: LegacyMiddleware<JsonRpcParams, Json>[]
 ): JsonRpcMiddleware<Request>;
 
 /**
  * Implementation of asV2Middleware that handles all input types.
  *
- * @param engineOrMiddleware - A legacy engine, a single legacy middleware, or an array of legacy middlewares.
- * @param rest - Additional legacy middlewares when the first argument is a single middleware.
+ * @param engineOrMiddleware - A legacy engine, a single legacy middleware, or an array of legacy middleware.
+ * @param rest - Additional legacy middleware when the first argument is a single middleware.
  * @returns The {@link JsonRpcEngineV2} middleware.
  */
 export function asV2Middleware<
   Params extends JsonRpcParams,
   Request extends JsonRpcRequest<Params>,
 >(
-  engineOrMiddleware:
-    | JsonRpcEngine
-    | LegacyMiddleware<JsonRpcParams, Json>
-    | LegacyMiddleware<JsonRpcParams, Json>[],
+  engineOrMiddleware: JsonRpcEngine | LegacyMiddleware<JsonRpcParams, Json>,
   ...rest: LegacyMiddleware<JsonRpcParams, Json>[]
 ): JsonRpcMiddleware<Request> {
   // Determine the legacy middleware function from input(s)
   const middleware =
-    engineOrMiddleware instanceof JsonRpcEngine
-      ? engineOrMiddleware.asMiddleware()
-      : mergeMiddleware(
-          Array.isArray(engineOrMiddleware)
-            ? engineOrMiddleware
-            : [engineOrMiddleware, ...rest],
-        );
+    typeof engineOrMiddleware === 'function'
+      ? mergeMiddleware([engineOrMiddleware, ...rest])
+      : engineOrMiddleware.asMiddleware();
+
   return async ({ request, context, next }) => {
     const req = deepClone(request) as JsonRpcRequest<Params>;
     propagateToRequest(req, context);