chore: improve Sentry express error handling

apps/backend/src/auth/request.ts

@@ -10,7 +10,7 @@ export class AuthError extends Error {}
 const getTokenFromAuthHeader = (authHeader: string) => {
   const auth = authorization.parse(authHeader);
   if (auth.scheme !== "Bearer") {
-    throw new AuthError("Invalid auth scheme");
+    throw new AuthError(`Invalid auth scheme: ${auth.scheme || "no scheme"}`);
   }
   if (typeof auth.token !== "string" || !auth.token) {
     throw new AuthError("Invalid auth token");

apps/backend/src/web/api/index.ts

@@ -1,7 +1,5 @@
-import * as Sentry from "@sentry/node";
 import { Application, Router } from "express";
 
-import { errorHandler } from "../middlewares/errorHandler.js";
 import { apiMiddleware as githubApiMiddleware } from "../middlewares/github.js";
 import { subdomain } from "../util.js";
 import auth from "./auth.js";
@@ -20,8 +18,5 @@ export const installApiRouter = (app: Application) => {
   router.use(auth);
   router.use(stripe);
 
-  Sentry.setupExpressErrorHandler(router);
-  router.use(errorHandler());
-
   app.use(subdomain(router, "api"));
 };

apps/backend/src/web/app-router.ts

@@ -1,6 +1,5 @@
 import { join } from "node:path";
 import { invariant } from "@argos/util/invariant";
-import * as Sentry from "@sentry/node";
 import express, { Router, static as serveStatic } from "express";
 import { rateLimit } from "express-rate-limit";
 
@@ -109,5 +108,4 @@ export const installAppRouter = async (app: express.Application) => {
   });
 
   app.use(subdomain(router, "app"));
-  Sentry.setupExpressErrorHandler(router);
 };

apps/backend/src/web/app.ts

@@ -11,6 +11,7 @@ import config from "@/config/index.js";
 
 import { installApiRouter } from "./api/index.js";
 import { installAppRouter } from "./app-router.js";
+import { jsonErrorHandler } from "./middlewares/errorHandler.js";
 
 const __dirname = fileURLToPath(new URL(".", import.meta.url));
 
@@ -90,5 +91,8 @@ export const createApp = async () => {
   installApiRouter(app);
   await installAppRouter(app);
 
+  Sentry.setupExpressErrorHandler(app);
+  app.use(jsonErrorHandler());
+
   return app;
 };

apps/backend/src/web/middlewares/errorHandler.ts

@@ -1,15 +1,16 @@
 import type { ErrorRequestHandler } from "express";
 
-export function errorHandler() {
-  const handlers: ErrorRequestHandler[] = [
-    (error, _req, _res, next) => {
-      if (process.env["NODE_ENV"] !== "test") {
-        console.log(error, error.stack);
-      }
-      next(error);
-    },
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    (error: unknown, _req, res, _next) => {
+/**
+ * A middleware that sends JSON responses for errors if request accepts JSON.
+ */
+export function jsonErrorHandler(): ErrorRequestHandler {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  return (error: unknown, req, res, next) => {
+    if (error instanceof Error && process.env["NODE_ENV"] !== "test") {
+      console.log(error, error.stack);
+    }
+
+    if (req.accepts("json") === "json") {
       const statusCode =
         error instanceof Error &&
         "statusCode" in error &&
@@ -24,18 +25,23 @@ export function errorHandler() {
                 typeof error.code === "number"
               ? error.code
               : 500;
+
       const message =
         error instanceof Error ? error.message : "Internal Server Error";
+
       const code =
         error instanceof Error && "code" in error ? error.code : undefined;
+
       res.status(statusCode);
-      return res.send({
+
+      res.send({
         error: {
           message,
           code,
         },
       });
-    },
-  ];
-  return handlers;
+    } else {
+      next(error);
+    }
+  };
 }