feat: make response encoder return an express middleware

Although it is not ideal, this at least matched the pattern that express
uses.

Author: bitgopatmcl

packages/express-wrapper/src/request.ts

@@ -45,7 +45,7 @@ export const decodeRequestAndEncodeResponse = (
 ): express.RequestHandler => {
   return createNamedFunction(
     'decodeRequestAndEncodeResponse' + httpRoute.method + apiName,
-    async (req, res) => {
+    async (req, res, next) => {
       const maybeRequest = httpRoute.request.decode(req);
       if (maybeRequest._tag === 'Left') {
         console.log('Request failed to decode');
@@ -63,10 +63,12 @@ export const decodeRequestAndEncodeResponse = (
       } catch (err) {
         console.warn('Error in route handler:', err);
         res.status(500).end();
+        next();
         return;
       }
 
-      responseEncoder(httpRoute, rawResponse, res);
+      const expressHandler = responseEncoder(httpRoute, rawResponse);
+      expressHandler(req, res, next);
     },
   );
 };

packages/express-wrapper/src/response.ts

@@ -22,28 +22,24 @@ export type NumericOrKeyedResponseType<R extends HttpRoute> =
 export type ResponseEncoder = (
   route: HttpRoute,
   serviceFnResponse: NumericOrKeyedResponseType<HttpRoute>,
-  expressRes: express.Response,
-) => void;
+) => express.RequestHandler;
 
-export const defaultResponseEncoder: ResponseEncoder = (
-  route,
-  serviceFnResponse,
-  expressRes,
-) => {
-  const { type, payload } = serviceFnResponse;
-  const status = typeof type === 'number' ? type : (KeyToHttpStatus as any)[type];
-  if (status === undefined) {
-    console.warn('Unknown status code returned');
-    expressRes.status(500).end();
-    return;
-  }
-  const responseCodec = route.response[status];
-  try {
-    expressRes.status(status).json(responseCodec!.encode(payload)).end();
-  } catch {
-    console.warn(
-      "Unable to encode route's return value, did you return the expected type?",
-    );
-    expressRes.status(500).end();
-  }
-};
+export const defaultResponseEncoder: ResponseEncoder =
+  (route, serviceFnResponse) => (_req, res) => {
+    const { type, payload } = serviceFnResponse;
+    const status = typeof type === 'number' ? type : (KeyToHttpStatus as any)[type];
+    if (status === undefined) {
+      console.warn('Unknown status code returned');
+      res.status(500).end();
+      return;
+    }
+    const responseCodec = route.response[status];
+    try {
+      res.status(status).json(responseCodec!.encode(payload)).end();
+    } catch {
+      console.warn(
+        "Unable to encode route's return value, did you return the expected type?",
+      );
+      res.status(500).end();
+    }
+  };