1513028 - Loader throws empty exceptions when a module doesn't exists

Status: RESOLVED FIXED

(DevTools :: Framework, enhancement, P2)

Description

[Alexandre Poirot [:ochameau]]

While trying to migrate the debugger to es modules, I was seeing various errors like this in the console, without any stack:
  JavaScript error: undefined, line 0: Error

The best unactionable error report you could get!
After some investigations I figured out it was because of the loader throwing empty exception from here:
  https://searchfox.org/mozilla-central/source/devtools/shared/base-loader.js#258

When a module path is wrong, loadSubScript throws a string exception.
It is already bad as string exceptions:
  throw "exception"
don't come with any stack, nor any location.

The loader somehow tries to handle that, but fails.

Comment 1

[Alexandre Poirot [:ochameau]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=1ab6d5542ee59908fbc26ecb64286a44b0275351

Comment 2

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1513028 - Throw exception with stack and message when a module doesn't exists.

loadSubScript throws a string, without any stack/location.
Consider all string exceptions as coming from loadSubScript and re-throw a real error
object, coming with the stack of the require call.
Also handle wrong require path with a more explicit error message.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5e3e0441c856
Throw exception with stack and message when a module doesn't exists. r=jdescottes

Comment 4

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/5e3e0441c856