From 382a42d4393a1b457620eb5fb50fc7805e007624 Mon Sep 17 00:00:00 2001
From: Stephan <57194608+stephan418@users.noreply.github.com>
Date: Wed, 27 Apr 2022 15:30:55 +0200
Subject: [PATCH] Add basic error handling

+ Add express-async-errors package to handle async errors
+ Add ForwaradableError class (Base class for all project-specific errors)
+ Add defaultErrorHandler middleware which handles errors and sends info to the client
---
 package.json                             |  1 +
 src/Middleware/error/ForwardableError.ts | 16 +++++++++++
 src/Middleware/error/handler.ts          | 36 ++++++++++++++++++++++++
 src/app.ts                               |  7 +++++
 4 files changed, 60 insertions(+)
 create mode 100644 src/Middleware/error/ForwardableError.ts
 create mode 100644 src/Middleware/error/handler.ts

diff --git a/package.json b/package.json
index 4166d94..9bbdaf3 100644
--- a/package.json
+++ b/package.json
@@ -27,6 +27,7 @@
     "argon2": "^0.28.2",
     "dotenv": "^10.0.0",
     "express": "^4.17.1",
+    "express-async-errors": "^3.1.1",
     "jsonwebtoken": "^8.5.1",
     "nodemailer": "^6.7.0",
     "redis": "^3.1.2"
diff --git a/src/Middleware/error/ForwardableError.ts b/src/Middleware/error/ForwardableError.ts
new file mode 100644
index 0000000..04bc5e1
--- /dev/null
+++ b/src/Middleware/error/ForwardableError.ts
@@ -0,0 +1,16 @@
+export default class ForwardableError extends Error {
+  // If in different context
+  private readonly __id = "CUSTOM_ERROR";
+
+  public readonly status: number;
+
+  constructor(status: number, message: string) {
+    super(message);
+
+    this.status = status;
+  }
+
+  static isForwardableError(error: any): error is ForwardableError {
+    return error.__id === "CUSTOM_ERROR";
+  }
+}
diff --git a/src/Middleware/error/handler.ts b/src/Middleware/error/handler.ts
new file mode 100644
index 0000000..d182f19
--- /dev/null
+++ b/src/Middleware/error/handler.ts
@@ -0,0 +1,36 @@
+import { PrismaClientUnknownRequestError } from "@prisma/client/runtime";
+import { NextFunction, Request, Response } from "express";
+import ForwardableError from "./ForwardableError";
+
+const env = process.env.NODE_ENV || "production";
+
+export default function defaultErrorHandler(err: any, req: Request, res: Response, next: NextFunction) {
+  if (ForwardableError.isForwardableError(err)) {
+    return res.status(err.status).json({
+      type: "error",
+      payload: {
+        message: err.message,
+        ...(env === "development"
+          ? {
+              stack: err.stack,
+            }
+          : {}),
+      },
+    });
+  }
+
+  if (err instanceof PrismaClientUnknownRequestError) {
+    return res.status(404).json({
+      type: "error",
+      payload: {
+        message: "An unknown error occured. This could be due to malformed IDs",
+        ...(env === "development"
+          ? {
+              prisma: err.message,
+              stack: err.stack,
+            }
+          : {}),
+      },
+    });
+  }
+}
diff --git a/src/app.ts b/src/app.ts
index bb3b56b..83e28d1 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -6,6 +6,10 @@ import argon2 from "argon2";
 import adminRouter from "./Routes/admin.routes";
 import organisationRouter from "./Routes/organisation.routes";
 import groupRouter from "./Routes/group.routes";
+import defaultErrorHandler from "./Middleware/error/handler";
+
+// Set up async error handling
+require("express-async-errors");
 
 require("dotenv").config(); // Load dotenv config
 
@@ -52,6 +56,9 @@ async function main() {
 
   app.use("/api/groups", groupRouter);
 
+  // Error handling
+  app.use(defaultErrorHandler);
+
   app.listen(process.env.PORT, () => {
     console.log(`Listening on Port: ${process.env.PORT}`);
   });