1680228 - Some variables show undefined when they are not

Status: RESOLVED WORKSFORME

(DevTools :: Debugger, defect, P3)

Description

[David]

Attachment: Sin título.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:83.0) Gecko/20100101 Firefox/83.0

Steps to reproduce:

1. Go to https://getbootstrap.com/docs/4.0/components/dropdowns/
2. Go to Debugger (press F12)
3. Create a breakpoint in dropdown.js#181
4. Click on "Dropdown button" ( You need to do a little scroll )
5. Constant ClassName shows as undefined

Comment 1

[Hubert Boma Manilla (:bomsy)]

Thanks for reporting!
I can reproduce the issue.

Comment 2

[Zac Svoboda :zacnomore]

Attachment: Example of mapped values

Played with this for a while, tried to reduce the testcase but I didn't manage to reproduce this in a glitch.
However, I'd like to point out some other anomalies and speculate wildly. If you take a look at this screenshot you can see that ClassName.SHOW value does actually exist as h along with all the others under scope W. Seems to make sense as the script does manage to run fine without error.
It seems to me that something is messed up during optimization that breaks the connection between the script as written and the optimized version.

Comment 3

[Hubert Boma Manilla (:bomsy)]

Attachment: map scopes.png

Thanks for reporting!

This relates to Map Scopes feature not been switched on. See the screen shot. Once the box is checked the preview value should show correctly.

Also see the documentation https://firefox-source-docs.mozilla.org/devtools-user/debugger/using_the_debugger_map_scopes_feature/index.html

It's clear this feature might not be too discoverable by users, we'll look into improving this See https://bugzilla.mozilla.org/show_bug.cgi?id=1695621#c1 for details.

Comment 4

[Hubert Boma Manilla (:bomsy)]

Closing this bug now as noting to fix here. Feel free to reopen if there are specifics.