1872671 - Improve error message for ambiguous indirect export

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P3)

Description

[Sebastian Zartner [:sebo]]

Attachment: Simple test case

When trying to import the default export of a module that doesn't provide one, the error message currently says this:

Uncaught SyntaxError: ambiguous indirect export: default

The meaning of this message is unclear and it doesn't provide proper information on how to fix the error.

Chrome's error message is a little more explicit here:

Uncaught SyntaxError: The requested module './module.js' does not provide an export named 'default'

Sebastian

Comment 1

[Sebastian Zartner [:sebo]]

Attachment: test.js

Comment 2

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi]]

Attachment: Bug 1872671 - Fix error message when import failed.

Fix the wrong order of error number in ErrorNumbers.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e85cad69c36f
Fix error message when import failed. r=jonco

Comment 4

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/e85cad69c36f

Comment 5

[Sebastian Zartner [:sebo]]

While the change seems to fix a bug regarding which error message is displayed, the error messages themselves still lack important information how to fix the issues.

Given the attached example, I now get this error message:

Uncaught SyntaxError: import not found: default

They should provide authors with a hint what they need to change in order to fix the error.

The error message should rather provide the info about the module not providing a default export. Given the example, I'd expect something like

Uncaught SyntaxError: The requested module 'https://cdnjs.cloudflare.com/ajax/libs/ajv/8.12.0/ajv7.min.js' does not provide a default export.

And when trying to import a non-existing export, you could have the same message as Chrome provides it, i.e.

The requested module 'https://cdnjs.cloudflare.com/ajax/libs/ajv/8.12.0/ajv7.min.js' does not provide an export named 'foo'.

And for the ambiguous test case in the patch, the message still says

Uncaught SyntaxError: ambiguous indirect export: a

While that message should rather read like

Uncaught SyntaxError: The requested module './export_ambiguous.mjs' contains ambiguous star exports for name 'a' of imported modules './exportA1.mjs' and './exportA2.mjs'.

That would make it much easier to debug those exports and imports.

Sebastian

Comment 6

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi]]

Hi, Sebastian
This bug we do have fixed the error message, it was showing the wrong error message which caused the confusion.
To address your comment 5, I have filed a new bug for this, bug 1873610.