Error `cause` is not displayed

[OliverJAsh]

package.json:

{
  "dependencies": {
    "express": "^4.19.2"
  }
}

server.js:

const express = require("express");

const app = express();

app.get("/", (req, res) => {
  throw new Error("foo", {
    cause: new Error("bar"),
  });
});

app.listen(3000, () => {
  console.log("Server is running on port 3000");
});

$ node server.js
Server is running on port 3000

$ curl "localhost:3000"

Actual

The error cause is not displayed.

Error: foo
    at /Users/oliver/Code/reduced-test-cases/express-error-cause/server.js:6:9
    at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)
    at next (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/route.js:149:13)
    at Route.dispatch (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/route.js:119:3)
    at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)
    at /Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/index.js:284:15
    at Function.process_params (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/index.js:346:12)
    at next (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/index.js:280:10)
    at expressInit (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/middleware/init.js:40:5)
    at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)

Expected

The error cause should be displayed, like it is for exceptions occurring outside of request handlers.

Error: foo
    at /Users/oliver/Code/reduced-test-cases/express-error-cause/server.js:6:9
    at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)
    ... 7 lines matching cause stack trace ...
    at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5) {
  [cause]: Error: bar
      at /Users/oliver/Code/reduced-test-cases/express-error-cause/server.js:7:12
      at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)
      at next (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/route.js:149:13)
      at Route.dispatch (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/route.js:119:3)
      at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)
      at /Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/index.js:284:15
      at Function.process_params (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/index.js:346:12)
      at next (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/index.js:280:10)
      at expressInit (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/middleware/init.js:40:5)
      at Layer.handle [as handle_request] (/Users/oliver/Code/reduced-test-cases/express-error-cause/node_modules/express/lib/router/layer.js:95:5)
}

[wesleytodd]

Hey @OliverJAsh, thanks for the report. The specification for error causes is comparatively new to the code which handles this and the error stack is what we use for displaying this. I do agree though that showing error causes for development logging would be an awesome improvement. Feel free to open a PR for this one.

[shubham9069]

Hii @OliverJAsh thanks for the report. can you able to compile this enhancement?

[DanielBelz1997]

hey, i want to contribute to this enhancement. there is any way to connect this issue to me?

[wesleytodd]

Hey @DanielBelz1997, we would love a PR for this. The stack trace behavior comes from finalhandler here, that is the best place to start if you would like to work on this.

[DanielBelz1997]

thanks for the quick reply! i will get right into it

[DanielBelz1997]

fixed the issue. but the code is in the finalHandler package. how should i do a PR on this?

[wesleytodd]

Open a PR to finalhandler and mention this issue in the description of the PR.

[coltonehrman]

I created a small reproduction/test for this 👀 https://github.com/coltonehrman/bag-of-tools/blob/main/examples/express/error-stack-trace/error.test.ts

[wesleytodd]

I have a review out on both of these PRs. Whoever gets theirs into a fixed up state I will merge and publish. Closing this to track work on this in the respective PRs.