jest: The original function name gets lost in the Jest error stack

test('hello world', () => {
 function BadCode() {
    throw new Error('noo')
  }

  function run(fn) {
    fn()
  }

  run(BadCode)
});

I expect to see BadCode in the stack because it’s a named function. But it shows up as fn instead:

      at fn (sum.test.js:3:11)
      at run (sum.test.js:7:5)
      at Object.<anonymous> (sum.test.js:10:3)

Same with error.stack property.

Isn’t this just a Node issue?

Nope, try it in Node REPL and see BadCode:

Uncaught Error: noo
    at BadCode (repl:2:11)
    at run (repl:2:5)

Also works correctly in Chrome.

I’ve done both locally so I used the same Node version (12.18.3). So it’s Jest-specific.

I can also reproduce this on Repl.it: https://repl.it/repls/SecondaryItchyGui

I’ve tried vm.runInContext locally but that did not trigger the issue. I also verified I’m not transpiling anything. So I have no idea what is the cause of this. The underlying bug is probably in Node or V8 but we need to figure out what is special about Jest that is triggering it.

Why fix this?

This affects the new React component stack printing strategy so it would be unfortunate for this to stay unfixed very long.

About this issue

Original URL
State: open
Created 4 years ago
Comments: 18 (16 by maintainers)

Most upvoted comments

This “fixes” the reproduction

diff --git i/yarn.lock w/yarn.lock
index 3d75ffc..d290b3c 100644
--- i/yarn.lock
+++ w/yarn.lock
@@ -3019,9 +3019,9 @@ source-map-resolve@^0.5.0:
     urix "^0.1.0"
 
 source-map-support@^0.5.6:
-  version "0.5.19"
-  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.19.tgz#a98b62f86dcaf4f67399648c085291ab9e8fed61"
-  integrity sha512-Wonm7zOCIJzBGQdB+thsPar0kYuCIzYvxZwlBa87yi/Mdjv7Tip2cyVbLj5o0cFPN4EVkuTwb3GDDyUx2DGnGw==
+  version "0.5.13"
+  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.13.tgz#31b24a9c2e73c2de85066c0feb7d44767ed52932"
+  integrity sha512-SHSKFHadjVA5oR4PPqhtAVdcBWwRYVd6g6cAXnIbRiIwc2EhPrTuKUBdSLvlEKyIP3GCf89fltvcZiP9MMFA1w==
   dependencies:
     buffer-from "^1.0.0"
     source-map "^0.6.0"

So related to #9147 somehow is my guess

Adding "jest": {"transform": {}} to package.json also “fixes” it, fwiw

SimenB on Oct 14, 2020

@flozender’s repo works (or doesn’t… It reproduces the bug, is what I’m trying to say)

SimenB on Oct 14, 2020

@SimenB I tried the same and got fn:

  ✕ hello world (2 ms)

  ● hello world

    noo

      1 | test("hello world", () => {
      2 |   function BadCode() {
    > 3 |     throw new Error("noo");
        |           ^
      4 |   }
      5 | 
      6 |   function run(fn) {

      at fn (__tests__/index.test.js:3:11)
      at run (__tests__/index.test.js:7:5)
      at Object.<anonymous> (__tests__/index.test.js:10:3)

Node: v12.19.0 Jest: v26.5.3

flozender on Oct 14, 2020

Hmm, maybe not. @gaearon did you test with latest version of Jest? Repl.it is on 24 by default This is what I’m seeing running your example in jest@26.5.2 (node 12.19.0)

  ✕ hello world (3 ms)

  ● hello world

    noo

      1 | test('hello world', () => {
      2 |   function BadCode() {
    > 3 |     throw new Error('noo');
        |           ^
      4 |   }
      5 |
      6 |   function run(fn) {

      at BadCode (test.js:3:11)
      at fn (test.js:7:5)
      at Object.run (test.js:10:3)

SimenB on Oct 14, 2020

Go for it 🙂

SimenB on Oct 14, 2020

Would love to give it a shot!

flozender on Oct 14, 2020